Natural alleles of Mediator subunit genes modulate plant height in chickpea

Abstract

Plant height (PH) is an important plant architectural trait targeted during Green Revolution to enhance crop yields. Identification of genes and natural alleles governing plant height without compromising agronomic performance can fill the lacuna of knowledge connecting ideal plant architecture with maximum achievable yield in chickpea. Through coherent strategy involving genome-wide association study, QTL/fine mapping, map-based cloning, molecular haplotyping, and downstream functional genomics, the current study identified two Mediator subunit genes namely, CaMED23 and CaMED5b and their derived natural alleles/haplotypes underlying the major QTLs and trans-acting eQTLs regulating plant height in chickpea. Differential accumulation of haplotype-specific transcripts of these two Mediator genes in corresponding haplotype-introgressed near-isogenic lines (NILs) correlates negatively with the plant height trait. Quantitative as well as qualitative estimation based on histology, scanning electron microscopy, and histochemical assay unraveled the reduced lengths and cell sizes of internodes along with compromised lignin levels in dwarf/semi-dwarf chickpea NILs introgressed with superior CaMED23 and CaMED5b gene haplotypes. This observation, supported by global transcriptome profiling-based diminished expression of various phenylpropanoid pathway genes upstream of lignin biosynthesis in dwarf/semi-dwarf NILs, essentially links plant height with lignin accumulation. The identified molecular signatures in the Mediator subunit genes can be efficiently utilized to develop desirable dwarf/semi-dwarf-type chickpea cultivars without affecting their yield per plant via modulating lignin/phenylpropanoid biosynthesis.