Trans-QTL alliance of HKT1 and PHL7 modulate salinity stress tolerance and enhance crop yield endurance

Abstract

Salinity stress can cause significant yield losses in crops because of its major impact on reproductive success. The complexity of salinity stress responses, particularly their tissue- and cell-specific regulation, continues to challenge the translation of molecular insights into tangible crop yield improvements. In the present study, the authors deployed a genomic strategy combining a genome-wide association study, regional association analysis, QTL mapping, fine mapping, and map-based cloning to delineate a pair of novel CaPHL7 and CaHKT1 alleles that regulate yield under salinity stress. The selected contrasting accessions, developed near-isogenic lines (NILs), overexpressed chickpea lines and complemented Arabidopsis lines collectively underscore the functional significance of the identified alleles in relaying yield endurance under salinity stress conditions. Functional characterisation of the genes revealed the intricate transcriptional regulation of CaHKT1 by CaPHL7, which influences the degree of salinity stress tolerance. Furthermore, in our efforts to enhance yield endurance, we discovered a novel regulatory role for the phosphorus (P) starvation-responsive gene (PHL7) in legumes, facilitating salinity stress adaptation. This study provides the first functional validation of a trans-QTL regulatory model in chickpea, where CaPHL7, located on one chromosome, transcriptionally activates CaHKT1 on a separate chromosome. The regulatory mechanism plays a key role in excluding sodium from the transpiration stream, thereby protecting reproductive processes from salinity-induced damage and mitigating yield penalties. This inter-locus regulation explains yield stability and offers useful insights that may be considered in future efforts to enhance salt resilience in chickpea.