Diane Beckles - Profile on Academia.edu (original) (raw)
Papers by Diane Beckles
Postharvest internal browning of pineapple fruit originates at the phloem
Journal of Plant Physiology, 2016
A typical symptom of postharvest chilling injury (PCI) in pineapple fruit (Ananas comosus (L.) Me... more A typical symptom of postharvest chilling injury (PCI) in pineapple fruit (Ananas comosus (L.) Merr.) is internal browning (IB) near the fruit core. Since vascular bundles (VBs) are localized to this region, it was hypothesized that the VBs might be the site of IB. To test this, the anatomy and histochemistry of VBs during chilling stress in four pineapple cultivars with different levels of sensitivity to PCI were examined. Fruit were stored at 10°C for up to three weeks to stimulate translucency symptoms (TS; the initiation of IB). After three weeks of chilling exposure, the cultivars 'MD2' showed 0%, 'Pattavia' and 'Savee' showed 10-16%, and 'Trad Sri Thong' showed 100% TS and IB symptom. Scanning electron microscopy and in situ histochemical staining techniques that detect enzymes and substrates commonly associated with IB initiation were used in parallel. The TS of pineapple fruit coincided with the collapse of the phloem tissue. The VBs in the tissue where IB was initiated (i.e., the flesh adjacent to the core or F/C) had the highest activity of polyphenol oxidase, hydrogen peroxide, and phenolic compounds. The IB-resistant 'MD2' genotype had fewer VBs, but a greater proportion of sclerenchyma fibers (P<0.05) than did the susceptible 'Trad Sri Thong'. Based on these data, the first report of pineapple IB occurrence in the phloem was proposed.
Journal of Stored Products and Postharvest Research, Oct 31, 2013
Chilling-sensitive fruits often produce a burst of ethylene when reconditioned at ambient tempera... more Chilling-sensitive fruits often produce a burst of ethylene when reconditioned at ambient temperature after cold storage. This has led some researchers to propose that chilling injury (CI) may be induced by post-chilling ethylene production. To test this hypothesis, we examined two tomato (Solanum lycopersicon L.) mutants, non-ripening (nor) and ripening-inhibitor (rin), that do not produce climacteric ethylene, after they were subjected to cold-storage and reconditioning. The response of the mutants differed, and was not as extreme as the parent line cv. Ailsa Craig, but both showed symptoms of chilling stress. Therefore while ethylene production may influence chilling injury, it is not essential for initiating this process in tomato cv. Ailsa Craig.
Postharvest Biology and Technology, 2012
Chilling-sensitive fruit often produce a burst of ethylene when reconditioned at ambient temperat... more Chilling-sensitive fruit often produce a burst of ethylene when reconditioned at ambient temperature after cold storage. This has led some authors to propose that chilling injury (CI) may be induced by post-chilling ethylene production. To test this hypothesis we examined two tomato (Solanum lycopersicum L.) mutants, non-ripening (nor) and ripening-inhibitor (rin) that do not produce climacteric ethylene. Fruit were stored at 5°C followed by reconditioning at 20°C, during which time a detailed characterisation of respiration, ethylene production, colour analysis, firmness, total soluble solids, starch content and weight loss was done. The response of the mutants to cold-storage at 5°C differed, and was not as extreme as the parent line cv. Ailsa Craig, still, both mutants showed symptoms of chilling stress on the ripening pathways that are initiated upstream of climacteric ethylene production. When the fruit were stored at 2.5°C for 14 days followed by reconditioning at 20°C for 3 weeks, visual evidence of CI such as water-soaking, non-uniform ripening and minimal colour change was noted in both the control and mutant genotypes. We conclude therefore that while ethylene production may influence chilling injury, it is not essential for initiating this process in tomato cv. Ailsa Craig.
This invention relates to an isolated nucleic acid fragment encoding a starch synthase DUI homolo... more This invention relates to an isolated nucleic acid fragment encoding a starch synthase DUI homolog. The invention also relates to the construction of a chimeric gene encoding all or a portion of the starch synthase DUI homolog, in sense or antisense orientation, Wherein expression of the chimeric gene results in production of altered levels of the starch synthase DUI homolog in a transformed host cell.
