Changes in photosynthetic rates and gene expression of leaves during a source-sink perturbation in sugarcane

A.J. Mccormick, Michael Cramer, D.A. Watt

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    Abstract

    Background and Aims In crops other than sugarcane there is good evidence that the size and activity of carbon sinks influence source activity via sugar-related regulation of the enzymes of photosynthesis, an effect that is partly mediated through coarse regulation of gene expression. Methods In the current study, leaf shading treatments were used to perturb the source–sink balance in 12-month-old Saccharum spp. hybrid ‘N19’ (N19) by restricting source activity to a single mature leaf. Changes in leaf photosynthetic gas exchange variables and leaf and culm sugar concentrations were subsequently measured over a 14 d period. In addition, the changes in leaf gene response to the source–sink perturbation were measured by reverse northern hybridization analysis of an array of 128 expressed sequence tags (ESTs) related to photosynthetic and carbohydrate metabolism. Key Results Sucrose concentrations in immature culm tissue declined significantly over the duration of the shading treatment, while a 57 and 88% increase in the assimilation rate (A) and electron transport rate (ETR), respectively, was observed in the source leaf. Several genes (27) in the leaf displayed a >2-fold change in expression level, including the upregulation of several genes associated with C4 photosynthesis, mitochondrial metabolism and sugar transport. Changes in gene expression levels of several genes, including Rubisco (EC 4·1·1·39) and hexokinase (HXK; EC 2·7·1·1), correlated with changes in photosynthesis and tissue sugar concentrations that occurred subsequent to the source–sink perturbation. Conclusions These results are consistent with the notion that sink demand may limit source activity through a kinase-mediated sugar signalling mechanism that correlates to a decrease in source hexose concentrations, which, in turn, correlate with increased expression of genes involved in photosynthesis and metabolite transport. The signal feedback system reporting sink sufficiency and regulating source activity may be a potentially valuable target for future genetic manipulation to increase sugarcane sucrose yield.
    Original languageEnglish
    Pages (from-to)89-102
    JournalAnnals of Botany
    Volume101
    Issue number1
    DOIs
    Publication statusPublished - 2008

    Fingerprint

    sugarcane
    gene expression
    sugars
    leaves
    photosynthesis
    shade
    genes
    sucrose
    C4 photosynthesis
    hexokinase
    Saccharum
    gene expression regulation
    hexoses
    ribulose-bisphosphate carboxylase
    carbohydrate metabolism
    expressed sequence tags
    genetic engineering
    carbon sinks
    Northern blotting
    electron transfer

    Cite this

    Mccormick, A.J. ; Cramer, Michael ; Watt, D.A. / Changes in photosynthetic rates and gene expression of leaves during a source-sink perturbation in sugarcane. In: Annals of Botany. 2008 ; Vol. 101, No. 1. pp. 89-102.
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    title = "Changes in photosynthetic rates and gene expression of leaves during a source-sink perturbation in sugarcane",
    abstract = "Background and Aims In crops other than sugarcane there is good evidence that the size and activity of carbon sinks influence source activity via sugar-related regulation of the enzymes of photosynthesis, an effect that is partly mediated through coarse regulation of gene expression. Methods In the current study, leaf shading treatments were used to perturb the source–sink balance in 12-month-old Saccharum spp. hybrid ‘N19’ (N19) by restricting source activity to a single mature leaf. Changes in leaf photosynthetic gas exchange variables and leaf and culm sugar concentrations were subsequently measured over a 14 d period. In addition, the changes in leaf gene response to the source–sink perturbation were measured by reverse northern hybridization analysis of an array of 128 expressed sequence tags (ESTs) related to photosynthetic and carbohydrate metabolism. Key Results Sucrose concentrations in immature culm tissue declined significantly over the duration of the shading treatment, while a 57 and 88{\%} increase in the assimilation rate (A) and electron transport rate (ETR), respectively, was observed in the source leaf. Several genes (27) in the leaf displayed a >2-fold change in expression level, including the upregulation of several genes associated with C4 photosynthesis, mitochondrial metabolism and sugar transport. Changes in gene expression levels of several genes, including Rubisco (EC 4·1·1·39) and hexokinase (HXK; EC 2·7·1·1), correlated with changes in photosynthesis and tissue sugar concentrations that occurred subsequent to the source–sink perturbation. Conclusions These results are consistent with the notion that sink demand may limit source activity through a kinase-mediated sugar signalling mechanism that correlates to a decrease in source hexose concentrations, which, in turn, correlate with increased expression of genes involved in photosynthesis and metabolite transport. The signal feedback system reporting sink sufficiency and regulating source activity may be a potentially valuable target for future genetic manipulation to increase sugarcane sucrose yield.",
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    Changes in photosynthetic rates and gene expression of leaves during a source-sink perturbation in sugarcane. / Mccormick, A.J.; Cramer, Michael; Watt, D.A.

