Isoforms of plasma membrane H(+)-ATPase in rice root and shoot are differentially induced by starvation and resupply of NO₃⁻ or NH₄+.

The goal of this study was to evaluate the effects of nitrogen starvation and resupply in 10 PM H+-ATPase isoforms and the expression of NO₃⁻ and NH₄+ transporters in rice. The net uptake of both forms of NO₃⁻-N or NH₄+-N was increased with its resupply. Resupply of NO₃⁻ resulted in induction of the following PM H+-ATPase isoforms, OsA1, OsA2, OsA5 and OsA7 in the shoots and OsA2, OsA5, OsA7 and OsA8 in the roots. Resupply of NH₄+ resulted in the induction of the following OsA1, OsA3 and OsA7 isoforms in the roots while OsA1 was induced in the shoots. It was observed that increased PM H+-ATPase activity also resulted in increased net uptake of NO₃⁻ and NH₄+. In the roots, OsNRT2.1 and OsNRT2.2 were induced by NO₃⁻ resupply, while OsAMT1.1 and OsAMT1.2 were induced by NH₄+ deficiency. The results showed that the expression of PM H+-ATPase isoforms is related to NO₃⁻ and NH₄+ transporters as well as in which section of the plant it takes place. PM H+-ATPase isoforms OsA2 and OsA7 displayed the strongest induction in response to N resupply, therefore indicating that these genes could be involved in N uptake in rice.