Plant Metabolomics - Applications and opportunities for agricultural biotechnology
In this chapter we will outline what is known about the general organization of metabolite networ... more In this chapter we will outline what is known about the general organization of metabolite networks and use it to illustrate broad concepts of metabolic control and regulation, information necessary for metabolite engineering. We will then survey the analytical and data-mining tools available as this will allow us to ascertain what can be measured and how biological information can be extracted from these measurements. We will then outline how metabolomics is being used to support biotechnology. There has literally been an explosion in the number, scope, and depth of applications of metabolomics in recent years and we will not be able to comprehensively address them all. Finally, we will look at the challenges ahead and the key issues that must be addressed if the full potential of this discipline is to be realized for improving agriculture.
Increasing resistant starch in wheat using TILLING
CFW Plexus, 2013
Postharvest Biology and Technology, 2012
Chilling-sensitive fruit often produce a burst of ethylene when reconditioned at ambient temperat... more Chilling-sensitive fruit often produce a burst of ethylene when reconditioned at ambient temperature after cold storage. This has led some authors to propose that chilling injury (CI) may be induced by post-chilling ethylene production. To test this hypothesis we examined two tomato (Solanum lycopersicum L.) mutants, non-ripening (nor) and ripening-inhibitor (rin) that do not produce climacteric ethylene. Fruit were stored at 5°C followed by reconditioning at 20°C, during which time a detailed characterisation of respiration, ethylene production, colour analysis, firmness, total soluble solids, starch content and weight loss was done. The response of the mutants to cold-storage at 5°C differed, and was not as extreme as the parent line cv. Ailsa Craig, still, both mutants showed symptoms of chilling stress on the ripening pathways that are initiated upstream of climacteric ethylene production. When the fruit were stored at 2.5°C for 14 days followed by reconditioning at 20°C for 3 weeks, visual evidence of CI such as water-soaking, non-uniform ripening and minimal colour change was noted in both the control and mutant genotypes. We conclude therefore that while ethylene production may influence chilling injury, it is not essential for initiating this process in tomato cv. Ailsa Craig.
Plant Biotechnology and Agriculture, 2012
Contributors
Plant Biotechnology and Agriculture, 2012
The aim of this work was to examine agronomic, compositional, and functional changes in rice (Ory... more The aim of this work was to examine agronomic, compositional, and functional changes in rice (Oryza sativa L. cv. Nipponbare) grains from plants grown under low-to-moderate salinity stress. Plants were grown in sodium chloride-containing soil (2 or 4 dS/m2 electrical conductivity), which was imposed 4-weeks after transplant (called Seedling EC2 and EC4) or after the appearance of the anthers (called Anthesis EC2 and EC4). The former simulates field conditions while the latter permits observation of the isolated effect of salt on grain filling processes. Key findings of this study are that: (i) Plants showed adaptive responses to prolonged salt treatment with no negative effects on grain weight or fertility. Seedling EC2 plants had more panicles and enhanced caryopsis dimensions, while surprisingly, Anthesis EC4 plants did not differ from the control group in the agronomic parameters measured. (ii) Grain starch increased in Seedling EC4 (32.6%) and Anthesis EC2 (39%) respectively, suggesting a stimulatory effect of salt on starch accumulation. (iii) The salinity treatment of 2 dS/m2 was better tolerated at anthesis than the 4 dS/m2 treatment as the latter led to reduced grain weight (28.8%) and seed fertility (19.4%) and compensatory increases in protein (20.1%) and Nitrogen contents (19.8%). (iv) Although some salinity treatments led to changes in starch content, these did not alter starch fine structure, morphology, or composition. We observed no differences in sugar and amylose content or starch granule size distribution among any of the treatments. The only alterations in starch were limited to small changes in thermal properties and glucan chain distribution, which were only seen in the Anthesis EC4 treatment. This similarity of compositional and functional features was supported by multivariate analysis of all variables measured, which suggested that differences due to treatments were minimal. Overall, this study documents the specific response of rice under defined conditions, and illustrates that the plasticity of plant response to mild stress is complex and highly context-dependent, even under greenhouse conditions in which other potential environmental stress impacts are minimized.
