Heterologous Expression of Two Jatropha Aquaporins Imparts Drought and Salt Tolerance and Improves Seed Viability in Transgenic Arabidopsis thaliana

Drought and high salinity are environmental conditions that cause adverse effects on the growth and productivity of crops. Aquaporins are small integral membrane proteins that belong to the family of the major intrinsic proteins (MIPs), with members in animals, plants and microbes, where they facilitate the transport of water and/or small neutral solutes thereby affecting water balance. In this study we characterized two aquaporin genes namely, plasma membrane intrinsic protein (PIP2; 7) and tonoplast intrinsic protein TIP1; 3 from Jatropha curcas that are localised to the plasma membrane and vacuole respectively. Transgenic Arabidopsis thaliana lines over-expressing JcPIP2; 7 and JcTIP1; 3 under a constitutive promoter show improved germination under high salt and mannitol compared to control seeds. These transgenic plants also show increased root length under abiotic stress conditions compared to wild type Col-0 plants. Transgenic lines exposed to drought conditions by withholding water for 20 days, were able to withstand water stress and attained normal growth after re-watering unlike control plants which could not survive. Transgenic lines also had better seed yield than control under salt stress. Importantly, seed viability of transgenic plants grown under high salt concentration was 35%-45% compared to less than 5% for control seeds obtained from plants growing under salt stress. The effect of JcPIP2; 7 and JcTIP1; 3 on improving germination and seed viability in drought and salinity make these important candidates for genetic manipulation of plants for growth in saline soils.