GmAIR12-5 governs soybean nodule development associated with phosphorus availability

Low phosphorus (P) bioavailability limits nitrogen (N) fixation in legume nodules. Although auxin-induced root 12 (AIR12) contributes to plant stress resistance, its role in regulating nodule adaptation to P deficiency remains elusive. In this study, a hydroponic experiment revealed that P deficiency restricted soybean (Glycine max) growth and decreased nodule development, especially in big nodules (diameter≥2 mm). Following analyzing the phylogenetic relationship and expression pattern, we identified that GmAIR12-5 might be highly expressed in nodules and associated with nodule development. Overexpression of GmAIR12-5 led to significant increases in plant growth and acquisition of N and P in soybean, particularly under low-P conditions. Conversely, suppression of GmAIR12-5 reduced the plant growth and nutrients absorption of soybean. Significantly, under low-P levels, overexpression of GmAIR12-5 increased the number and weight of big nodules by 67.7 % and 67.4 %, respectively, while nodule development was inhibited by GmAIR12-5 suppression. In contrast, under high-P conditions, GmAIR12-5 mutants only exhibited significant alterations in root architecture and nodule weight, while maintaining comparable shoot biomass and nodule number to wild type. Furthermore, the overexpression of GmAIR12-5 significantly down-regulated the superoxide anion content and enhanced the number of infected cells under low P conditions. These results demonstrate that GmAIR12-5 contributes to nodule development by avoiding reactive oxygen species accumulation. This finding enhances our understanding of the role of AIR12 in legume crops.