To investigate the molecular mechanisms of Al toxicity, cross-species cDNA array approach was employed to identify expressed sequence tags (ESTs) regulated by Al stress in root tips of Al-tolerant maize (Zea mays) genotype Cat100-6 and Al-sensitive genotype S1587-17. Due to the high degree of conservation observed between sugarcane and maize, we have analyzed the expression profiling of maize genes using 2 304 sugarcane (ESTs) obtained from different libraries. We have identified 85 ESTs in Al stressed maize root tips with significantly altered expression. Among the up-regulated ESTs, we have found genes encoding previously identified proteins induced by Al stress, such as phenyl ammonia-lyase, chitinase, Bowman-Birk proteinase inhibitor, and wali7. In addition, several novel genes up-and downregulated by Al stress were identified in both genotypes.
The control of gene expression in precise time and space is a desirable attribute of chemically inducible systems. Ethanol is a chemical inducer with favourable features, such as being inexpensive and easy to apply. The aim of this study was to identify ethanol-responsive genes in sugarcane. The cDNA macroarray technique was adopted to identify transcript changes in sugarcane leaves (Saccharum spp. cv SP80-3280) exposed to ethanol. The expression profiles of sugarcane genes were analysed using nylon filters containing 3,575 cDNA clones from the leaf roll library of the SUCEST project. Seventy expressed sequence tags (ESTs) presented altered expression patterns, including ESTs corresponding to genes related to transcriptional and translational processes, abiotic stress and others. Several genes of unknown function were also identified. Among the 48 ESTs up-regulated by ethanol, an abiotic stress-responsive protein and an unknown function gene presented rapid induction by ethanol. The macroarray data of selected ethanol-responsive EST were confirmed by RNA-blot hybridisation. The expression profile of the 48 up-regulated genes was compared in two other cultivars: SP89-1115 and SP90-3414. Surprisingly, no gene showed a similar expression profile in the three cultivars. This result suggests that sugarcane plants have a high diversity in their responses to ethanol.
Stresses such as cold and drought can impair plant yield and induce a highly complex array of responses. Sugarcane (Saccharum spp.) is cultivated in tropical and subtropical areas and is considered a coldsensitive plant. We previously showed that cold stress induces the expression of several genes in in vitro sugarcane plantlets. Here we characterize one of those genes, SsNAC23, a member of the NAC family of plant-specific transcription factors, which are induced by low temperature and other stresses in several plant species. The expression of SsNAC23 was induced in sugarcane plants exposed to low temperatures (4ºC). With the aim of further understanding the regulatory network in response to stress, we used the yeast two-hybrid system to identify sugarcane proteins that interact with SsNAC23. Using SsNAC23 as bait, we screened a cDNA expression library of sugarcane plants submitted to 4ºC for 48 h. Several interacting partners were identified, including stress-related proteins, increasing our knowledge on how sugarcane plants respond to cold stress. One of these interacting partners, a thioredoxin h1, offers insights into the regulation of SsNAC23 activity.
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