Ewald Komor - Academia.edu (original) (raw)

Papers by Ewald Komor

Research paper thumbnail of Sugar-transport by sugarcane vacuoles

Research paper thumbnail of Transport of hexoses depolarizes the membrane potential of Chlorella vulgaris

Research paper thumbnail of Elicitation of phytoalexins: Accumulation and phloem characteristics by some fungi and mycotoxins in Ricinus communis L

Research paper thumbnail of Correlation-Peak Imaging

Journal of Magnetic Resonance, Series B, 1996

Identification and quantitation in conventional 1H spectroscopic imaging in vivo is often hampere... more Identification and quantitation in conventional 1H spectroscopic imaging in vivo is often hampered by the small chemical-shift range. To improve the spectral resolution of spectroscopic imaging, homonuclear two-dimensional correlation spectroscopy has been combined with phase encoding of the spatial dimensions. From the theoretical description of the coherence-transfer signal in the Fourier-transform domain, a comprehensive acquisition and processing strategy is presented that includes optimization of the width and the position of the acquisition windows, matched filtering of the signal envelope, and graphical presentation of the cross peak of interest. The procedure has been applied to image the spatial distribution of the correlation peaks from specific spin systems in the hypocotyl of castor bean (Ricinus communis) seedlings. Despite the overlap of many resonances, correlation-peak imaging made it possible to observe a number of proton resonances, such as those of sucrose, beta-glucose, glutamine/glutamate, lysine, and arginine.

Research paper thumbnail of The Ricinus seedling : a model plant to study phloem transport

Research paper thumbnail of Impact of polyethylene glycol-induced water stress on growth and development of shoot tip cultures from different banana (Musa spp.) cultivars

Journal of Applied Horticulture Lucknow, 2006

Shoot tip explants of the Egyptian banana cultivars Maghraby, Valery, Grand Nain and Hindy were t... more Shoot tip explants of the Egyptian banana cultivars Maghraby, Valery, Grand Nain and Hindy were tested for their tolerance to water stress. Shoot survival, shoot growth and root growth stimulation in presence of polyethylene glycol (PEG) was strongest in cultivar Hindy followed by Grand Nain, Maghraby and Valery. The accumulation of soluble sugars and proline in shoots was positively correlated with the applied polyethylene glycol concentration, while the reverse was true for N, P and K content. The cultivar Hindy exhibited higher metabolite accumulation response and cultivar Maghraby the least. The effects were most clear on liquid medium whereas solid (agar) medium exerted some additional effects increasing the osmotic stress at low PEG concentrations and alleviating the PEG effect at high PEG concentrations. In conclusion, the cultivar Hindy appeared to be the most tolerant to water stress because of strong accumulation of compatible solutes and greater stimulation of root develo...

Research paper thumbnail of Effect of magnesium and ATP on ATPase of sugarcane vacuoles

Planta, 1984

Kinetic analysis of the Mg 2 +-dependence of tonoplast ATPase from suspension-cultured cells of s... more Kinetic analysis of the Mg 2 +-dependence of tonoplast ATPase from suspension-cultured cells of sugarcane showed that the enzyme activity increased with increasing magnesium concentrations till 1-3 mM and then decreased considerably for higher concentrations. This kinetic could be explained by the assumption that MgATP 2-is the substrate of ATPase: MgATP 2-concentration increases with increasing concentration of magnesium till, at high concentrations of magnesium, Mg2ATP is formed. No evidence for a direct role of Mg z + as activator or inhibitor was found. These data corroborate previous findings that MgATP zis the sole substrate of the vacuolar ATPase of sugarcane (Thorn and Komor 1984). High concentrations of ATP seemed to inhibit the ATPase. This result, however, could be traced back to interference of ATP with the Fiske-Subbarow method of phosphate determination. After adjustment of the test conditions, inhibition by ATP was no longer found. Reported data for ATPases of other plant materials, showing inhibition of enzyme activity with high magnesium or ATP concentrations, might be explicable in a similar way.

