The allelic mutation of NBS-LRR gene causes premature senescence in wheat

Premature senescence has a significant impact on the yield and quality of wheat crops. The process is controlled by multiple and intricate genetic pathways and regulatory elements, whereby the discovery of additional mutants provides important insights into the molecular basis of this important trait. Here, we developed a premature senescence wheat mutant je0874, its leaves started to show yellow before heading stage; with plant growth and development, the degree of yellowing worsened rapidly, and chlorophyll content in flag leaf was reduced by 93.8% at 15 days after heading, all other leaves became dryness at the grain filling stage. In the mutant, the reactive oxygen species (ROS) and its metabolites increased up to 34.8%~47.3%, while activities of ROS scavenging enzymes were reduced by 62.7% to 96.7%. Premature senescence resulted in a reduction of thousand grain weight by over 50%. Genetic analysis showed the mutation of senescence was controlled by a single recessive gene, and target gene was finely mapped to a 338kb region of the long arm of chromosome 2D. This region contained a total of 6 annotated genes, while only gene TraesFLD2D01G513900 carried a SNP mutation. The gene contained an NBS-LRR domain, we named it Taps1. Allelic mutants of Taps1 exhibited a lesion mimic phenotype, and the mutant allele resulted in cell death in tobacco, which represent a novel gene controlling wheat senescence. Two haplotypes were identified in 180 accessions, which did not lead to cell death. These results contribute to increase our understanding of the regulation of premature plant senescence.