The CBF1/DREB1C Transcription Factor is a Common Regulator of Hormonal, Biotic and Abiotic Stress Responses in Sugarcane

Stress signaling crosstalk was examined in sugarcane using Affymetrix GeneChips. Coordinated stress responses were monitored in a commercial, drought-susceptible variety (CP72-1210) by characterizing transcript levels of 6,024 ESTs after treatment with (a) salicylic acid (SA), jasmonic acid (JA) or methyl jasmonate (MeJA), or (b) exposure to the pathogen Sorghum mosaic virus (SrMV). Some genes that were co-induced by SA, JA and MeJA, were down-regulated upon SrMV infection. Most significantly, co-induction included genes associated with: oxidative burst hypersensitive responses, defense mechanisms, and drought response. One group comprised genes that encode proteins involved in regulating signal transduction: transcription factors, protein kinases and protein phosphatases. Another group comprised genes that encode downstream products such as channel proteins, osmotin, dehydrin and late embryogenesis abundant proteins. Transcription factor families common to the coordinated responses included: CBF/DREB, MYB/MYC, AP2/ERF and bZIP/AREB. These findings indicate significant coordination in defense signaling and suggest crosstalk between responses to biotic and abiotic stress. The cDNAs encoding CBF1/DREB1C (SsCBF1) and CBF3/DREB1D were isolated from mixed sugarcane tissues treated with cold, drought and salinity and constitutively expressed in several drought susceptible varieties. Lines overexpressing SsCBF1 have shown enhanced tolerance to abiotic stress with up to 60% survival after 5 days at 10^o C, 80% survival at 0.4 M salt, and 90% survival after drought exposure for three weeks. These findings will aid the development of varieties that are better suited to marginal environments.