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Papers by william asiche

Peel degreening is an important aspect of fruit ripening in many citrus fruit, and earlier studie... more Peel degreening is an important aspect of fruit ripening in many citrus fruit, and earlier studies have shown that it can be advanced either by ethylene treatment or during low temperature storage. However, the important regulators and pathways involved in natural peel degreening remain largely unknown. To understand how natural peel degreening is regulated in lemon (Citrus limon L.) fruit, flavedo transcriptome and physiochemical changes in response to either ethylene treatment or low temperature were studied. Ethylene treatment induced rapid peel degreening which was strongly inhibited by the ethylene antagonist, 1-methylcyclopropene (1-MCP). Compared with 25°C, moderately low temperatures (5°C, 10°C, 15°C and 20°C) also triggered peel degreening. Surprisingly, repeated 1-MCP treatments failed to inhibit the peel degreening induced by low temperature. Transcriptome analysis revealed that low temperature and ethylene independently regulated genes associated with chlorophyll degrada...

Frontiers in Plant Science

Peel degreening is the most conspicuous aspect of fruit ripening in many citrus fruits because of... more Peel degreening is the most conspicuous aspect of fruit ripening in many citrus fruits because of its importance for marketability. In this study, peel degreening in response to propylene (an ethylene analog) and at varying storage temperatures was characterized in Satsuma mandarin (Citrus unshiu Marc.) fruit. Propylene treatment triggered rapid peel degreening (within 4–6 days), indicated by an increase in the citrus color index (CCI) and chlorophyll loss. Peel degreening was also observed in fruit at 10°C and 15°C after 28–42 days, with gradual CCI increase and chlorophyll reduction. However, fruit at 5°C, 20°C, and 25°C remained green, and no substantial changes in peel CCI and chlorophyll content were recorded during the 42-day storage duration. The transcriptomes of peels of fruit treated with propylene for 4 days and those stored at varying temperatures for 28 days were then analyzed by RNA-Seq. We identified three categories of differentially expressed genes that were regulat...

Background Kiwifruit are classified as climacteric since exogenous ethylene (or its analogue prop... more Background Kiwifruit are classified as climacteric since exogenous ethylene (or its analogue propylene) induces rapid ripening accompanied by ethylene production under positive feedback regulation. However, most of the ripening–associated changes (Phase 1 ripening) in kiwifruit during storage and on–vine occur largely in the absence of any detectable ethylene. This ripening behavior is often attributed to basal levels of system I ethylene, although it is suggested to be modulated by low temperature. Results To elucidate the mechanisms regulating Phase 1 ripening in kiwifruit, a comparative transcriptome analysis using fruit continuously exposed to propylene (at 20 °C), and during storage at 5 °C and 20 °C was conducted. Propylene exposure induced kiwifruit softening, reduction of titratable acidity (TA), increase in soluble solids content (SSC) and ethylene production within 5 days. During storage, softening and reduction of TA occurred faster in fruit at 5 °C compared to 20 °C alth...

Kiwifruit gene–specific primers used for Reverse Transcriptase–Quantitative PCR. Accession number... more Kiwifruit gene–specific primers used for Reverse Transcriptase–Quantitative PCR. Accession numbers show genes sourced from the Kiwifruit Genome and NCBI Databases. Homolog genes are indicated in brackets. (XLSX 30 kb)

Selected ripening–associated genes that were differentially regulated either by ethylene or low t... more Selected ripening–associated genes that were differentially regulated either by ethylene or low temperature in 'Sanuki Gold' kiwifruit. (XLSX 33 kb)

Genes that showed antagonistic expression patterns (either up–regulated by propylene but down–reg... more Genes that showed antagonistic expression patterns (either up–regulated by propylene but down–regulated by low temperature, or up–regulated by low temperature but down–regulated by propylene). Values for Harvest, Propylene, 20°CW4 and 5°CW4 indicate average RPKM of 3 independent biological replicates. Orange and blue color shading indicate genes that were up–regulated and down–regulated, respectively. (XLSX 157 kb)

Genes that were regulated by either propylene or low temperature. Values for Harvest, Propylene, ... more Genes that were regulated by either propylene or low temperature. Values for Harvest, Propylene, 20°CW4 and 5°CW4 indicate average RPKM of 3 independent biological replicates. Orange and blue color shading indicate genes that were up–regulated and down–regulated, respectively. (XLSX 179 kb)

