GENETIC AND EXPRESSION PROFILING IN SUGARCANE

Commercial varieties of sugarcane accumulate up to 50-60% of the dry weight of stem tissues as sucrose. The accumulation of sucrose occurs in a developmentally programmed tissue-specific manner with a sharp transition from active growth and elongation to sucrose storage functions occurring over a few internodes. We are interested in identifying and characterising the genes that determine the development and function of the sucrose accumulating tissues. Eventually, this may facilitate the manipulation of sugarcane and other plants for enhanced sugar concentration. A dataset of 8504 ESTs has been obtained from two cDNA libraries, one derived from immature stems (YCS-1085 sequences) and one from maturing stems (MCS-7419 sequences) of the sugarcane cultivar Q117. In the YCS library, 59.4% of sequences are homologous to genes of known function, 19.4% are homologous to anonymous genes and 21.0% have no known homologue. In the MCS library, 50.5% are homologous to genes of known function, 26.5% are homologous to anonymous genes and 23.0% have no known homologue. Expression profiles are being performed on a non-redundant set of ESTs and attempts are being made to correlate expression with the onset of sucrose accumulation and with genotypic variation. ESTs of interest and other relevant markers are currently being mapped in both sugarcane and sorghum populations segregating for levels of sucrose accumulation and other traits of interest.