The starch accumulated in rice, wheat, maize, sorghum, and millet grain is indispensible for huma... more The starch accumulated in rice, wheat, maize, sorghum, and millet grain is indispensible for human survival
as it accounts for most of the consumed calories. In addition, cereal starch is used in its natural or modified
state as a healthful food, and as an environmentally friendly additive or replacement for petroleum-derived
fuel and polymers. Therefore, developing cereals that accumulate higher endosperm starch and starches
with novel polymeric properties could help to meet the dual challenges of sustaining human population
growth needs while minimizing some of the harmful environmental impacts. Despite its fundamental importance,
comparatively little is known about the mechanistic basis of starch biosynthesis. This entry provides a
basic overview of the “starch field” for the beginner. First, the various uses of starch, its structural organization
and biosynthesis, and how its functionality relates to its structure are outlined. Second, how recent biotechnological
advancements are leading to the discovery of new genes that modulate starch and to novel
starches generated through genetic engineering are described. Finally, some of the remaining questions
and challenges that must be tackled in order to meet the goal of increasing starch production for use as a
food, feed, fiber, and polymer in the next 50 years and beyond are illustrated
Magnetic resonance imaging (MRI) was used to monitor internal changes in harvested tomato (Solanu... more Magnetic resonance imaging (MRI) was used to monitor internal changes in harvested tomato (Solanum lycopersicum L. cv. Micro-Tom) fruit. Measurements of ethylene evolution, respiration, and ion leakage indicated that the fruit developed chilling injury (CI) after storage at 0 • C. Unlike these measurements, MRI provided spatially resolved data. The apparent diffusion coefficient (ADC), which is an indication of water mobility in tissues, was calculated from MRIs of the different parts of the fruit. Storage for 1 or 2 weeks at 0 • C caused no difference in the ADCs (D-values) in the pericarp, but it did lead to higher values in the inner tissues i.e., the columella and locular region compared to non-chilled fruit (P < 0.05). Changes in inner fruit D-values after 1 and 2 weeks of chilling at 0 • C were similar to changes in respiration, ethylene production and ion leakage which increased (P < 0.05) compared to the non-chilled controls. Most CI studies of tomato fruit used pericarp tissue. Our data indicate that columella tissue changes occur in response to chilling injury in tomato fruit and suggest that more caution is needed when interpreting data from experiments commonly used to study this phenomenon.
Low temperature storage Modified atmosphere packaging (MAP) High oxygen transmission rate-OTR a b
Cultured microalgae are viewed as important producers of lipids and polysaccharides, both of whic... more Cultured microalgae are viewed as important producers of lipids and polysaccharides, both of which are precursor molecules for the production of biofuels. This study addressed the impact of elevated carbon dioxide (CO 2 ) on Chlorella sorokiniana production of starch and on several properties of the starch produced. The production of C. sorokiniana biomass, lipid and starch were enhanced when cultures were supplied with 2% CO 2 . Starch granules from algae grown in ambient air and 2% CO 2 were analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The granules from algae grown in 2% CO 2 were disk-shaped and contained mainly stromal starch; granules from cultures grown in ambient air were cup-shaped with primarily pyrenoid starch. The granules from cells grown in 2% CO 2 had a higher proportion of the accumulated starch as the highly branched, amylopectin glucan than did granules from cells grown in air. The rate of hydrolysis of starch from 2% CO 2 -grown cells was 1.25 times greater than that from air-grown cells and 2-11 times higher than the rates of hydrolysis of starches from cereal grains. These data indicate that culturing C. sorokiniana in elevated CO 2 not only increases biomass yield but also improves the structure and composition of starch granules for use in biofuel generation. These modifications in culture conditions increase the hydrolysis efficiency of the starch hydrolysis, thus providing potentially important gains for biofuel production.
Journal of Cereal …, Jan 1, 2012
The aim of this review is to examine how the quantity and quality of starch in cereal endosperm i... more The aim of this review is to examine how the quantity and quality of starch in cereal endosperm is affected by abiotic stress. This is important because starch is the primary food source for humans, and its accumulation in cereal endosperm is a fundamental component of yield. Grain yield; however, is constrained under environmental stress with negative ramifications for agricultural productivity and sustainability. This is a significant and likely to be growing problem given that weather patterns are predicted to become increasingly extreme. In this review, we first describe starch structure and biosynthesis in the developing endosperm. Next, we outline how starch biosynthesis, content and composition are altered in response to drought, temperature extremes, salinity, nitrogen deficiency, elevated carbon dioxide and acidity. Our focus will be on the enzymes involved in the conversion of sucrose-to-starch, and how their activity is regulated at the transcriptional and post-translational level in response to certain stress. We then suggest experimental approaches for developing cereal germplasm that maintains productivity and grain quality under sub-optimal conditions. Finally, we conclude that there is an urgent need to elucidate the regulatory mechanisms that modulate starch biosynthetic enzyme activity in response to environmental extremes.
