Overexpression of rice F-box phloem protein gene OsPP12-A13 confers salinity tolerance in Arabidopsis

Salinity is a serious challenge for agriculture production by limiting the arable land. Rice is a major staple food crop but very sensitive to salt stress. In this study, we used Arabidopsis for the functional characterization of a rice F-box gene LOC_Os04g48270 (OsPP12-A13) under salinity stress. OsPP12-A13 is a nuclear-localized protein that is strongly upregulated under salinity stress in rice and showed the highest expression in the stem, followed by roots and leaves. Two types of transgenic lines for OsPP12-A13 were generated, including constitutive tissue over-expression using the CaMV35S promoter and phloem specific over-expression using the pSUC2 promoter. Both types of transgenic plants showed salinity tolerance at the seedling stage through higher germination percentage and longer root length, as compared to control plants under salt stress in MS medium. Both the transgenic plants also exhibited salt tolerance at the reproductive stage through higher survival rate, plant dry biomass, and seed yield per plant as compared to control plants. Determination of Na+ concentration in leaves, stem and roots of salt-stressed transgenic plants showed that Na+ concentration was less in leaf and stem as compared to roots. The opposite was observed in wild type stressed plants, suggesting that OsPP12-A13 may be involved in Na+ transport from root to leaf. Transgenic plants also displayed less ROS levels and higher activities of peroxidase and glutathione S-transferase along with upregulation of their corresponding genes as compared to control plants which further indicated a role of OsPP12-A13 in maintaining ROS homeostasis under salt stress. Further, the non-significant difference between the transgenic lines obtained from the two vectors highlighted that OsPP12-A13 principally works in the phloem. Taken together, this study showed that OsPP12-A13 improves salt tolerance in rice, possibly by affecting Na+ transport and ROS homeostasis.