    In: Annals of Botany, Vol. 101, No. 1, 2008, p. 89-102.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Changes in photosynthetic rates and gene expression of leaves during a source-sink perturbation in sugarcane

    AU - Mccormick, A.J.

    AU - Cramer, Michael

    AU - Watt, D.A.

    PY - 2008

    Y1 - 2008

    N2 - Background and Aims In crops other than sugarcane there is good evidence that the size and activity of carbon sinks influence source activity via sugar-related regulation of the enzymes of photosynthesis, an effect that is partly mediated through coarse regulation of gene expression. Methods In the current study, leaf shading treatments were used to perturb the source–sink balance in 12-month-old Saccharum spp. hybrid ‘N19’ (N19) by restricting source activity to a single mature leaf. Changes in leaf photosynthetic gas exchange variables and leaf and culm sugar concentrations were subsequently measured over a 14 d period. In addition, the changes in leaf gene response to the source–sink perturbation were measured by reverse northern hybridization analysis of an array of 128 expressed sequence tags (ESTs) related to photosynthetic and carbohydrate metabolism. Key Results Sucrose concentrations in immature culm tissue declined significantly over the duration of the shading treatment, while a 57 and 88% increase in the assimilation rate (A) and electron transport rate (ETR), respectively, was observed in the source leaf. Several genes (27) in the leaf displayed a >2-fold change in expression level, including the upregulation of several genes associated with C4 photosynthesis, mitochondrial metabolism and sugar transport. Changes in gene expression levels of several genes, including Rubisco (EC 4·1·1·39) and hexokinase (HXK; EC 2·7·1·1), correlated with changes in photosynthesis and tissue sugar concentrations that occurred subsequent to the source–sink perturbation. Conclusions These results are consistent with the notion that sink demand may limit source activity through a kinase-mediated sugar signalling mechanism that correlates to a decrease in source hexose concentrations, which, in turn, correlate with increased expression of genes involved in photosynthesis and metabolite transport. The signal feedback system reporting sink sufficiency and regulating source activity may be a potentially valuable target for future genetic manipulation to increase sugarcane sucrose yield.

    AB - Background and Aims In crops other than sugarcane there is good evidence that the size and activity of carbon sinks influence source activity via sugar-related regulation of the enzymes of photosynthesis, an effect that is partly mediated through coarse regulation of gene expression. Methods In the current study, leaf shading treatments were used to perturb the source–sink balance in 12-month-old Saccharum spp. hybrid ‘N19’ (N19) by restricting source activity to a single mature leaf. Changes in leaf photosynthetic gas exchange variables and leaf and culm sugar concentrations were subsequently measured over a 14 d period. In addition, the changes in leaf gene response to the source–sink perturbation were measured by reverse northern hybridization analysis of an array of 128 expressed sequence tags (ESTs) related to photosynthetic and carbohydrate metabolism. Key Results Sucrose concentrations in immature culm tissue declined significantly over the duration of the shading treatment, while a 57 and 88% increase in the assimilation rate (A) and electron transport rate (ETR), respectively, was observed in the source leaf. Several genes (27) in the leaf displayed a >2-fold change in expression level, including the upregulation of several genes associated with C4 photosynthesis, mitochondrial metabolism and sugar transport. Changes in gene expression levels of several genes, including Rubisco (EC 4·1·1·39) and hexokinase (HXK; EC 2·7·1·1), correlated with changes in photosynthesis and tissue sugar concentrations that occurred subsequent to the source–sink perturbation. Conclusions These results are consistent with the notion that sink demand may limit source activity through a kinase-mediated sugar signalling mechanism that correlates to a decrease in source hexose concentrations, which, in turn, correlate with increased expression of genes involved in photosynthesis and metabolite transport. The signal feedback system reporting sink sufficiency and regulating source activity may be a potentially valuable target for future genetic manipulation to increase sugarcane sucrose yield.

    U2 - 10.1093/aob/mcm258

    DO - 10.1093/aob/mcm258

    M3 - Article

    VL - 101

    SP - 89

    EP - 102

    JO - Annals of Botany

    JF - Annals of Botany

    SN - 0305-7364

    IS - 1

    ER -