Introduction. Consumers and processors value tomatoes with high fruit sugar content; however, mos... more Introduction. Consumers and processors value tomatoes with high fruit sugar content; however, most breeding and cultural practices negatively impact this trait. Wild tomato species can accumulate two-to three-fold more fruit sugar than cultivars and are proving to be valuable both as a source of high-sugar loci to broaden the genetic base of currently produced cultivars, and as research material to understand this trait. Synthesis. While cutting-edge genomic approaches have taught us much about fruit phenotypes, it is still important to assess fruit enzyme activities and metabolic fluxes in lines with contrasting fruit sugar accumulation. These metabolic functions are closest to the ripe fruit sugar trait. In this review, we focus our attention on the biochemical pathways, especially starch biosynthesis, that may influence tomato fruit sugars. We try where possible to put this information into a physiological context because together they influence yield. We compare and contrast sugar metabolism in cultivars and wild tomato species and identify factors that may influence differences in their fruit size. Conclusion. Although difficult, we show that it is possible to develop fruit with high horticultural yield and use the breeding line 'Solara' as an example. In addition, we suggest avenues of further investigation to understand the regulation and control of fruit carbohydrate content.
The effects of engineering higher levels of the High Molecular Weight Glutenin Dx5 subunit on sta... more The effects of engineering higher levels of the High Molecular Weight Glutenin Dx5 subunit on starch characteristics in transgenic wheat (Triticum aestivum L.) grain were evaluated. This is important because of the interrelationship between starch and protein accumulation in grain, the strong biotechnological interest in modulating Dx5 levels and the increasing likelihood that transgenic wheat will be commercialized in the U.S. Unintended effects of Dx5 overexpression on starch could affect wheat marketability and therefore should be examined. Two controls with native levels of Dx5 were used: (i) the nontransformed Bobwhite cultivar, and (ii) a transgenic line (Bar-D) expressing a herbicide resistant (bar) gene, and they were compared with 2 transgenic lines (Dx5G and Dx5J) containing bar and additional copies of Dx5. There were few changes between Bar-D and Dx5G compared to Bobwhite. However, Dx5J, the line with the highest Dx5 protein (×3.5) accumulated 140% more hexose, 25% less starch and the starch had a higher frequency of longer amylopectin chains. These differences were not of sufficient magnitude to influence starch functionality, because granule morphology, crystallinity, amylose-to-amylopectin ratio, and the enthalpy of starch gelatinization and the amylose-lipid complex melting were similar to the control (P > 0.05). This overall similarity was borne out by Partial Least Squares-Discriminant Function Analysis, which could not distinguish among genotypes. Collectively our data imply that higher Dx5 can affect starch accumulation and some aspects of starch molecular structure but that the starches of the Dx5 transgenic wheat lines are substantially equivalent to the controls.
Postharvest Biology and …, Jan 1, 2011
Heat-shocks were used to reduce the development of chilling injury symptoms during ripening of to... more Heat-shocks were used to reduce the development of chilling injury symptoms during ripening of tomato fruit (Solanum lycopersicum L. cv. Micro-Tom). Mature green tomatoes were immersed in 30-50 • C water for 3-9 min before being chilled at 2.5 • C for 0, 0.5, 1, 2, 3, or 14 days, and then held at 20 • C for an additional 7-14 days. The affect of both heat-shock and chilling treatments were independent of fruit weight. Measured at 20 • C after 14 days of chilling, fruit exposed to 40 • C for 7 min exhibited reduced chilling injury symptoms, as measured by their advanced ripening score and decreased rate of ion leakage into an isotonic 0.2 M mannitol solution. Reduced rates of leakage from the symplastic compartment probably contributed to the 2-fold decrease in the amount of ions in the apoplastic space, when compared to the control. A subsequent paper will report the results of metabolic profiling of Micro-Tom tomato fruit subjected to treatments that significantly decreased their development of chilling injury symptoms.
