Peanuts (Arachis hypogaea L.) are a globally vital oilseed and economic crop, with China contributing over 35% of global production. Nonetheless, despite its agricultural importance, peanut yield is still constrained by embryo abortion, which leads to reduced seed set and the formation of empty pods. While environmental and nutritional factors have been implicated, the genetic mechanisms underlying this process have remained largely unknown. Now, researchers from Henan Agricultural University have identified a critical gene that controls early seed development, offering a tool for improving peanut yields.
The team set out to uncover the molecular basis of early seed abortion by studying a peanut mutant that produced partially single-seeded pods—a clear sign of developmental failure. "We discovered that in this mutant, embryo development goes awry just seven days after flowering, at a critical stage when the embryo begins to form," says Professor Dongmei Yin, corresponding author of the study published in The Crop Journal. "By comparing the gene expression patterns of normal and abortive seeds, we identified a gene, AhZAR1-4, that is essential for early embryogenesis."
The gene encodes a receptor-like kinase, a type of protein that sits on the cell membrane and helps cells perceive and respond to signals. In the mutant, a mutation (C to T) introduces a premature stop signal, truncating the protein and causing it to lose both its membrane anchor and its functional core.
"Through further functional studies, we confirmed the essential role of AhZAR1-4 in seed development," shares Yin. "We found that the AhZAR1-4 protein interacts with two other key proteins—AhIAA31 (an auxin-responsive protein) and AhBSK2 (a brassinosteroid-signaling kinase)—placing it at the crossroads of auxin and brassinosteroid signaling pathways, two major hormonal regulators of plant development."
Additionally, AhZAR1-4 was shown to regulate the expression of downstream genes in the MAPK signaling pathway (AhYDA and AhWOX8), a conserved module for embryonic polarity establishment in angiosperms.
Heterologous expression and complementation assays in Arabidopsis thaliana (thale cress, a small plant from the mustard family) solidified these findings: overexpression of the wild-type AhZAR1-4 gene not only rescued the seed abortion phenotype in an Arabidopsis ZAR1 mutant but also increased seed size in wild-type Arabidopsis. In contrast, the mutated AhZAR1-4 failed to complement the seed abortion defect, confirming that the loss of AhZAR1-4 function is directly responsible for the peanut mutant's abnormal seed development.
"Our study redefines the role of ZAR1 family genes in legume seed development," says Yin. "AhZAR1-4 is the first key gene identified in peanuts that regulates early embryo development by integrating multiple hormonal and signaling pathways, and its discovery provides a clear genetic target for molecular breeding to improve peanut seed set and yield."
