Differential gene expression in sugarcane leaf and internodal tissues of varying maturity

The expression patterns of sugarcane (Saccharum spp. hybrids) genes were examined in different tissue sources and at developmental stages by 'reverse Northern' hybridisation analysis to identify differentially expressed genes. cDNA arrays containing 1 000 random clones from an immature leaf and maturing culm cDNA library were hybridised with radioactively-labeled poly (A) RNA from immature leaf, mature leaf, immature culm and maturing culm. All cDNAs were found to hybridise to all four probes, but differences in signal intensity were, observed for individual cDNAs between hybridisation events. No cDNAs displaying tissue- or developmental-stage specific expression were detected. Comparisons between hybridisation patterns identified 61 cDNAs that were more abundantly expressed in immature and mature leaf than the culm. Likewise, 25 cDNAs preferentially expressed in immature and maturing culm were detected. ESTs established for the differentially expressed cDNAs revealed sequence homology to a diverse collection of genes in both the leaf and the culm. These included genes associated with general cellular metabolism, transport, regulation and a variety of stress responses. None of the differentially expressed genes identified in the culm were homologous to genes known to be associated with sucrose accumulation. These, preliminary gene expression profiling results suggest that the genetic regulation of processes related to sugarcane leaf and culm maturation is very complex.