Differential regulation of transcript accumulation and alternative splicing of a DREB2 homolog under abiotic stress conditions in common wheat

A number of cold responsive (Cor)/late embryogenesis abundant (Lea) genes are induced by both low temperature (LT) and dehydration. To understand the molecular basis of cold acclimation and its relationship with drought stress response in wheat seedlings, we isolated a DREB2 homolog Wdreb2, which is the candidate gene for a transcription factor of the Cor/Lea genes. The Wdreb2 expression was activated by cold, drought, salt and exogenous ABA treatment. Detailed expression studies of Wdreb2 indicated the involvement of two distinct pathways of its activation, a drought and salt stress-responsive pathway and a cold-responsive pathway. The transient expression analysis showed that the Wrab19 expression was directly activated by the WDREB2 transcription factor in wheat cells. Three transcript forms of Wdreb2 (Wdreb2 alpha, Wdreb2 beta and Wdreb2 gamma) were produced through alternative splicing. Under drought and salt stress conditions, the amount of the Wdreb2 beta form remained fairly constant during 24-hour treatment, while those of the Wdreb2 alpha and Wdreb2 gamma forms showed transient increases. On the other hand, the LT treatment resulted in increased transcript levels of all three forms of Wdreb2. Thus, under the LT and drought/salt stress conditions the amount of the WDREB2 transcription factors in wheat is differentially controlled by the level of transcription and alternative splicing.