Jasmonate ZIM-domain (JAZ) proteins are key repressors of the jasmonate signaling pathway and are involved in plant stress responses. However, their roles in starch biosynthesis in cereal crops remain unclear. In this study, we identified a locus associated with starch content on chromosome 5A by a genome-wide association study (GWAS). At this locus, a gene (TraesCS5A02G204900) encoding a JAZ protein (TaJAZ1) was found to be highly expressed in grains. CRISPR/Cas9-induced mutants were generated to investigate the role of TaJAZ1 in starch biosynthesis. Phenotypic characterization revealed significant alterations in starch granule size, crystallinity, and digestibility. Specifically, the two mutant lines (tajaz1-abd#1 and tajaz1-abd#2) exhibited increased total starch (12.5% and 17.6%, respectively), amylose (79.3% and 72.1%, respectively), resistant starch (88.5% and 96.8%, respectively), and grain yield per plant (103.8% and 58.8%, respectively). Furthermore, the mutation of TaJAZ1 significantly increased the expression levels of TaSBEI, TaAGPS1, TaAGPL1 and TaGBSSI, but decreased the expression levels of TaSSIIa, TaSSIIb and TaSBEIIa by binding to their promoters. Taken together, our results demonstrate that TaJAZ1 is a negative regulator of starch biosynthesis and grain yield. These findings not only provide novel insights into wheat starch biosynthesis regulation, but also contribute to potential genes for breeding wheat varieties of better quality and higher yield.

One of agriculture’s major challenges is the low efficiency of phosphate (Pi) use, which leads to increased costs, harmful environmental impacts, and the depletion of phosphorus (P) resources. The TaPHT1;6 gene, which encodes a high-affinity Pi transporter (PHT), plays a crucial role in Pi absorption and transport. In this study, the promoter and coding regions of three TaPHT1;6 gene copies on chromosomes 5A, 5B, and 5D were individually amplified and sequenced from 167 common wheat (Triticum aestivum L.) cultivars. Sequence analysis revealed 16 allelic variation sites within the promoters of TaPHT1;6-5B among these cultivars, forming three distinct haplotypes: Hap1, Hap2, and Hap3. Field trials were conducted over two years to compare wheat genotypes with these haplotypes, focusing on assessing plant dry weight, grain yield, P content, Pi fertilizer absorption efficiency, and Pi fertilizer utilization efficiency. Results indicated that Hap3 represented the favored Pi-efficient haplotype. Dual-luciferase reporter assay demonstrated that the Hap3 promoter, carrying the identified allelic variation sites, exhibited higher gene-driven capability, leading to increased expression levels of the TaPHT1;6-5B gene. We developed a distributed cleaved amplified polymorphic site marker (dCAPS-571) to distinguish Hap3 from the other two haplotypes based on these allelic variation sites, presenting an opportunity for breeding Pi-efficient wheat cultivars. This study successfully identified polymorphic sites on TaPHT1;6-5B associated with Pi efficiency and developed a functional molecular marker to facilitate future breeding endeavors.