Genes that were exclusively regulated by low temperature. Values for Harvest, Propylene, 20°CW4 a... more Genes that were exclusively regulated by low temperature. Values for Harvest, Propylene, 20°CW4 and 5°CW4 indicate average RPKM 3 independent biological replicates. Orange and blue color shading indicate genes that were up–regulated and down–regulated, respectively. (XLSX 198 kb)

Genes that were exclusively regulated by propylene. Values for Harvest, Propylene, 20°CW4 and 5°C... more Genes that were exclusively regulated by propylene. Values for Harvest, Propylene, 20°CW4 and 5°CW4 indicate average RPKM of 3 independent biological replicates. Orange and blue color shading indicate genes that were up–regulated and down–regulated, respectively. (XLSX 378 kb)

Changes in fruit ripening characteristics of 'Rainbow Red' and 'Hayward' during s... more Changes in fruit ripening characteristics of 'Rainbow Red' and 'Hayward' during storage at 20 °C and 5 °C with or without a 1–MCP treatment. Kiwifruit were harvested at commercial maturity and stored in containers, individually separated by about 10 cm. 1–MCP was applied twice a week at 5 μL L− 1 for 12 h. Flesh firmness (A), titratable acidity (B) and soluble solids content (C) were determined periodically using five independent biological replicates. Error bars represent SE. Different letters indicate significant differences at p

Journal of Experimental Botany, 2012

Fruit ripening in response to treatments with propylene, 1-methycyclopropene (1-MCP), and low tem... more Fruit ripening in response to treatments with propylene, 1-methycyclopropene (1-MCP), and low temperature was characterized in 'Sanuki Gold' kiwifruit, Actinidia chinensis Planch. Propylene treatment immediately induced rapid fruit softening, increased AC-PG (polygalacturonase) and AC-EXP (expansin) mRNA accumulation, and stimulated an increase in the soluble solid concentration (SSC) and a decrease in titratable acidity (TA). After 3 d exposure to propylene, ethylene production and AC-PL (pectate lyase) mRNA accumulation were observed. 1-MCP treatment after 24 h exposure to propylene eliminated AC-PG mRNA accumulation and suppressed continued changes in SSC and TA. Application of 1-MCP at the start of the treatment, followed by continuous propylene exposure, markedly delayed fruit softening, and the expression of the cell wall-modifying genes, and changes in the SSC and TA, indicating that kiwifruit become insensitive to ethylene at least for 3 d following 1-MCP exposure. Surprisingly, significant fruit softening, mRNA accumulation of AC-PG, AC-PL, and AC-EXP, and decreased TA were observed without ethylene production in intact fruit stored at low temperature for 1 month, but not in fruit stored at room temperature. Repeated 1-MCP treatments (twice a week) failed to inhibit the changes that occurred in low temperature storage. These observations indicate that low temperature modulates the ripening of kiwifruit in an ethylene-independent manner, suggesting that kiwifruit ripening is inducible by either ethylene or low temperature signals.

Journal of the Japanese Society for Horticultural Science, 2011

The effects of modified atmosphere (MA) storage and application of 1-methylcyclopropene (1-MCP) a... more The effects of modified atmosphere (MA) storage and application of 1-methylcyclopropene (1-MCP) at harvest on the storability and quality of 'Sanuki Gold' kiwifruit harvested at two different maturity stages were investigated. MA storage in both fruit harvested early at 136 days after pollination (DAP) or late at 154 DAP delayed flesh softening, increase in soluble solid concentrations (SSC), decrease in titratable acids (TA), and reduction in fruit flesh color index compared to air stored fruit, suggesting that MA storage is effective in prolonging 'Sanuki Gold' kiwifruit storage life. Further, MA stored fruit did not attain full ripening flesh firmness and SSC thresholds even after 4 months of storage under MA conditions, suggesting that early harvested 'Sanuki Gold' kiwifruit can be stored for 4 months in MA. Fruit from both harvesting maturity stages stored under air conditions achieved maximum SSC (18%) values during storage, suggesting that two weeks early harvesting did not compromise edible quality characteristics. Only late harvested fruit treated with 1-MCP and stored in MA showed slight inhibitory effect specific to fruit softening during the first and second month of storage, suggesting that 1-MCP may have some limited ripening inhibitory effect during storage of 'Sanuki Gold' kiwifruit.

