Natural variations of ZmSRO1d modulate the trade-off between drought resistance and yield by affecting ZmRBOHC-mediated stomatal ROS production in maize

While crop yields have historically increased,drought resistance has become a major concern in the context of global climate change.The trade-off between crop yield and drought resistance is a common phenomenon;however,the underlying molecular modulators remain undetermined.Through genome-wide association study,we revealed that three non-synonymous variants in a drought-resistant allele of ZmSRO1d-R resulted in plasma membrane localization and enhanced mono-ADP-ribosyltransferase activity of ZmSRO1d toward ZmRBOHC,which increased reactive oxygen species(ROS)levels in guard cells and promoted stomatal closure.ZmSRO1d-R enhanced plant drought resilience and protected grain yields under drought conditions,but it led to yield drag under favorable conditions.In contrast,loss-of-function mutants of ZmRBOHC showed remarkably increased yields under well-watered conditions,whereas they showed compromised drought resistance.Interestingly,by analyzing 189 teosinte accessions,we found that the ZmSRO1d-R allele was present in teosinte but was selected against during maize domestication and modern breeding.Collectively,our work suggests that the allele frequency reduction of ZmSRO1d-R in breeding programs may have compromised maize drought resistance while increased yields.Therefore,introduction of the ZmSRO1d-R allele into modern maize cultivars would contribute to food security under drought stress caused by global climate change.

A natural variation in Ribonuclease H-like gene underlies Rht8 to confer“Green Revolution”trait in wheat

Dear Editor,Introduction of gibberellin(GA)-insensitive Reduced height(Rht)genes,Rht-B1b and Rht-D1b,has resulted in the“Green Revolution”in modern wheat cultivars(Triticum aestivum)that has skyrocketed wheat grain yields worldwide since the 1960s(Peng et al.,1999;Velde et al.,2021).However,Rht-B1b/D1b also reduce coleoptiles,which is undesired in dryland regions where deep planting is essential for seedling establishment(Rebetzke et al.,1999,Rebetzke et al.,2001;Ellis et al.,2004).

Coronatine promotes maize water uptake by directly binding to the aquaporin ZmPIP2;5 and enhancing its activity

Water uptake is crucial for crop growth and development and drought stress tolerance. The water channel aquaporins(AQP) play important roles in plant water uptake. Here, we discovered that a jasmonic acid analog, coronatine(COR), enhanced maize(Zea mays) root water uptake capacity under artificial water deficiency conditions. COR treatment induced the expression of the AQP gene Plasma membrane intrinsic protein 2;5(ZmPIP2;5).In vivo and in vitro experiments indicated that COR also directly acts on ZmPIP2;5 to improve water uptake in maize and Xenopus oocytes. The leaf water potential and hydraulic conductivity of roots growing under hyperosmotic conditions were higher in ZmPIP2;5-overexpression lines and lower in the zmpip2;5 knockout mutant, compared to wild-type plants. Based on a comparison between ZmPIP2;5 and other PIP2s, we predicted that COR may bind to the functional site in loop E of ZmPIP2;5. We confirmed this prediction by surface plasmon resonance technology and a microscale thermophoresis assay, and showed that deleting the binding motif greatly reduced COR binding. We identified the N241 residue as the COR-specific binding site, which may activate the channel of the AQP tetramer and increase water transport activity,which may facilitate water uptake under hyperosmotic stress.