Research paper thumbnail of pH-Dependent Change in Km Values and Translocation Constants of the Uptake System

The proton concentration in the medium affects the maximal velocity of sugar uptake with a Km of ... more The proton concentration in the medium affects the maximal velocity of sugar uptake with a Km of 0.3 mM (high affinity uptake). By decreasing the proton concentration a decrease in high affinity sugar uptake is observed, in parallel the activity of a low affinity uptake system (K, of 50 mM) rises. Both systems add up to 100 %. The existence of the carrier in two conformational states (protonated and unprotonated) has been proposed therefore, the protonated form with high affinity to 6-deoxyglucose, the unprotonated form with low affinity. A plot of extrapolated V. values at low substrate concentration versus proton concentration results in a Km for protons of 0.14 AiM, i.e. half-maximal protonation of the carrier is achieved at pH 6.85. The stoichiometry of protons cotransported per 6-deoxyglucose is close to 1 at pH 6.0-6.5. At higher pH values the stoichiometry continuously decreases; at pH 8.0 only one proton is cotransported per four molecules of sugar. Whereas the translocation...

Research paper thumbnail of Relationship of sucrose metabolism enzymes with sucrose storage in sugarcane

Research paper thumbnail of Phytoalexins: characteristics, defence mechanism and their elicitation by fungi

Research paper thumbnail of Sucrose proton symport for phloem loading in the Ricinus seedling

Research paper thumbnail of Yellow leaf disease of sugarcane : Geographic distribution, spreading in the field, impact on plant performance and possible counteractions

Research paper thumbnail of Sucrose uptake and sucrose hydrolysis by plant cells : quantitative aspects

Research paper thumbnail of Springtime Bark-Splitting of Acer pseudoplatanus in Germany

Forests

A large-scale regional event of springtime bark-splitting in Acer pseudoplatanus was observed in ... more A large-scale regional event of springtime bark-splitting in Acer pseudoplatanus was observed in Germany in May 2018, where bark dissected from the wood. In young trees, an average of about 30% of the circumference was affected by cracks that were up to 8 m long. The damage occurred on the south-facing side of the trees after a warm period in March, followed by an extreme cold spell and warm temperatures. In this study, we investigated the possible causes of this damage. The damage occurred in the expanding xylem with cambial cells remaining in the bark. These cells-initiated growths of new, bark-based stems. The unprotected xylem was attacked by several fungi and wood-boring bark beetles. The mode of damage-recovery suggested that this event will eventually lead to a frost-scar-like structure in the future that will not totally heal, because the new stems attached to the old bark were in the process of forming new bark. Due to the increase in variation of springtime temperatures ob...

Research paper thumbnail of A non-invasive measurement of phloem and xylem water flow in castor bean seedlings by nuclear magnetic resonance microimaging

Planta

A flow-sensitive nuclear magnetic resonance (NMR) microimaging technique was applied to measure d... more A flow-sensitive nuclear magnetic resonance (NMR) microimaging technique was applied to measure directly the in-vivo water flow in 6-d-old castor bean seedlings. The achieved in-plane resolution of the technique allowed discrimination between xylem and phloem water flow. Both the xylem-and the phloem-average flow velocities in the intact seedling could be quantified. Furthermore, the total conductive cross-sectional area of the xylem vessels and the phloem sieve elements could be determined using the non-invasive and non-destructive NMR microimaging technique. Hence, it was possible to calculate the in-vivo volume flow rates for both xylem and phloem water flow. Our non-destructive technique showed that previously used methods to measure phloem water flow affected the flow rate itself. In the intact seedlings we found values of 16.6 pl-h-1, two fold lower than those previously estimated from phloem exudation rates. Finally, our results demonstrate for the first time that water is internally circulated between phloem and xylem, and that water flow within the xylem is maintained by this internally circulated water, even in the absence of any significant transpiration or evaporation.