Postharvest internal browning of pineapple fruit originates at the phloem
Journal of Plant Physiology, 2016
A typical symptom of postharvest chilling injury (PCI) in pineapple fruit (Ananas comosus (L.) Me... more A typical symptom of postharvest chilling injury (PCI) in pineapple fruit (Ananas comosus (L.) Merr.) is internal browning (IB) near the fruit core. Since vascular bundles (VBs) are localized to this region, it was hypothesized that the VBs might be the site of IB. To test this, the anatomy and histochemistry of VBs during chilling stress in four pineapple cultivars with different levels of sensitivity to PCI were examined. Fruit were stored at 10°C for up to three weeks to stimulate translucency symptoms (TS; the initiation of IB). After three weeks of chilling exposure, the cultivars 'MD2' showed 0%, 'Pattavia' and 'Savee' showed 10-16%, and 'Trad Sri Thong' showed 100% TS and IB symptom. Scanning electron microscopy and in situ histochemical staining techniques that detect enzymes and substrates commonly associated with IB initiation were used in parallel. The TS of pineapple fruit coincided with the collapse of the phloem tissue. The VBs in the tissue where IB was initiated (i.e., the flesh adjacent to the core or F/C) had the highest activity of polyphenol oxidase, hydrogen peroxide, and phenolic compounds. The IB-resistant 'MD2' genotype had fewer VBs, but a greater proportion of sclerenchyma fibers (P<0.05) than did the susceptible 'Trad Sri Thong'. Based on these data, the first report of pineapple IB occurrence in the phloem was proposed.
Journal of Stored Products and Postharvest Research, Oct 31, 2013
Chilling-sensitive fruits often produce a burst of ethylene when reconditioned at ambient tempera... more Chilling-sensitive fruits often produce a burst of ethylene when reconditioned at ambient temperature after cold storage. This has led some researchers to propose that chilling injury (CI) may be induced by post-chilling ethylene production. To test this hypothesis, we examined two tomato (Solanum lycopersicon L.) mutants, non-ripening (nor) and ripening-inhibitor (rin), that do not produce climacteric ethylene, after they were subjected to cold-storage and reconditioning. The response of the mutants differed, and was not as extreme as the parent line cv. Ailsa Craig, but both showed symptoms of chilling stress. Therefore while ethylene production may influence chilling injury, it is not essential for initiating this process in tomato cv. Ailsa Craig.
Postharvest Biology and Technology, 2012
Chilling-sensitive fruit often produce a burst of ethylene when reconditioned at ambient temperat... more Chilling-sensitive fruit often produce a burst of ethylene when reconditioned at ambient temperature after cold storage. This has led some authors to propose that chilling injury (CI) may be induced by post-chilling ethylene production. To test this hypothesis we examined two tomato (Solanum lycopersicum L.) mutants, non-ripening (nor) and ripening-inhibitor (rin) that do not produce climacteric ethylene. Fruit were stored at 5°C followed by reconditioning at 20°C, during which time a detailed characterisation of respiration, ethylene production, colour analysis, firmness, total soluble solids, starch content and weight loss was done. The response of the mutants to cold-storage at 5°C differed, and was not as extreme as the parent line cv. Ailsa Craig, still, both mutants showed symptoms of chilling stress on the ripening pathways that are initiated upstream of climacteric ethylene production. When the fruit were stored at 2.5°C for 14 days followed by reconditioning at 20°C for 3 weeks, visual evidence of CI such as water-soaking, non-uniform ripening and minimal colour change was noted in both the control and mutant genotypes. We conclude therefore that while ethylene production may influence chilling injury, it is not essential for initiating this process in tomato cv. Ailsa Craig.
This invention relates to an isolated nucleic acid fragment encoding a starch synthase DUI homolo... more This invention relates to an isolated nucleic acid fragment encoding a starch synthase DUI homolog. The invention also relates to the construction of a chimeric gene encoding all or a portion of the starch synthase DUI homolog, in sense or antisense orientation, Wherein expression of the chimeric gene results in production of altered levels of the starch synthase DUI homolog in a transformed host cell.