of Thesis 研究科 School Graduate School of Environmental and Life Science 専攻 Division Division of A... more of Thesis 研究科 School Graduate School of Environmental and Life Science 専攻 Division Division of Agricultural and Life Science 学生番号 Student No. 77425801 氏名 Name WILLIAM OLUBERO ASICHE 学位論文題目 Title of Thesis(学位論文題目が英語の場合は和訳を付記) Elucidating physiological and molecular mechanisms of ethylene induced ripening and low temperature modulated ripening

Acta Horticulturae, 2018

Kiwifruit is considered a climacteric fruit since exogenous ethylene induces ripening-associated ... more Kiwifruit is considered a climacteric fruit since exogenous ethylene induces ripening-associated changes. However, we previously reported that low temperature modulated ripening in kiwifruit since ripening occurred faster during storage at 5°C compared to 20°C, in the absence of any detectable ethylene. It is therefore not clear which temperature is suitable for long-term storage of kiwifruit. The purpose of this study was to determine the optimum temperature for long-term storage, and analysis of ripening-related genes in 'Rainbow Red' kiwifruit. Kiwifruit were harvested at commercial maturity, and stored at either 0, 2, 5 or 22°C in ethylene-free chambers. During storage, incidence of fruit deterioration and changes in fruit firmness, soluble solids concentration (SSC) and titratable acidity (TA) were monitored at 4-week intervals. Real-time PCR was also conducted to analyze the changes in expression of selected ripening-related genes. Incidence of fruit fast senescence an...

Kiwifruit is classified as climacteric fruit as exogenous ethylene induces fruit ripening. Howeve... more Kiwifruit is classified as climacteric fruit as exogenous ethylene induces fruit ripening. However, we recently found that ‘Sanuki Gold’ (SG) fruit stored at low temperature (5°C) ripened faster than fruit at room temperature (22°C) unless ethylene was induced by disease development. Some ripening related genes were stimulated at 5°C but not at 22°C. In order to know whether low temperature ripening is common in kiwifruit or not, and to understand temperature response in detail, early-maturing cultivar ‘Rainbow Red’ (RR), SG and late-maturing cultivar ‘Hayward’ (HW) at commercial maturity were stored at 5, 10, 15 or 22°C with or without 1-MCP treatment for 8 weeks. Fruit producing ethylene were eliminated from the experiment. Another group of fruit were treated with propylene (5000ppm) and used as ethylene-ripening fruit. Expression of several ripening-associated genes was compared in fruit stored at various temperatures and fruit treated with propylene. Ethylene biosynthesis genes,...

Postharvest Biology and Technology

Abstract Kiwifruit exhibit a peculiar ripening pattern, as extensive softening is known to occur ... more Abstract Kiwifruit exhibit a peculiar ripening pattern, as extensive softening is known to occur in the absence of any detectable ethylene. We previously demonstrated that this softening is regulated by low temperature independent of ethylene. However, there are no reports that provide comparisons of the ripening patterns among different kiwifruit cultivars at various storage temperatures. The purpose of this study was to compare the ripening responses and associated gene expression in ‘Sanuki Gold’ (Actinidia chinensis var. chinensis) and ‘Hayward’ ((Actinidia chinensis var. deliciosa) fruit, two kiwifruit cultivars differing in on–vine maturity dates and postharvest storability, during storage at 5 °C, 10 °C, 15 °C and 22 °C. Fruit softening, soluble solids concentration (SSC) increase and reduction of titratable acidity (TA) occurred in the absence of any detectable ethylene, and treatment with an ethylene inhibitor 1–methylcyclopropene (1–MCP) failed to suppress the changes, suggesting that they were independent of ethylene. ‘Sanuki Gold’ fruit showed a higher sensitivity to low temperature supported by accelerated fruit softening and TA reduction, and induction of several genes such as AcACO3, AcXET2, AcPG, AcEXP1, AcPMEi, AcGA2ox1, AcMADS2, AcNAC5 and AcbZIP2 at 5 °C, 10 °C and 15 °C within 28 d. By contrast, ‘Hayward’ fruit exhibited a lower sensitivity to low temperature as accelerated softening, TA reduction and induction of most ripening–associated genes were recorded only at 5 °C and 10 °C. These differences in sensitivity to low temperature, between ‘Sanuki Gold’ and ‘Hayward’ fruit, would account for the dissimilarities observed in on–vine maturity dates and postharvest storability.

Frontiers in Plant Science

Journal of Experimental Botany, 2012

Journal of the Japanese Society for Horticultural Science, 2011

Acta Horticulturae, 2018

Postharvest Biology and Technology