Improvement of wheat drought tolerance through editing of TaATX4 by CRISPR/Cas9

Wheat(Triticum aestivum L.)is a staple cereal crop grown in arid and semi-arid areas worldwide and provides a major source of nutrition globally.However,its production is often affected by drought or water deficit,a problem which is expected to worsen because of climate change and a rapidly expanding global population;for example,the demand for agricultural water supplies is projected to increase by an estimated 17%by 2025 to compensate for global population growth(Lesk et al.,2016;Hickey et al.,2019.

Wheat adaptation to environmental stresses under climate change:Molecular basis and genetic improvement

Wheat(Triticum aestivum)is a staple food for about 40%of the world’s population.As the global population has grown and living standards improved,high yield and improved nutritional quality have become the main targets for wheat breeding.However,wheat production has been compromised by global warming through the more frequent occurrence of extreme temperature events,which have increased water scarcity,aggravated soil salinization,caused plants to be more vulnerable to diseases,and directly reduced plant fertility and suppressed yield.One promising option to address these challenges is the genetic improvement of wheat for enhanced resistance to environmental stress.Several decades of progress in genomics and genetic engineering has tremendously advanced our understanding of the molecular and genetic mechanisms underlying abiotic and biotic stress responses in wheat.These advances have heralded what might be considered a“golden age”of functional genomics for the genetic improvement of wheat.Here,we summarize the current knowledge on the molecular and genetic basis of wheat resistance to abiotic and biotic stresses,including the QTLs/genes involved,their functional and regulatory mechanisms,and strategies for genetic modification of wheat for improved stress resistance.In addition,we also provide perspectives on some key challenges that need to be addressed.

Variation in cis-regulation of a NAC transcription factor contributes to drought tolerance in wheat

Drought is a major environmental factor limiting wheat production worldwide,and developing drought-tolerant cultivars is a central challenge for wheat breeders globally.Therefore,it is important to identify genetic components determining drought tolerance in wheat.In this study,we identified a wheat NAC gene(TaNAC071-A)that is tightly associated with drought tolerance by a genome-wide association study.Knockdown of TaNAC071-A in wheat attenuated plant drought tolerance,whereas its overexpression significantly enhanced drought tolerance through improved water-use efficiency and increased expression of stress-responsive genes.This heightened water-saving mechanism mitigated the yield loss caused by water deficit.Further candidate gene association analysis showed that a 108-bp insertion in the promoter of TaNAC071-A alters its expression level and contributes to variation in drought tolerance among wheat accessions.This insertion contains two MYB cis-regulatory elements(CREs)that can be directly bound by the MYB transcription activator,TaMYBL1,thereby leading to increased TaNAC071-A expression and plant drought tolerance.Importantly,introgression of this 108-bp insertion allele,TaNAC071-AIn-693,into drought-sensitive cultivars could improve their drought tolerance,demonstrating that it is a valuable genetic resource for wheat breeding.Taken together,our findings highlight a major breakthrough in determining the genetic basis underlying phenotypic variation in wheat drought tolerance and showcase the potential of exploiting CRE-containing indels for improving important agronomical traits.