Rice OVATE family protein 6 regulates plant development and confers resistance to drought and cold stresses.

OVATE family proteins (OFPs) regulate multiple aspects of plant growth and development; however, their roles in responses to abiotic stresses have not yet been studied. Here, we report that rice OsOFP6 regulates growth and development, and alters responses to drought and cold stresses. OsOFP6 is expressed in various tissues and developmental stages. Knock-down of OsOFP6 by RNA interference (RNAi) resulted in semi-dwarf stature, altered grain shape, and shorter lateral roots. OsOFP6 was shown to interfere with auxin in regulating lateral root growth and initiation, as RNAi plants had increased density of lateral roots under IAA (indole-3-acetic acid) treatment. OsOFP6 also affects polar auxin transport, which was demonstrated by the different responses of RNAi and OsOFP6-overexpression (OE) plants to treatment with N-1-naphthylphalamic acid (NPA). Furthermore, under drought conditions OE lines showed slower water loss and less accumulation of H2O2 compared with RNAi plants, which displayed faster water loss and higher H2O2, implying that OsOFP6 may confer both drought avoidance and drought tolerance in rice plants. In addition, under cold treatment OE and RNAi plants exhibited lower and higher relative electrical conductivity (REC), respectively, suggesting an important role of OsOFP6 in response to cold stress. These results provide new insights into the multiple functions of OVATE family proteins.