Plant Metabolomics - Applications and opportunities for agricultural biotechnology
In this chapter we will outline what is known about the general organization of metabolite networ... more In this chapter we will outline what is known about the general organization of metabolite networks and use it to illustrate broad concepts of metabolic control and regulation, information necessary for metabolite engineering. We will then survey the analytical and data-mining tools available as this will allow us to ascertain what can be measured and how biological information can be extracted from these measurements. We will then outline how metabolomics is being used to support biotechnology. There has literally been an explosion in the number, scope, and depth of applications of metabolomics in recent years and we will not be able to comprehensively address them all. Finally, we will look at the challenges ahead and the key issues that must be addressed if the full potential of this discipline is to be realized for improving agriculture.
Increasing resistant starch in wheat using TILLING
CFW Plexus, 2013
Postharvest Biology and Technology, 2012
Chilling-sensitive fruit often produce a burst of ethylene when reconditioned at ambient temperat... more Chilling-sensitive fruit often produce a burst of ethylene when reconditioned at ambient temperature after cold storage. This has led some authors to propose that chilling injury (CI) may be induced by post-chilling ethylene production. To test this hypothesis we examined two tomato (Solanum lycopersicum L.) mutants, non-ripening (nor) and ripening-inhibitor (rin) that do not produce climacteric ethylene. Fruit were stored at 5°C followed by reconditioning at 20°C, during which time a detailed characterisation of respiration, ethylene production, colour analysis, firmness, total soluble solids, starch content and weight loss was done. The response of the mutants to cold-storage at 5°C differed, and was not as extreme as the parent line cv. Ailsa Craig, still, both mutants showed symptoms of chilling stress on the ripening pathways that are initiated upstream of climacteric ethylene production. When the fruit were stored at 2.5°C for 14 days followed by reconditioning at 20°C for 3 weeks, visual evidence of CI such as water-soaking, non-uniform ripening and minimal colour change was noted in both the control and mutant genotypes. We conclude therefore that while ethylene production may influence chilling injury, it is not essential for initiating this process in tomato cv. Ailsa Craig.
Plant Biotechnology and Agriculture, 2012
Contributors
Plant Biotechnology and Agriculture, 2012
The aim of this work was to examine agronomic, compositional, and functional changes in rice (Ory... more The aim of this work was to examine agronomic, compositional, and functional changes in rice (Oryza sativa L. cv. Nipponbare) grains from plants grown under low-to-moderate salinity stress. Plants were grown in sodium chloride-containing soil (2 or 4 dS/m2 electrical conductivity), which was imposed 4-weeks after transplant (called Seedling EC2 and EC4) or after the appearance of the anthers (called Anthesis EC2 and EC4). The former simulates field conditions while the latter permits observation of the isolated effect of salt on grain filling processes. Key findings of this study are that: (i) Plants showed adaptive responses to prolonged salt treatment with no negative effects on grain weight or fertility. Seedling EC2 plants had more panicles and enhanced caryopsis dimensions, while surprisingly, Anthesis EC4 plants did not differ from the control group in the agronomic parameters measured. (ii) Grain starch increased in Seedling EC4 (32.6%) and Anthesis EC2 (39%) respectively, suggesting a stimulatory effect of salt on starch accumulation. (iii) The salinity treatment of 2 dS/m2 was better tolerated at anthesis than the 4 dS/m2 treatment as the latter led to reduced grain weight (28.8%) and seed fertility (19.4%) and compensatory increases in protein (20.1%) and Nitrogen contents (19.8%). (iv) Although some salinity treatments led to changes in starch content, these did not alter starch fine structure, morphology, or composition. We observed no differences in sugar and amylose content or starch granule size distribution among any of the treatments. The only alterations in starch were limited to small changes in thermal properties and glucan chain distribution, which were only seen in the Anthesis EC4 treatment. This similarity of compositional and functional features was supported by multivariate analysis of all variables measured, which suggested that differences due to treatments were minimal. Overall, this study documents the specific response of rice under defined conditions, and illustrates that the plasticity of plant response to mild stress is complex and highly context-dependent, even under greenhouse conditions in which other potential environmental stress impacts are minimized.
