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Abstract

The ability of sugarcane to accumulate sucrose provides an experimental system for the study of gene expression determining carbohydrate partitioning and metabolism. A sequence survey of 7242 ESTs derived from the sucrose-accumulating, maturing stem revealed that transcripts for carbohydrate metabolism gene sequences (CMGs) are relatively rare in this tissue. However, within the CMG group, putative sugar transporter ESTs form one of the most abundant classes observed. A combination of EST analysis and microarray and northern hybridization revealed that one of the putative sugar transporter types, designated PST type 2a, was the most abundant and most strongly differentially expressed CMG in maturing stem tissue. PST type 2a is homologous to members of the major facilitator super-family of transporters, possessing 12 predicted transmembrane domains and a sugar transport conserved domain, interrupted by a large cytoplasmic loop. Its transcript was localized to phloem companion cells and associated parenchyma in maturing stem, suggesting a role in sugar translocation rather than storage. In addition, other categories of CMGs show evidence of coordinated expression, such as enzymes involved in sucrose synthesis and cleavage, and a majority of enzymes involved in glycolysis and the pentose phosphate pathway. This study demonstrates the utility of genomic approaches using large-scale EST acquisition and microarray hybridization techniques for studies of the developmental regulation of metabolic enzymes and potential transporters in sugarcane.

De Novo Assembly and Transcriptome Analysis of Contrasting Sugarcane Varieties

“…Transcriptome studies in sugarcane began in South Africa [15], [16], and the largest EST collection (∼238,000 ESTs) was developed through the Brazilian SUCEST project [17], [18]. Researchers in Australia [19]–[21] and the USA [22] have generated three additional libraries containing 10,000 ESTs each. Currently, all of the reported ESTs are collected in the Sugarcane Gene Index, version 3.0, which contains 282,683 ESTs and 499 complete cDNA sequences, resulting in 121,342 unique assembled sequences, or unigenes.…”

Identification of drought-response genes and a study of their expression during sucrose accumulation and water deficit in sugarcane culms

“…Previously, numerous genes with various functions were identified as being differentially expressed between immature culm tissue with low sucrose content and mature culm tissue with high sucrose content through analyses of expressed sequence tags (ESTs) [5] and microarray-derived expression data [6,7]. Transcripts associated with protein synthesis and primary metabolism were more abundant in immature culms, while transcripts corresponding to genes associated with fibre biosynthesis and abiotic stress tolerance, particularly osmotic and oxidative stress, were more abundant in maturing culms [7].…”

“…Transcripts associated with protein synthesis and primary metabolism were more abundant in immature culms, while transcripts corresponding to genes associated with fibre biosynthesis and abiotic stress tolerance, particularly osmotic and oxidative stress, were more abundant in maturing culms [7]. However, genes encoding proteins with known functions related to sucrose metabolism were not highly expressed in culm tissues irrespective of sucrose content [6]. Casu et al [8] proposed that sucrose accumulation may be regulated by a network of genes induced during culm maturation which included clusters of genes with roles that contribute to key physiological processes including sugar translocation and transport, fibre synthesis, membrane transport, vacuole development and function, and abiotic stress tolerance.…”

The choice of reference genes for assessing gene expression in sugarcane under salinity and drought stresses

“…Traditional breeding strategy for resistance improvement is lagging behind the demand of commercial need for lack of knowledge about stress tolerance-related traits, lack of efficient selection techniques, and low of genetic variance and fertility6. Recently, subtractive hybridization78, cDNA microarray910, transcript expression profile11, proteome12, transcriptome13 and microRNA-seq14, known as differential display and serial analysis of gene expression techniques and strategies, have been used to identify genes and molecular markers involved in stress responses, and the following genetic modifications with these genes or application of these markers would be an enormous advantage for improvement of breeding15. The previously researches showed that such a large number of genes with minor gene effects regulate water deficiency-mediated stress tolerance, which referred to complex quantitative traits that vary in plants616.…”