Heterotrimeric G protein is involved in plant growth and development, while the role of rice (
Oryza sativa) G protein γ subunit
qPE9-1 in response to low-phosphorus (LP) conditions remains unclear. The gene expression of
qPE9-1 was significantly induced in rice roots under LP conditions. Rice varieties carrying the
qPE9-1 allele showed a stronger primary root response to LP than the varieties carrying the
qpe9-1 allele (mutant of the
qPE9-1 allele). Transgenic rice plants with the
qPE9-1 allele had longer primary roots and higher P concentrations than those with the
qpe9-1 allele under LP conditions. The plasma membrane (PM) H
+-ATPase was important for the
qPE9-1-mediated response to LP. Furthermore, OsGF14b, a 14-3-3 protein that acts as a key component in activating PM H
+-ATPase for root elongation, is also involved in the qPE9-1 mediation. Moreover, the overexpression of
OsGF14b in WYJ8 (carrying the
qpe9-1 allele) partially increased primary root length under LP conditions. Experiments using R18 peptide (a 14-3-3 protein inhibitor) showed that
qPE9-1 is important for primary root elongation and H
+ efflux under LP conditions by involving the 14-3-3 protein. In addition, rhizosheath weight, total P content, and the rhizosheath soil Olsen-P concentration of
qPE9-1 lines were higher than those of
qpe9-1 lines under soil drying and LP conditions. These results suggest that the G protein γ subunit
qPE9-1 in rice plants modulates root elongation for phosphorus uptake by involving the 14-3-3 protein OsGF14b and PM H
+-ATPase, which is required for rice P use.
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