The starch accumulated in rice, wheat, maize, sorghum, and millet grain is indispensible for huma... more The starch accumulated in rice, wheat, maize, sorghum, and millet grain is indispensible for human survival
as it accounts for most of the consumed calories. In addition, cereal starch is used in its natural or modified
state as a healthful food, and as an environmentally friendly additive or replacement for petroleum-derived
fuel and polymers. Therefore, developing cereals that accumulate higher endosperm starch and starches
with novel polymeric properties could help to meet the dual challenges of sustaining human population
growth needs while minimizing some of the harmful environmental impacts. Despite its fundamental importance,
comparatively little is known about the mechanistic basis of starch biosynthesis. This entry provides a
basic overview of the “starch field” for the beginner. First, the various uses of starch, its structural organization
and biosynthesis, and how its functionality relates to its structure are outlined. Second, how recent biotechnological
advancements are leading to the discovery of new genes that modulate starch and to novel
starches generated through genetic engineering are described. Finally, some of the remaining questions
and challenges that must be tackled in order to meet the goal of increasing starch production for use as a
food, feed, fiber, and polymer in the next 50 years and beyond are illustrated
Magnetic resonance imaging (MRI) was used to monitor internal changes in harvested tomato (Solanu... more Magnetic resonance imaging (MRI) was used to monitor internal changes in harvested tomato (Solanum lycopersicum L. cv. Micro-Tom) fruit. Measurements of ethylene evolution, respiration, and ion leakage indicated that the fruit developed chilling injury (CI) after storage at 0 • C. Unlike these measurements, MRI provided spatially resolved data. The apparent diffusion coefficient (ADC), which is an indication of water mobility in tissues, was calculated from MRIs of the different parts of the fruit. Storage for 1 or 2 weeks at 0 • C caused no difference in the ADCs (D-values) in the pericarp, but it did lead to higher values in the inner tissues i.e., the columella and locular region compared to non-chilled fruit (P < 0.05). Changes in inner fruit D-values after 1 and 2 weeks of chilling at 0 • C were similar to changes in respiration, ethylene production and ion leakage which increased (P < 0.05) compared to the non-chilled controls. Most CI studies of tomato fruit used pericarp tissue. Our data indicate that columella tissue changes occur in response to chilling injury in tomato fruit and suggest that more caution is needed when interpreting data from experiments commonly used to study this phenomenon.
Low temperature storage Modified atmosphere packaging (MAP) High oxygen transmission rate-OTR a b
Cultured microalgae are viewed as important producers of lipids and polysaccharides, both of whic... more Cultured microalgae are viewed as important producers of lipids and polysaccharides, both of which are precursor molecules for the production of biofuels. This study addressed the impact of elevated carbon dioxide (CO 2 ) on Chlorella sorokiniana production of starch and on several properties of the starch produced. The production of C. sorokiniana biomass, lipid and starch were enhanced when cultures were supplied with 2% CO 2 . Starch granules from algae grown in ambient air and 2% CO 2 were analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The granules from algae grown in 2% CO 2 were disk-shaped and contained mainly stromal starch; granules from cultures grown in ambient air were cup-shaped with primarily pyrenoid starch. The granules from cells grown in 2% CO 2 had a higher proportion of the accumulated starch as the highly branched, amylopectin glucan than did granules from cells grown in air. The rate of hydrolysis of starch from 2% CO 2 -grown cells was 1.25 times greater than that from air-grown cells and 2-11 times higher than the rates of hydrolysis of starches from cereal grains. These data indicate that culturing C. sorokiniana in elevated CO 2 not only increases biomass yield but also improves the structure and composition of starch granules for use in biofuel generation. These modifications in culture conditions increase the hydrolysis efficiency of the starch hydrolysis, thus providing potentially important gains for biofuel production.
Journal of Cereal …, Jan 1, 2012
The aim of this review is to examine how the quantity and quality of starch in cereal endosperm i... more The aim of this review is to examine how the quantity and quality of starch in cereal endosperm is affected by abiotic stress. This is important because starch is the primary food source for humans, and its accumulation in cereal endosperm is a fundamental component of yield. Grain yield; however, is constrained under environmental stress with negative ramifications for agricultural productivity and sustainability. This is a significant and likely to be growing problem given that weather patterns are predicted to become increasingly extreme. In this review, we first describe starch structure and biosynthesis in the developing endosperm. Next, we outline how starch biosynthesis, content and composition are altered in response to drought, temperature extremes, salinity, nitrogen deficiency, elevated carbon dioxide and acidity. Our focus will be on the enzymes involved in the conversion of sucrose-to-starch, and how their activity is regulated at the transcriptional and post-translational level in response to certain stress. We then suggest experimental approaches for developing cereal germplasm that maintains productivity and grain quality under sub-optimal conditions. Finally, we conclude that there is an urgent need to elucidate the regulatory mechanisms that modulate starch biosynthetic enzyme activity in response to environmental extremes.