Research paper thumbnail of Assessment of sucrose transporters, metabolites and sucrose phosphate synthase in different sugarcane tissues

Physiology and molecular biology of plants : an international journal of functional plant biology, 2017

The expression of sucrose-phosphate synthase II (SPSII) and sucrose transporters ShSUT1A and ShSU... more The expression of sucrose-phosphate synthase II (SPSII) and sucrose transporters ShSUT1A and ShSUT4 were determined by RT-PCR and qRT-PCR in the sink and source leaves and in rind and pith of mature internodes of four high-yielding Hawaiian sugarcane cultivars. Expression of SPSII, ShSUT1A, and ShSUT4 was lower in pith than in rind, except in one cultivar, but else quite similar in the cultivars. The strong expression of transporter ShSUT4 in the rind of the internodes may hint to a special role of ShSUT4 in the rind. ShSUT4-expression in the sink and source leaves was similar in all four cultivars, whereas large differences were found for the expression of ShSUT1A and SPSII between the source and sink leaves and between the cultivars. The levels of sucrose precursors were doubled in source leaves compared to sink leaves, whereas they were higher in immature internode compared to mature internode. The role of sucrose transporters and SPSII in leaves and internodes is discussed, but ...

Research paper thumbnail of Saccharoseferntransport und Saccharosespeicherung

Berichte Der Deutschen Botanischen Gesellschaft, Oct 1, 1984

Les mecanismes du transport du saccharose sont etudies dans les cotyledons de Ricinus communis et... more Les mecanismes du transport du saccharose sont etudies dans les cotyledons de Ricinus communis et la mise en reserve du saccharose est etudiee a l'aide de cultures en suspension des cellules parenchymateuses de Saccharum officinarum

Research paper thumbnail of Transgenic sugarcane with coat protein gene-based silencing shows increased resistance to sugarcane yellow leaf virus (ScYLV)

SUGARCANE yellowleaf syndrome (YLS), caused by Sugarcane yellow leaf virus (ScYLV) is worldwide i... more SUGARCANE yellowleaf syndrome (YLS), caused by Sugarcane yellow leaf virus (ScYLV) is worldwide in distribution where susceptible cultivars are grown. This study was undertaken to produce transgenic sugarcane that is resistant to ScYLV by means of a gene silencing mechanism. Transgenic sugarcane lines were produced by biolistic bombardment with an untranslatable virus coat protein construct. The presence of the transgene was confirmed with PCR and Southern blot analyses. Viral resistance of the transgenic plants was evaluated by inoculation with viruliferous aphid vectors followed by tissue blot immunoassay (TBIA), and inoculation results indicated the resistance levels in transgenic sugarcane were significantly higher than non-transformed controls. The uninfected transgenic plants will be used for studying the effects of the virus on sugar and biomass yield in comparison with infected plants and may provide resistant germplasm for the sugarcane breeding program. Introduction Yellow leaf syndrome (YLS) has been reported on sugarcane worldwide (Borth et al., 1994; Comstock et al., 1994; Moutia and Saumtally, 1999; Rassaby et al., 2003; Vega et al., 1997). In several cases, YLS was associated with substantial yield losses (Rassaby et al., 2003; Vega et al., 1997). Viral particles found in the phloem of leaves with YLS were characterised as those of a luteovirus, named Sugarcane yellowleaf virus (ScYLV) (Vega et al., 1997). Analysis of viral RNAsequences revealed that ScYLV belonged to the Polerovirus group (Maia et al., 2000; Moonan et al., 2000). Antibodies against the purified virus were produced to assay for the presence of the virus in sugarcane tissues (Scagliusi and Lockhart, 2000). Surveys in Hawaii found the virus to be widespread in both YLS and symptomless plants, although no control measures are currently being practised (Schenck et al., 1997; Schenck and Lehrer, 2000). This paper reports that transgenic sugarcane containing an untranslatable ScYLV coat protein gene had increased resistance to ScYLV. Gene silencing seems to be a universal mechanism for plant resistance to viral infection (Baulcombe, 1996) and posttranscriptional gene silencing has already been achieved in sugarcane by transformation with an untranslatable piece of Sorghum Mosaic Virus (Ingelbrecht et al., 1999).

