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Expression Profile of Signal Transduction Components in a Sugarcane Population Segregated for Sugar Content

ABSTRACT: Sucrose is the major product of photosynthesis in many higher plants. It is transported from the source tissue through the phloem to various sink tissues to support plant growth, development and reproduction. Knowledge of the signal transduction pathways involved in carbohydrate metabolism is limited. Genes involved in the regulation of sucrose synthesis and accumulation could be used as tools in the development of genetically manipulated plants with higher sucrose content or aid in breeding programs as molecular markers. Using the SUCEST (Sugarcane EST) database information and a microarray approach, the expression profiles of 1920 sugarcane (Saccharum spp.) genes encoding signal transduction elements, transcription factors and stress-related proteins were analyzed. In order to assess their involvement in sucrose metabolism, the expression profiles of individuals from a sugarcane population segregated for sugar content were compared. From a population of 500 F1 individuals, the seven with the highest and the seven with the lowest sugar contents were selected, pooled and profiled using cDNA microarrays. Twenty-four genes were identified as differentially expressed. Five of them were more expressed in the plants with the highest sugar contents and 19 in the plants with the lowest sugar contents. RNA-blot hybridization was used to validate the expression profiles obtained for individuals in each group. These genes were shown to have differential expression throughout the growing season and in the different tissues. Our data supports the view that sugar levels modulate a complex signal transduction network that seems to involve responses related to stress. Keywords: Segregated population

ORGANISM(S): Saccharum officinarum

PROVIDER: GSE4233 | GEO | 2006/02/14

SECONDARY ACCESSION(S): PRJNA94887

REPOSITORIES: GEO

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Project description:Sugarcane is an economically important crop contributing to the world’s sugar and ethanol production with 80% and 40%, respectively. In recent years, the growing demands for sugar and ethanol production has prompted the necessity to increase sugarcane productivity through conventional breeding programs. However, sugarcane breeders have encountered several difficulties to raise productivity, mainly due to its complex genetics. Sugarcane has a polyploidy genome, with many varieties being aneuploidy. Today, the majority of the planted sugarcane cultivars are complex hybrids derived mainly from crosses between Saccharum officinarum and S. spontaneum. Therefore, proteomics can provide some insight into deciphering gene regulation and changes in carbon metabolism and sucrose accumulation in the culms at different stages of plant development. The aim of this work was to compare the quantitative changes of proteins in sugarcane culms, during plant growth and sucrose accumulation. Total proteins were isolated from both, juvenile and maturing internodes at three stages of plant development. Label free shotgun proteomics was used for protein profiling and quantification. The internodes 5 (I5) and 9 (I9) of 4, 7 and 10 month-old-plants (4M, 7M and 10M, respectively) were harvested and used for proteomic analyses. To mimic field conditions of sucrose accumulation during sugarcane maturation, we stopped watering 10M plants for 10 days. An average of 1130 proteins, unique and differentially expressed across all ages were identified and quantified. Proteins were categorized within 27 functional groups, related to biological process. The patterns of expression for some categories, such as cellular amino acids, metabolic processes, secondary metabolic processes and translation were down-regulated in the immature internode (I5-10M), while up-regulated in the mature I9-10M. We observed an increase in the abundance of several enzymes of the glycolytic pathway and isoforms of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC), in the juvenile stages of development of I9. These changes in enzymes contents indicates that at the early stages of internode development, hypoxia is increasing the glycolytic and ethanolic fermentation pathways, in order to supply ATP for plant growth and NAD+ for mitochondrial respiration, which might be impaired by the low oxygen availability inside the culm.

Project description:Sugarcane accumulates high concentrations of sucrose in the mature stalk, with numerous physiological processes in maturing stalk tissue both directly and indirectly involved. A considerable portion of carbohydrate metabolism is also devoted to cell wall synthesis and fibre production. Previously, we have identified differentially expressed transcripts correlated with sucrose accumulation and fibre production in various internodes of the sugarcane stalk. In this study, we have examined tissue-specific expression patterns to further explore gene pathways responsible for sucrose accumulation and fibre synthesis. We performed large-scale expression profiling of storage parenchyma, vascular bundles and rind dissected from a maturing stalk internode from field-grown commercial sugarcane harvested at 11 months of age. We identified 10 cellulose synthase subunit genes in sugarcane and examined significant differences in the expression of their corresponding transcripts and those of several sugar transporters between the different tissues. These were further correlated with differential expression patterns for transcripts of specific COBRA-like proteins and other proteins with acknowledged roles in cell wall metabolism. We found that the sugar transporters ShPST2a, ShPST2b and ShSUT4 were significantly up-regulated in storage parenchyma while ShSUT1 was up-regulated in vascular bundles. Two co-ordinately expressed groups of cell wall related transcripts were also identified. One group which is associated with primary cell wall synthesis (ShCesA1, ShCesA7, ShCesA9 and Shbk2l3) was up-regulated in parenchyma. The other group which is associated with secondary cell wall synthesis (ShCesA10, ShCesA11, ShCesA12 and Shbk-2) was up-regulated in rind. We also report an unexpected paucity in differential expression of cell wall-related genes in vascular bundles. Our results indicate that there is spatial separation for elevated expression of these important targets in both sucrose accumulation and cell wall synthesis, allowing for increased clarity in our understanding of sucrose transport and fibre synthesis in sugarcane.

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Expression Profile of Signal Transduction Components in a Sugarcane Population Segregated for Sugar Content

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