Serendipita indica promotes rice phosphorus uptake by plasma membrane H+-ATPase OsA1-stimulated root hair growth

Plasma membrane (PM) H+-ATPase is important for plant phosphorus (P) uptake. The endophytic fungus Serendipita indica (S. indica) can increase plant P acquisition under P deficiency conditions, but it is unclear whether PM H+-ATPase OsA1 is involved in S. indica-modulated P uptake in rice. Under low-P conditions, rice seedlings inoculated with S. indica showed a 90% increase in shoot P concentration and a 164% increase in root P concentration compared with the non-inoculated rice, largely due to significantly elongated root hairs. The relative expression of OsA1 in S. indica-inoculated plants was 73.2% higher than in non-inoculated S. indica plants under low-P conditions. Under low-P conditions, S. indica inoculation also enhanced root H+ efflux by 34% and PM H+-ATPase activity by 27% in wild-type rice compared with non-inoculated plants, whereas no such significant difference was observed in the osa1-1 or osa1-2 mutants. Taken together, our results suggest that S. indica promotes root hair growth under low-P conditions by modulating plasma membrane H+-ATPase OsA1. This cooperative interaction reveals a key mechanism through which S. indica enhances P acquisition, providing valuable insights for improving P-use efficiency in rice production.