| Wheat(Triticum aestivum)is one of the major grain crops in China,and ensuring stable wheat production is crucial for guaranteeing food security not only in China but also worldwide.However,the major wheat planting districts are scarce of water resources and suffered from serious drought,which severely impacts wheat yield with more than a 15%reduction.Therefore,deciphering the genetic basis of wheat’s resistance to stress,and identifying key genes and superior haplotypes that confer drought tolerance,is of great urgency and significance for genetic improvement and molecular breeding of drought-tolerant wheat.This study mined four major drought-tolerant quantitative trait loci(QTL)of wheat through a genome-wide association study(GWAS),among which the major QTL qDT4B on chromosome 4B accounts for 14.34%phenotypic variance explanation.This locus has been widely reported in hexaploid and tetraploid wheat over the past 15 years,and the drought-tolerant QTLs also exist in the colinear region of crops such as rice,indicating that this is a crucial and evolutionarily conservative drought-tolerant QTL.However,the drought-tolerant gene in this genetic locus has not been identified.This study found that the WD40 protein-coding gene TaWD40-4B.1 is the drought-tolerant gene in qDT4B.In the natural population of wheat,a nonsense mutation at the 1274th base of the TaWD40-4B.1 coding region results in premature termination of the coding region,leading to the formation of the full-length haplotype TaWD40-4B.1C and the truncated haplotype TaWD40-4B.1T.The nonsense mutation at this base is highly associated with the drought tolerance of the wheat natural population,and the wheat accessions carrying TaWD40-4B.1C show significantly higher drought tolerance than those carrying TaWD40-4B.1T.To comprehensively confirm the role of TaWD40-4B.1C and TaWD40-4B.1T in drought tolerance,this research used two wheat cultivars,Shanrong 3(carrying TaWD40-4B.1C haplotype)and Yangmai 20(carrying TaWD40-4B.1T haplotype),to construct TaWD40-4B.1C and TaWD40-4B.1T overexpression and RNAi lines.The results showed that TaWD40-4B.1C overexpression can improve drought tolerance and water-saving yield of wheat,while TaWD40-4B.1T has no significant effect.Genetic manipulation such as TaWD40-4B.1C overexpression and RNAi does not affect wheat growth and yield under well-watered conditions.At the same time,TaWD40-4B.1C can significantly improve the tolerance to salt,alkali,and heat,indicating that TaWD40-4B.1C has strong potential in the molecular breeding of broad-spectrum stress-tolerant wheat.The study found that TaWD40-4B.1C and TaWD40-4B.1T can specifically interact with the canonical catalases TaCATl and TaCAT3,but not with the non-canonical TaCAT2(with transnitrosylase activity).Furthermore,TaWD40-4B.1C shows a significantly stronger interaction with TaCAT1 and TaCAT3 than TaWD40-4B.1T.Further analysis revealed that as a molecular partner,TaWD40-4B.1C promotes the oligomerization of peroxidase,enhances its activity,lowers ROS levels under drought conditions,avoids excessive ROS accumulation,and improves the drought resistance of wheat.Haplotype tracing and distribution analysis showed that allelic variation of TaWD40-4B.1 occurred in hexaploid wheat.The proportion of TaWD40-4B.1T is higher in cultivars than in landraces,indicating that TaWD40-4B.1T has been selected during breeding.On the other hand,the proportion of drought-resistant haplotype TaWD40-4B.1C is negatively correlated with the mean annual rainfall in different wheat-growing areas,indicating that TaWD40-4B.1C has been more preserved in the drought-prone wheat breeding process.In summary,this study identified a new drought-resistant gene TaWD40-4B.1 and its drought-resistant haplotype in wheat and elucidated the molecular mechanism of TaWD40-4B.1 in the regulation of ROS homeostasis under drought(abiotic stress)conditions.This provides a new important genetic resource and editing target for the development of new drought-resistant wheat varieties. |
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