Less is more against drought in wheat

Mei, Chen, Mao and colleagues harness the power of GWAS to identify gain-of-function allele of TaDTG6-B, which directly activates TaPIF1 transcription and ameliorates drought tolerance. https://doi.org/10.1093/plcell/koac248

Background: Wheat (Triticum aestivum L.) is produced in arid and semi‐arid regions around the world, and water scarcity poses a constant threat to yields, with global climate change and population growth exacerbating this vulnerability. Thus, breeding drought‐tolerant germplasm to improve yields in arid regions represents an important goal of wheat breeding programs. However, drought tolerance is a complex quantitative trait controlled by numerous genes that are involved in multiple drought-responsive signaling pathways and metabolic networks. Defining the genetic and molecular mechanisms responsible for drought tolerance is a necessary step towards accelerating breeding.

Question: What are the key regulatory genes responsible for variation in drought tolerance in wheat and how do they function in conferring a tolerant phenotype? This study aimed to identify genetic components contributing to variation in wheat drought tolerance and to develop molecular markers to facilitate development of elite drought tolerant wheat varieties.

Findings: Through a genome-wide association study and candidate gene association analysis, we identified a 26-bp deletion in the TaDTG6-B coding region that induces a gain-of-function for the encoded TaDTG6-B^Del574 protein, a transcription factor tightly associated with drought tolerance in wheat. TaDTG6-B^Del574 exhibits stronger transcriptional activation, more protein interactions, and higher binding activity to DRE/CRT cis-elements than the TaDTG6-B^In574 that lacks the deletion. TaDTG6-B^Del574 knockdown attenuated drought tolerance in transgenic wheat, whereas its overexpression led to significantly enhanced drought tolerance. No effect on drought tolerance was associated with changes in expression of TaDTG6-B^In574 allele. TaDTG6-B^Del574 positively regulated TaPIF1 expression, thereby enhancing wheat drought tolerance. Furthermore, introgression of the TaDTG6-B^Del574 elite allele into drought-sensitive cultivars improved their drought tolerance, thus providing a valuable genetic resource for wheat breeding.

Next steps: Future and ongoing research will involve the determination of the crystal structure of TaDTG6-B variants and how they relate to drought tolerance in wheat. We also seek to dissect the regulatory networks between TaDTG6-B^Del574 and other drought-responsive genes.

Reference:

Fangming Mei, Bin Chen, Linying Du, Shumin Li, Dehe Zhu, Nan Chen, Yifang Zhang, Fangfang Li, Zhongxue Wang, Xinxiu Cheng, Li Ding, Zhensheng Kang, Hude Mao (2022) A gain-of-function allele of a DREB transcription factor gene ameliorates drought tolerance in wheat https://doi.org/10.1093/plcell/koac248