Fine mapping and characterization of the awn inhibitor B1 locus in common wheat(Triticum aestivum L.)

Awns play an important role in seed dispersal and photosynthesis of spikes.Three major awn inhibitors(Hd,B1,and B2)are reported in wheat.However,the molecular mechanism underlying awnlessness remained unknown until recently.In this study,we identified two F8 recombinant inbred lines(RILs)that were segregating for awn length.In order to identify the causal gene for awn length in the heterozygous inbred families(HIFs),SNPs were called from RNA sequencing(RNA-Seq)data for HIF-derived progenies with long and short awns.SNPs between long and short awn plants were evenly distributed on chromosomes(chr)other than chromosome 5 A.SNPs on chr 5 A were clustered in a region distal 688 Mb on the long arm,where inhibitor B1 was located.This suggested that B1 was the causal segregating locus.We precisely mapped B1 to^1 Mb region using two HIF-derived families.Considering that the lines segregated for long,intermediate and short awn phenotypes we speculated that B1 should have a dosage effect on awn length.Two differentially expressed genes(DEGs)located in the candidate region were regarded as candidate genes for B1,because the molecular expression pattern was consistent with the phenotype.HIFs with long and short awns showed no difference on grain yield and other agronomic traits.

Comparative genomic and transcriptomic analyses uncover the molecular basis of high nitrogen-use efficiency in the wheat cultivar Kenong 9204

Studying the regulatory mechanisms that drive nitrogen-use efficiency(NUE)in crops is important for sustainable agriculture and environmental protection.In this study,we generated a high-quality genome assembly for the high-NUE wheat cultivar Kenong 9204 and systematically analyzed genes related to nitrogen uptake and metabolism.By comparative analyses,we found that the high-affinity nitrate transporter gene family had expanded in Triticeae.Further studies showed that subsequent functional differentiation endowed the expanded family members with saline inducibility,providing a genetic basis for improving the adaptability of wheat to nitrogen deficiency in various habitats.To explore the genetic and molecular mechanisms of high NUE,we compared genomic and transcriptomic data from the high-NUE cultivar Kenong 9204(KN9204)and the low-NUE cultivar Jing 411 and quantified their nitrogen accumulation under high-and low-nitrogen conditions.Compared with Jing 411,KN9204 absorbed significantly more nitrogen at the reproductive stage after shooting and accumulated it in the shoots and seeds.Transcriptome data analysis revealed that nitrogen deficiency clearly suppressed the expression of genes related to cell division in the young spike of Jing 411,whereas this suppression of gene expression was much lower in KN9204.In addition,KN9204 maintained relatively high expression of NPF genes for a longer time than Jing 411 during seed maturity.Physiological and transcriptome data revealed that KN9204 was more tolerant of nitrogen deficiency than Jing 411,especially at the reproductive stage.The high NUE of KN9204 is an integrated effect controlled at different levels.Taken together,our data provide new insights into the molecular mechanisms of NUE and important gene resources for improving wheat cultivars with a higher NUE trait.