Increasing Drought Tolerance Through the Functional Characterization of Cotton ABFs and CBFs

Recent exceptional drought, coupled with high heat, has highlighted the need for the development of cotton varieties that are better able to withstand abiotic stress. Use of transgenic technology to introduce genes that encode regulatory factors that control plant stress responses is an important approach to develop stress tolerant germplasm resources. The majority of genetically altered crops focus on monogenic traits, leading to insecticide and herbicide resistance, however, abiotic stress tolerance is based on complex regulatory networks, making transcription factors, which control the expression of multiple genes, an attractive target.

While there are many gene families involved in the abiotic stress response, the ABA-responsive element binding factors (ABFs) and C-repeat binding factors (CBFs) are of particular interest as they play an important role in drought and temperature response and have been shown to interact to coordinate these responses. Previous studies have shown that the over-expression of these genes in Arabidopsis confers significant abiotic stress tolerance, and heterologous expression of the Arabidopsis ABF3 and CBF3 genes in cotton leads to increased drought tolerance, though with negative reproductive consequences.

Here we characterize the ABF and CBF gene homologs from cotton, detail their expression patterns in response to various abiotic stresses, and describe their promoter regions, in comparison to Arabidopsis. We are also examining the effects of heterologous expression of cotton ABFs and CBFs in Arabidopsis, and hypothesize that endogenous ectopic expression of the ABFs and CBFs in cotton may confer increased abiotic stress tolerance while minimizing the associated negative effects of a heterologous system, based on endogenous post-transcriptional modification.