Two quantitative trait loci for abscisic acid responsiveness differentially regulate stress responses at the early seedling stage and seed dormancy in common wheat

Abscisic acid (ABA) is an important phytohormone in abiotic stress tolerance, germination and seed dormancy. Several quantitative trait loci (QTLs) for ABA responsiveness at the early seedling stages have been reported in common wheat, and two of them were assigned to chromosomes 2A and 3A. For functional characterization of the 2A and 3A QTLs, near-isogenic lines (NILs) for the ABA responsiveness QTL were here developed by repeatedly backcrossing recombinant inbred lines between two wheat cultivars showing distinct ABA-responsiveness levels, Mironovskaya 808 (M808) and Chinese Spring (CS), with CS. Higher ABA responsiveness and seed dormancy were observed in the NILs with the M808 allele than in those with the CS allele in the two QTLs. RNA sequencing analysis showed that the 2A and 3A QTLs partly regulate common ABA signal pathways including the bZIP transcription factor-mediated transcriptional regulation of LEA genes, and that the 2A and 3A QTLs also control distinct gene families in the downstream target genes in the wheat seedlings. Moreover, the downstream genes exhibiting significantly distinct ABA-responsive expression patterns between the NILs with the M808 allele and those in CS were observed. Thus, the 2A and 3A QTLs partly controlled functionally different genes through distinct ABA signal pathways. Our results exhibited functional association of the 2A and 3A QTLs with the connection between ABA responsiveness and seed dormancy. In addition, the two QTLs play partly distinct roles in the ABA signal pathways at the wheat seedling stages.