Pseudomonas atacamensis SJA1 enhances root development and phosphorus accumulation in rice under organic fertilization.

Pseudomonas-based biofertilizers show strong potential in sustainable agriculture; however, their effects on rice growth and nutrient acquisition under organic fertilization remain insufficiently characterized. This study evaluated the effects of Pseudomonas atacamensis SJA1 (CGMCC No. 26128) on rice growth and nutrient accumulation using a pot experiment with four treatments: organic fertilizer (CK), SJA1 inoculation (S), mixed commercial biofertilizer (MC, Bacillus subtilis and Pseudomonas atacamensis), and a combination of organic fertilizer, SJA1 inoculation, and commercial biofertilizer (SC). Plant biomass and nutrient content were measured, and the expression of nutrient-related genes (OsMGD2, OsMGD3, OsPHO2, OsPHR2, OsSAE1a, and OsSIZ2) in leaves and roots was analyzed using qRT-PCR. Whole-genome sequencing and functional annotation of SJA1 were conducted to identify traits associated with plant growth promotion. SJA1 inoculation significantly increased root biomass and enhanced phosphorus accumulation and increased nitrogen accumulation particularly in roots. SJA1 inoculation strongly induced the expression of several phosphorus- and nutrient-responsive genes in roots, including OsPHR2, OsPHO2, OsSAE1a, OsSIZ2, and OsMGD3. Genomic analysis identified genes in SJA1 associated with phosphate solubilization (e.g., gcd and the pqq operon), nitrogen metabolism, and rhizosphere colonization. These results indicate that SJA1 enhances root development and phosphorus accumulation in rice under organic fertilization, and suggest potential roles in plant nutrient acquisition, although the underlying processes require further validation.