Wheat genomic study for genetic improvement of traits in China

Bread wheat(Triticum aestivum L.)is a major crop that feeds 40%of the world’s population.Over the past several decades,advances in genomics have led to tremendous achievements in understanding the origin and domestication of wheat,and the genetic basis of agronomically important traits,which promote the breeding of elite varieties.In this review,we focus on progress that has been made in genomic research and genetic improvement of traits such as grain yield,end-use traits,flowering regulation,nutrient use efficiency,and biotic and abiotic stress responses,and various breeding strategies that contributed mainly by Chinese scientists.Functional genomic research in wheat is entering a new era with the availability of multiple reference wheat genome assemblies and the development of cutting-edge technologies such as precise genome editing tools,highthroughput phenotyping platforms,sequencing-based cloning strategies,high-efficiency genetic transformation systems,and speed-breeding facilities.These insights will further extend our understanding of the molecular mechanisms and regulatory networks underlying agronomic traits and facilitate the breeding process,ultimately contributing to more sustainable agriculture in China and throughout the world.

Ectopic expression of VRT-A2 underlies the origin of Triticum polonicum and Triticum petropavlovskyi with long outer glumes and grains

Polish wheat (Triticum polonicum) is a unique tetraploid wheat species characterized by an elongated outer glume. The genetic control of the long-glume trait by a single semi-dominant locus, P1 (from Polish wheat), was established more than 100 years ago, but the underlying causal gene and molecular nature remain elusive. Here, we report the isolation of VRT-A2, encoding an SVP-clade MADS-box transcription factor, as the P1 candidate gene. Genetic evidence suggests that in T. polonicum, a naturally occurring sequence rearrangement in the intron-1 region of VRT-A2 leads to ectopic expression of VRT-A2 in floral organs where the long-glume phenotype appears. Interestingly, we found that the intron-1 region is a key ON/OFF molecular switch for VRT-A2 expression, not only because it recruits transcriptional repressors, but also because it confers intron-mediated transcriptional enhancement. Genotypic analyses using wheat accessions indicated that the P1 locus is likely derived from a single natural mutation in tetraploid wheat, which was subsequently inherited by hexaploid T. petropavlovskyi. Taken together, our findings highlight the promoter-proximal intron variation as a molecular basis for phenotypic differentiation, and thus species formation in Triticum plants.

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).

Wheat male-sterile 2 reduces ROS levels to inhibit anther development by deactivating ROS modulator 1

Ms2 is an important dominant male-sterile gene in wheat,but the biochemical function of Ms2 and the mechanism by which it causes male sterility remain elusive.Here,we report the molecular basis underlying Ms2-induced male sterility in wheat.We found that activated Ms2 specifically reduces the reactive oxygen species(ROS)signals in anthers and thereby induces termination of wheat anther development at an early stage.Furthermore,our results indicate that Ms2 is localized in mitochondria,where it physically interacts with a wheat homolog of ROS modulator 1(TaRomo1).Romo1 positively regulates the ROS levels in humans but has never been studied in plants.We found that single amino acid substitutions in the Ms2 protein that rescue the ms2 male-sterile phenotype abolish the interaction between Ms2 and TaRomo1.Significantly,Ms2 promotes the transition of TaRomo1 proteins from active monomers to inactive oligomers.Taken together,our findings unravel the molecular basis of Ms2-induced male sterility and reveal a regulatory mechanism in which ROS act as essential signals guiding the anther development program in wheat.