Research paper thumbnail of Carbon dioxide assimilation by virus-free sugarcane plants and by plants which were infected by Sugarcane Yellow Leaf Virus

Physiological and Molecular Plant Pathology, 2008

Infection of sugarcane by Sugarcane Yellow Leaf Virus (SCYLV) remains mostly asymptomatic. The as... more Infection of sugarcane by Sugarcane Yellow Leaf Virus (SCYLV) remains mostly asymptomatic. The assimilation rates and the water relations parameters were measured to test whether the plants are already inflicted by the infection. The assimilation rate and the stomatal conductance were 10-30% higher in virus-free plants than in infected plants. The observed differences were significant in young potted plants, not in older field plants. Virus-free leaves had a higher bundle sheath leakiness and a lower 13 C discrimination rate than infected leaves. The water relations parameters of SCYLV-infected asymptomatic plants showed resemblance to those of salinity-and drought-stressed plants.

Research paper thumbnail of Modulation of carbohydrate metabolism and chloroplast structure in sugarcane leaves which were infected by Sugarcane Yellow Leaf Virus (SCYLV)

Physiological and Molecular Plant Pathology, 2008

Non-symptomatic sugarcane plants infected with Sugarcane Yellow Leaf Virus showed starch in mesop... more Non-symptomatic sugarcane plants infected with Sugarcane Yellow Leaf Virus showed starch in mesophyll and bundle sheath cells. In situ-hybridization of mRNAs of sucrose-phosphate phosphatase and ADPglucose pyrophosphorylase revealed that infected leaves contained SPPase and AGPase in mesophyll cells, Kranz cells and bundle sheath cells. In contrast virus-free leaves contained SPPase only in Kranz cells and AGPase only in bundle sheath cells. Infected leaves exhibited ultrastructural changes in Kranz cell chloroplasts and a shift of the chlorophyll a/b ratio. No obstruction of plasmodesmata was observed. The results indicate that SCYLV-infected plants, even when visually non-symptomatic, underwent strong metabolic and ultrastructural changes.

Research paper thumbnail of Sugar-transport by sugarcane vacuoles

Research paper thumbnail of Transport of hexoses depolarizes the membrane potential of Chlorella vulgaris

Research paper thumbnail of Elicitation of phytoalexins: Accumulation and phloem characteristics by some fungi and mycotoxins in Ricinus communis L

Research paper thumbnail of Correlation-Peak Imaging

Journal of Magnetic Resonance, Series B, 1996

Identification and quantitation in conventional 1H spectroscopic imaging in vivo is often hampere... more Identification and quantitation in conventional 1H spectroscopic imaging in vivo is often hampered by the small chemical-shift range. To improve the spectral resolution of spectroscopic imaging, homonuclear two-dimensional correlation spectroscopy has been combined with phase encoding of the spatial dimensions. From the theoretical description of the coherence-transfer signal in the Fourier-transform domain, a comprehensive acquisition and processing strategy is presented that includes optimization of the width and the position of the acquisition windows, matched filtering of the signal envelope, and graphical presentation of the cross peak of interest. The procedure has been applied to image the spatial distribution of the correlation peaks from specific spin systems in the hypocotyl of castor bean (Ricinus communis) seedlings. Despite the overlap of many resonances, correlation-peak imaging made it possible to observe a number of proton resonances, such as those of sucrose, beta-glucose, glutamine/glutamate, lysine, and arginine.

