The leucine-rich repeat receptor-like kinase AhZAR1 regulates early seed development in peanut

Peanut (Arachis hypogaea L.) serves as a vital oilseed and food crop worldwide. Embryo abortion reduces seed set in peanut and significantly limits yields, but the mechanisms responsible have remained unclear. Here, we examined an ethyl methanesulfonate (EMS)-induced peanut mutant exhibiting early embryo abortion and a partially single-seeded pod phenotype. Cytological analysis indicated that seed abortion in the mutant begins at the proembryo stage, 7 d after flowering, with noticeable degeneration by 3 d after peg penetration into the soil (DAP), culminating in complete arrest by 10 DAP. Transcriptomic analysis identified 8778 differentially expressed genes (DEGs) during the transition from aerial to subterranean peg development in the mutant. These DEGs were significantly enriched for pathways such as MAPK signaling, auxin biosynthesis and transport, and calcium transport. Notably, we identified a premature stop codon mutation (C > T) in AhZAR1-4 of the mutant; this gene encodes a leucine-rich repeat receptor-like kinase. The mutation resulted in the truncation of the kinase and transmembrane domains of AhZAR1-4, leading to a loss of membrane localization and protein function. In yeast two-hybrid screening, AhZAR1-4 interacted with both AhIAA31 and AhBSK2. Heterologous overexpression of AhZAR1-4_wt successfully rescued the seed-abortion phenotype of the Arabidopsis thaliana atzar1-4 mutant and increased seed size, whereas AhZAR1-4_mut expression did not. These findings identify AhZAR1-4 as a crucial regulator of seed development in peanut, making it a promising genetic target for improving pod yield and seed setting rate.