ZmCOI6.1, a novel, alternatively spliced maize gene, whose transcript level changes under abiotic stress

Maize (Zea mays L.) is an important crop that is poorly adapted to cold stress; very little is known about the components of the response to stress. By means of the cDNA subtraction technique, several novel genes, responsive to cold stress, have been identified, including ZmCOI6.1, the function of which is unknown. The predicted ZmCOI6.1 amino acid sequence and its homologue are very similar to proteins in rice and Arabidopsis, suggesting that it belongs to a conserved group of plant proteins. Analysis of the ZmCOI6.1 promoter sequence revealed several conserved stress-responsive cis-acting elements. Further characterization of expression showed that ZmCOI6.1 was induced not only by cold, but also by drought and salinity as well as by the signaling molecules abscisic acid and salicylic acid, indicating that ZmCOI6.1 is a stress-responsive gene. ZmCOI6.1 is alternatively spliced and yields two transcripts, the level of which change depending on the stress, indicating a possible mechanism of regulation at the splicing level. Constitutive expression of ZmCOI6.1 in Arabidopsis yielded plants that were less tolerant to abiotic stress, providing evidence that ZmCOI6.1 may be a negative regulator.