Characterization of wheat cell wall invertase genes associated with drought tolerance in synthetic-derived wheat

Cell wall invertase (CWI) gene hydrolyzes sucrose into glucose and fructose that supports pollen development. Down regulation of CWI is responsible for drought induced pollen sterility which ultimately reduces grain yield by limiting grain numbers. In bread wheat, CWI gene has been localized on chromosomes 4A, 5B and 5D which have conserved WECPDF domain. In synthetic derived wheat (SYN-DER) diversity panel, 123 accessions had Hap-4A-C haplotype at TaCwi-Al which was significantly associated with 1000 grain weight (TGW) and other agronomic traits under both well-water and water-limited conditions. On the other hand, Hap-SD-C haplotype was fixed at TaCwi-D1 in synthetic derivatives. Previous studies identified high sequence conservation at TaCwi-B1, however sequencing of this gene in diverse SYN-DER identified several mutations putatively transferred from durum parents of synthetic hexaploid wheats. The non-synonymous substitutions observed in TaCwi-B1 in the conserved domain (WECPDF) were Glu372Lys, Glu372Gly, Pro374Gln, Asp375Thr, while Phe376Leu, Tyr377Thr, Val379Cys variants were observed in the neighboring region. In silico analysis revealed that these point mutations sequentially and structurally influenced the biological function of TaCwi-B1 protein. All the identified mutations caused poor hydrolysis of sucrose followed by improper pollen development which had implications in wheat drought adaptability. In addition, G320C allelic variant was found in high percentage (54%) in SYN-DERs. The association analysis confirmed that SNP TaCwi-B1-G enhanced TGW and grain yield in SYN-DERs. Our results significantly enhance the understanding of gene function affecting drought adaptability in wheat