Research paper thumbnail of The Ricinus seedling : a model plant to study phloem transport

Research paper thumbnail of Impact of polyethylene glycol-induced water stress on growth and development of shoot tip cultures from different banana (Musa spp.) cultivars

Journal of Applied Horticulture Lucknow, 2006

Shoot tip explants of the Egyptian banana cultivars Maghraby, Valery, Grand Nain and Hindy were t... more Shoot tip explants of the Egyptian banana cultivars Maghraby, Valery, Grand Nain and Hindy were tested for their tolerance to water stress. Shoot survival, shoot growth and root growth stimulation in presence of polyethylene glycol (PEG) was strongest in cultivar Hindy followed by Grand Nain, Maghraby and Valery. The accumulation of soluble sugars and proline in shoots was positively correlated with the applied polyethylene glycol concentration, while the reverse was true for N, P and K content. The cultivar Hindy exhibited higher metabolite accumulation response and cultivar Maghraby the least. The effects were most clear on liquid medium whereas solid (agar) medium exerted some additional effects increasing the osmotic stress at low PEG concentrations and alleviating the PEG effect at high PEG concentrations. In conclusion, the cultivar Hindy appeared to be the most tolerant to water stress because of strong accumulation of compatible solutes and greater stimulation of root develo...

Research paper thumbnail of Effect of magnesium and ATP on ATPase of sugarcane vacuoles

Planta, 1984

Kinetic analysis of the Mg 2 +-dependence of tonoplast ATPase from suspension-cultured cells of s... more Kinetic analysis of the Mg 2 +-dependence of tonoplast ATPase from suspension-cultured cells of sugarcane showed that the enzyme activity increased with increasing magnesium concentrations till 1-3 mM and then decreased considerably for higher concentrations. This kinetic could be explained by the assumption that MgATP 2-is the substrate of ATPase: MgATP 2-concentration increases with increasing concentration of magnesium till, at high concentrations of magnesium, Mg2ATP is formed. No evidence for a direct role of Mg z + as activator or inhibitor was found. These data corroborate previous findings that MgATP zis the sole substrate of the vacuolar ATPase of sugarcane (Thorn and Komor 1984). High concentrations of ATP seemed to inhibit the ATPase. This result, however, could be traced back to interference of ATP with the Fiske-Subbarow method of phosphate determination. After adjustment of the test conditions, inhibition by ATP was no longer found. Reported data for ATPases of other plant materials, showing inhibition of enzyme activity with high magnesium or ATP concentrations, might be explicable in a similar way.

Research paper thumbnail of pH-Dependent Change in Km Values and Translocation Constants of the Uptake System

The proton concentration in the medium affects the maximal velocity of sugar uptake with a Km of ... more The proton concentration in the medium affects the maximal velocity of sugar uptake with a Km of 0.3 mM (high affinity uptake). By decreasing the proton concentration a decrease in high affinity sugar uptake is observed, in parallel the activity of a low affinity uptake system (K, of 50 mM) rises. Both systems add up to 100 %. The existence of the carrier in two conformational states (protonated and unprotonated) has been proposed therefore, the protonated form with high affinity to 6-deoxyglucose, the unprotonated form with low affinity. A plot of extrapolated V. values at low substrate concentration versus proton concentration results in a Km for protons of 0.14 AiM, i.e. half-maximal protonation of the carrier is achieved at pH 6.85. The stoichiometry of protons cotransported per 6-deoxyglucose is close to 1 at pH 6.0-6.5. At higher pH values the stoichiometry continuously decreases; at pH 8.0 only one proton is cotransported per four molecules of sugar. Whereas the translocation...

Research paper thumbnail of Relationship of sucrose metabolism enzymes with sucrose storage in sugarcane

Research paper thumbnail of Phytoalexins: characteristics, defence mechanism and their elicitation by fungi

Research paper thumbnail of Sucrose proton symport for phloem loading in the Ricinus seedling

Research paper thumbnail of Yellow leaf disease of sugarcane : Geographic distribution, spreading in the field, impact on plant performance and possible counteractions

Research paper thumbnail of Sucrose uptake and sucrose hydrolysis by plant cells : quantitative aspects

Research paper thumbnail of Springtime Bark-Splitting of Acer pseudoplatanus in Germany

Forests

A large-scale regional event of springtime bark-splitting in Acer pseudoplatanus was observed in ... more A large-scale regional event of springtime bark-splitting in Acer pseudoplatanus was observed in Germany in May 2018, where bark dissected from the wood. In young trees, an average of about 30% of the circumference was affected by cracks that were up to 8 m long. The damage occurred on the south-facing side of the trees after a warm period in March, followed by an extreme cold spell and warm temperatures. In this study, we investigated the possible causes of this damage. The damage occurred in the expanding xylem with cambial cells remaining in the bark. These cells-initiated growths of new, bark-based stems. The unprotected xylem was attacked by several fungi and wood-boring bark beetles. The mode of damage-recovery suggested that this event will eventually lead to a frost-scar-like structure in the future that will not totally heal, because the new stems attached to the old bark were in the process of forming new bark. Due to the increase in variation of springtime temperatures ob...

