Calcium-dependent protein kinases (CDPKs) function as key sensors of Ca²⁺ signals in plants; however, their roles in soybean-rhizobial symbiosis and biological nitrogen fixation remain poorly understood. This study demonstrates that GmCDPK14, a member of the soybean CDPK gene family, is specifically induced following rhizobial infection and is predominantly expressed in primary root tissues and nodules. Functional analyses revealed that GmCDPK14 plays a positive regulatory role in symbiotic nodulation. Loss-of-function mutants showed substantial decreases in nodule number, root dry weight, shoot dry weight, nitrogenase activity, and infection thread formation, whereas overexpression of GmCDPK14 produced the opposite effects. Transcriptomic analysis showed that GmRINRK1, a key symbiotic gene, was significantly downregulated in GmCDPK14-deficient lines. Moreover, overexpression of GmRINRK1 in the Gmcdpk14 mutant background partially rescued the nodulation defects. These results suggest that GmCDPK14 enhances soybean-rhizobium symbiotic nodulation by positively regulating GmRINRK1 expression, offering new insights into the role of CDPKs in controlling legume-rhizobium interactions.

Phytophthora sojae infection severely impairs soybean production. We previously identified a dirigent protein, GmDRR1 (Glycine max Disease Resistant Response 1), that increases soybean resistance to P. sojae. However, the molecular basis of GmDRR1 function remained largely uncharacterized. In the present study, analysis of GmDRR1-RNAi, GmDRR1-overexpressing, and CRISPR/Cas9-derived Gmdrr1 mutant lines revealed that GmDRR1 expression significantly restricted P. sojae growth. Combining co-immunoprecipitation with liquid chromatography–tandem mass spectrometry revealed a GmDRR1-interacting protein, GmDRR2, which is homologous to GmDRR1. An E-coniferyl alcohol coupling assay indicated that GmDRR1 promotes the synthesis of (+)-pinoresinol, which helps to protect plants from P. sojae. The GmNAC1 (Glyma.05G025500) transcription factor bound to the GmDRR1 promoter both in vitro and in vivo to upregulate GmDRR1 expression. Soybean resistance to P. sojae was increased by overexpression of GmNAC1. Our findings suggest a novel signaling pathway involving a NAC transcription factor that mediates soybean resistance to P. sojae. Specifically, GmNAC1 directly induces GmDRR1 expression to increase resistance of soybean plants to P. sojae.