TaFAR5-TaFAR3 module regulates cuticular wax biosynthesis and drought tolerance in wheat

Plant cuticular waxes function as a protective barrier to mitigate environmental stresses, especially water deficit, although the molecular mechanisms and natural genetic variations underlying wax accumulation in crops remain unclear. Our genome-wide association study (GWAS) of the contents of cuticular wax components in wheat seedlings demonstrated that allelic variations in TaFAR5, encoding a fatty acyl-CoA reductase, contribute to the differences in leaf cuticular wax accumulation. Molecular and transgenic analyses revealed that variations in the TaFAR5 promoter affect the binding affinity between cis-regulatory elements and several transcription factors, including TaLBD16, TaERF12, TaNAC2, TaWRKY2, TaMYBC1, and TaNAC6, consequently modulating TaFAR5 expression. Interestingly, allelic variations in the TaFAR5 coding sequence induce amino acid substitutions that promote interaction between TaFAR5 and TaFAR3, which in turn significantly boost biosynthesis of primary alcohol components of cuticular wax. Moreover, TaFAR5 or TaFAR3 knockout attenuates drought stress tolerance, while their overexpression remarkably enhances drought tolerance in wheat seedlings by reducing water loss. Additionally, we found that the favorable TaFAR5 allele is widely distributed in tetraploid wheat but has limited distribution in hexaploid accessions, occurring at higher frequency in arid regions. Taken together, this study demonstrates how natural variations in TaFAR5-TaFAR3 regulatory module impact leaf cuticular wax biosynthesis to confer drought tolerance in wheat.