Research paper thumbnail of A non-invasive measurement of phloem and xylem water flow in castor bean seedlings by nuclear magnetic resonance microimaging

Planta

A flow-sensitive nuclear magnetic resonance (NMR) microimaging technique was applied to measure d... more A flow-sensitive nuclear magnetic resonance (NMR) microimaging technique was applied to measure directly the in-vivo water flow in 6-d-old castor bean seedlings. The achieved in-plane resolution of the technique allowed discrimination between xylem and phloem water flow. Both the xylem-and the phloem-average flow velocities in the intact seedling could be quantified. Furthermore, the total conductive cross-sectional area of the xylem vessels and the phloem sieve elements could be determined using the non-invasive and non-destructive NMR microimaging technique. Hence, it was possible to calculate the in-vivo volume flow rates for both xylem and phloem water flow. Our non-destructive technique showed that previously used methods to measure phloem water flow affected the flow rate itself. In the intact seedlings we found values of 16.6 pl-h-1, two fold lower than those previously estimated from phloem exudation rates. Finally, our results demonstrate for the first time that water is internally circulated between phloem and xylem, and that water flow within the xylem is maintained by this internally circulated water, even in the absence of any significant transpiration or evaporation.

Research paper thumbnail of Assessment of sucrose transporters, metabolites and sucrose phosphate synthase in different sugarcane tissues

Physiology and molecular biology of plants : an international journal of functional plant biology, 2017

The expression of sucrose-phosphate synthase II (SPSII) and sucrose transporters ShSUT1A and ShSU... more The expression of sucrose-phosphate synthase II (SPSII) and sucrose transporters ShSUT1A and ShSUT4 were determined by RT-PCR and qRT-PCR in the sink and source leaves and in rind and pith of mature internodes of four high-yielding Hawaiian sugarcane cultivars. Expression of SPSII, ShSUT1A, and ShSUT4 was lower in pith than in rind, except in one cultivar, but else quite similar in the cultivars. The strong expression of transporter ShSUT4 in the rind of the internodes may hint to a special role of ShSUT4 in the rind. ShSUT4-expression in the sink and source leaves was similar in all four cultivars, whereas large differences were found for the expression of ShSUT1A and SPSII between the source and sink leaves and between the cultivars. The levels of sucrose precursors were doubled in source leaves compared to sink leaves, whereas they were higher in immature internode compared to mature internode. The role of sucrose transporters and SPSII in leaves and internodes is discussed, but ...

Research paper thumbnail of Saccharoseferntransport und Saccharosespeicherung

Berichte Der Deutschen Botanischen Gesellschaft, Oct 1, 1984

Les mecanismes du transport du saccharose sont etudies dans les cotyledons de Ricinus communis et... more Les mecanismes du transport du saccharose sont etudies dans les cotyledons de Ricinus communis et la mise en reserve du saccharose est etudiee a l'aide de cultures en suspension des cellules parenchymateuses de Saccharum officinarum

Research paper thumbnail of Transgenic sugarcane with coat protein gene-based silencing shows increased resistance to sugarcane yellow leaf virus (ScYLV)

