Soybean Gene Module Boosts Salt Tolerance and Fungal Resistance Without Sacrificing Yield

Abiotic stresses like soil salinity and biotic threats like fungal pathogens together cause massive crop yield losses globally. Soybean, a critical source of protein and oil, loses over 40% yield to salt stress and more than 15% to grey mould disease caused by Botrytis cinerea. Identifying genes that address both threat types simultaneously—without compromising normal growth—has been a major unmet challenge in crop biotechnology.

This study from Shandong University describes the discovery and functional characterization of GmST2, a NAC-family transcription factor in soybean (Glycine max) induced by both salt stress and B. cinerea infection. Using transgenic overexpression lines, CRISPR-Cas9 double knockout mutants (gmst2 gmst2h), and heterologous expression in Arabidopsis thaliana and Nicotiana tabacum, the researchers systematically established that GmST2 positively regulates plant growth, salt tolerance, and fungal resistance. Overexpressing GmST2 in soybean reduced photosystem II efficiency loss under 200 mM NaCl, improved antioxidant enzyme activities (SOD, CAT, POD), lowered malondialdehyde and Na⁺/K⁺ ratios, and increased proline accumulation. In field trials under saline conditions (0.25% total soluble salts), GmST2-OE plants were taller and produced significantly higher yields per plant.

RNA-sequencing of GmST2-overexpressing soybean revealed strong enrichment of jasmonic acid (JA) biosynthesis pathway genes. Mechanistically, GmST2 was shown to directly bind the promoters of GmAOC3 and GmAOC4, which encode allene oxide cyclase enzymes—key catalytic steps in JA biosynthesis—thereby elevating endogenous JA levels. This JA accumulation underpins both the salt tolerance and B. cinerea resistance phenotypes, establishing a clear biochemical mechanism.

The study further identified GmPRL1b, a WD40-repeat domain protein, as a nuclear interactor that stabilizes GmST2 protein and acts upstream in the regulatory cascade. Together, the GmPRL1b–GmST2–GmAOC3/4 module orchestrates JA-mediated cross-protection against concurrent abiotic and biotic stresses. Phylogenetic and evolutionary analyses showed that GmST2 was subject to selection pressure during soybean domestication, and an elite haplotype of GmST2 was associated with superior salt tolerance in natural soybean accessions, confirming agronomic relevance.

Unlike many stress-tolerance genes that impair growth under normal conditions, GmST2 overexpression enhanced plant growth even in non-stressed environments—a critical advantage for practical crop improvement. The module provides well-defined molecular targets for marker-assisted breeding or genetic engineering of stress-resilient soybeans, addressing the longstanding trade-off between stress resistance and productivity.