TITLE:
Studies on the Effects of OsRGA1 Involved in Responses to Low Phosphorus Stress in Rice
AUTHORS:
Mercy D. Menthee, Kang Xu, Sarkpa Eastgar Garmonee
KEYWORDS:
OsRGA1, Low Phosphorus Stress, Root Development, Antioxidant Enzymes, Acid Phosphatase, Phosphorus Transporter, Strigolactone, Rice
JOURNAL NAME:
Open Access Library Journal,
Vol.12 No.11,
November
28,
2025
ABSTRACT: Phosphorus (P) is an essential macronutrient that plays a critical role in plant growth, energy transfer, and metabolic regulation, yet its low availability in soils severely limits crop productivity. The heterotrimeric G protein α-subunit gene OsRGA1 has been implicated in nutrient signaling pathways, but its role in low phosphorus (LP) stress adaptation in rice remains insufficiently characterized. In this study, we investigated the functional contribution of OsRGA1 to LP stress responses using wild-type Nipponbare (NIP), OsRGA1 knockout mutants (R-5, R-8), and overexpression lines (ROE1, ROE2) grown hydroponically under normal phosphorus (NP, 300 μM KH2PO4) and LP (5 μM KH2PO4) conditions. Phenotypic analysis revealed that LP stress markedly promoted primary root elongation in all genotypes, with the most pronounced increase observed in ROE2 (56.14%) and the least in mutants R-5 and R-8 (23.73% and 21.14%, respectively). LP treatment significantly enhanced antioxidant enzyme activities (SOD, POD, CAT), acid phosphatase activity, and the expression of phosphorus transporter genes (OsPT2, OsPT6, OsPT8), while reducing root oxidation capacity. Notably, these LP-induced responses were amplified in overexpression lines, particularly ROE2, and attenuated in knockout mutants relative to NIP. Strigolactone (5DS) content also increased substantially under LP stress, with the magnitude of change correlating with OsRGA1 expression levels, suggesting hormonal cross-talk in root adaptive responses. Gene expression profiling demonstrated that OsRGA1 transcript abundance peaked at 5 μM P, confirming its sensitivity to LP conditions. The data collectively indicate that OsRGA1 acts as a positive regulator in LP stress adaptation by promoting primary root elongation, enhancing antioxidant defenses, stimulating acid phosphatase activity, and upregulating P transporter genes. These coordinated physiological and molecular adjustments improve phosphorus acquisition efficiency under nutrient-limited conditions. Our findings provide new insights into the regulatory network linking G protein signaling, hormonal pathways, and nutrient stress responses in rice. Targeted manipulation of OsRGA1 may represent a promising strategy for breeding rice cultivars with improved phosphorus-use efficiency, contributing to sustainable agricultural productivity in P-deficient soils.