SUGARCANE yellowleaf syndrome (YLS), caused by Sugarcane yellow leaf virus (ScYLV) is worldwide i... more SUGARCANE yellowleaf syndrome (YLS), caused by Sugarcane yellow leaf virus (ScYLV) is worldwide in distribution where susceptible cultivars are grown. This study was undertaken to produce transgenic sugarcane that is resistant to ScYLV by means of a gene silencing mechanism. Transgenic sugarcane lines were produced by biolistic bombardment with an untranslatable virus coat protein construct. The presence of the transgene was confirmed with PCR and Southern blot analyses. Viral resistance of the transgenic plants was evaluated by inoculation with viruliferous aphid vectors followed by tissue blot immunoassay (TBIA), and inoculation results indicated the resistance levels in transgenic sugarcane were significantly higher than non-transformed controls. The uninfected transgenic plants will be used for studying the effects of the virus on sugar and biomass yield in comparison with infected plants and may provide resistant germplasm for the sugarcane breeding program. Introduction Yellow leaf syndrome (YLS) has been reported on sugarcane worldwide (Borth et al., 1994; Comstock et al., 1994; Moutia and Saumtally, 1999; Rassaby et al., 2003; Vega et al., 1997). In several cases, YLS was associated with substantial yield losses (Rassaby et al., 2003; Vega et al., 1997). Viral particles found in the phloem of leaves with YLS were characterised as those of a luteovirus, named Sugarcane yellowleaf virus (ScYLV) (Vega et al., 1997). Analysis of viral RNAsequences revealed that ScYLV belonged to the Polerovirus group (Maia et al., 2000; Moonan et al., 2000). Antibodies against the purified virus were produced to assay for the presence of the virus in sugarcane tissues (Scagliusi and Lockhart, 2000). Surveys in Hawaii found the virus to be widespread in both YLS and symptomless plants, although no control measures are currently being practised (Schenck et al., 1997; Schenck and Lehrer, 2000). This paper reports that transgenic sugarcane containing an untranslatable ScYLV coat protein gene had increased resistance to ScYLV. Gene silencing seems to be a universal mechanism for plant resistance to viral infection (Baulcombe, 1996) and posttranscriptional gene silencing has already been achieved in sugarcane by transformation with an untranslatable piece of Sorghum Mosaic Virus (Ingelbrecht et al., 1999).

Research paper thumbnail of Carbon dioxide assimilation by virus-free sugarcane plants and by plants which were infected by Sugarcane Yellow Leaf Virus

Physiological and Molecular Plant Pathology, 2008

Infection of sugarcane by Sugarcane Yellow Leaf Virus (SCYLV) remains mostly asymptomatic. The as... more Infection of sugarcane by Sugarcane Yellow Leaf Virus (SCYLV) remains mostly asymptomatic. The assimilation rates and the water relations parameters were measured to test whether the plants are already inflicted by the infection. The assimilation rate and the stomatal conductance were 10-30% higher in virus-free plants than in infected plants. The observed differences were significant in young potted plants, not in older field plants. Virus-free leaves had a higher bundle sheath leakiness and a lower 13 C discrimination rate than infected leaves. The water relations parameters of SCYLV-infected asymptomatic plants showed resemblance to those of salinity-and drought-stressed plants.

Research paper thumbnail of Modulation of carbohydrate metabolism and chloroplast structure in sugarcane leaves which were infected by Sugarcane Yellow Leaf Virus (SCYLV)

Physiological and Molecular Plant Pathology, 2008

Non-symptomatic sugarcane plants infected with Sugarcane Yellow Leaf Virus showed starch in mesop... more Non-symptomatic sugarcane plants infected with Sugarcane Yellow Leaf Virus showed starch in mesophyll and bundle sheath cells. In situ-hybridization of mRNAs of sucrose-phosphate phosphatase and ADPglucose pyrophosphorylase revealed that infected leaves contained SPPase and AGPase in mesophyll cells, Kranz cells and bundle sheath cells. In contrast virus-free leaves contained SPPase only in Kranz cells and AGPase only in bundle sheath cells. Infected leaves exhibited ultrastructural changes in Kranz cell chloroplasts and a shift of the chlorophyll a/b ratio. No obstruction of plasmodesmata was observed. The results indicate that SCYLV-infected plants, even when visually non-symptomatic, underwent strong metabolic and ultrastructural changes.