Introduction. Consumers and processors value tomatoes with high fruit sugar content; however, mos... more Introduction. Consumers and processors value tomatoes with high fruit sugar content; however, most breeding and cultural practices negatively impact this trait. Wild tomato species can accumulate two-to three-fold more fruit sugar than cultivars and are proving to be valuable both as a source of high-sugar loci to broaden the genetic base of currently produced cultivars, and as research material to understand this trait. Synthesis. While cutting-edge genomic approaches have taught us much about fruit phenotypes, it is still important to assess fruit enzyme activities and metabolic fluxes in lines with contrasting fruit sugar accumulation. These metabolic functions are closest to the ripe fruit sugar trait. In this review, we focus our attention on the biochemical pathways, especially starch biosynthesis, that may influence tomato fruit sugars. We try where possible to put this information into a physiological context because together they influence yield. We compare and contrast sugar metabolism in cultivars and wild tomato species and identify factors that may influence differences in their fruit size. Conclusion. Although difficult, we show that it is possible to develop fruit with high horticultural yield and use the breeding line 'Solara' as an example. In addition, we suggest avenues of further investigation to understand the regulation and control of fruit carbohydrate content.
The effects of engineering higher levels of the High Molecular Weight Glutenin Dx5 subunit on sta... more The effects of engineering higher levels of the High Molecular Weight Glutenin Dx5 subunit on starch characteristics in transgenic wheat (Triticum aestivum L.) grain were evaluated. This is important because of the interrelationship between starch and protein accumulation in grain, the strong biotechnological interest in modulating Dx5 levels and the increasing likelihood that transgenic wheat will be commercialized in the U.S. Unintended effects of Dx5 overexpression on starch could affect wheat marketability and therefore should be examined. Two controls with native levels of Dx5 were used: (i) the nontransformed Bobwhite cultivar, and (ii) a transgenic line (Bar-D) expressing a herbicide resistant (bar) gene, and they were compared with 2 transgenic lines (Dx5G and Dx5J) containing bar and additional copies of Dx5. There were few changes between Bar-D and Dx5G compared to Bobwhite. However, Dx5J, the line with the highest Dx5 protein (×3.5) accumulated 140% more hexose, 25% less starch and the starch had a higher frequency of longer amylopectin chains. These differences were not of sufficient magnitude to influence starch functionality, because granule morphology, crystallinity, amylose-to-amylopectin ratio, and the enthalpy of starch gelatinization and the amylose-lipid complex melting were similar to the control (P > 0.05). This overall similarity was borne out by Partial Least Squares-Discriminant Function Analysis, which could not distinguish among genotypes. Collectively our data imply that higher Dx5 can affect starch accumulation and some aspects of starch molecular structure but that the starches of the Dx5 transgenic wheat lines are substantially equivalent to the controls.
Postharvest Biology and …, Jan 1, 2011
Heat-shocks were used to reduce the development of chilling injury symptoms during ripening of to... more Heat-shocks were used to reduce the development of chilling injury symptoms during ripening of tomato fruit (Solanum lycopersicum L. cv. Micro-Tom). Mature green tomatoes were immersed in 30-50 • C water for 3-9 min before being chilled at 2.5 • C for 0, 0.5, 1, 2, 3, or 14 days, and then held at 20 • C for an additional 7-14 days. The affect of both heat-shock and chilling treatments were independent of fruit weight. Measured at 20 • C after 14 days of chilling, fruit exposed to 40 • C for 7 min exhibited reduced chilling injury symptoms, as measured by their advanced ripening score and decreased rate of ion leakage into an isotonic 0.2 M mannitol solution. Reduced rates of leakage from the symplastic compartment probably contributed to the 2-fold decrease in the amount of ions in the apoplastic space, when compared to the control. A subsequent paper will report the results of metabolic profiling of Micro-Tom tomato fruit subjected to treatments that significantly decreased their development of chilling injury symptoms.