RESUMO
Improvement of drought tolerance of crops is a great challenge in conditions of increasing climate change. This report describes that the silencing of the synaptotagmin-5 (OsSYT-5) gene encoding the rice Ca2+ sensing protein with a C2 domain led to a significant improvement of rice tolerance to water deficit stress. Transgenic lines with suppressed expression of the OsSYT-5 gene exhibited an enhanced photosynthetic rate but reduced stomatal conductance and transpiration during water deficit stress. The abscisic acid (ABA) content under both normal and drought conditions was elevated in the leaves of the transgenic rice as compared to the wild type. The silencing of the OsSYT-5 gene affected the expression of several genes associated with ABA-related stress signaling in the transgenic rice plants. In the water deficit experiment, the transgenic lines with a silenced OsSYT-5 gene exhibited symptoms of drought stress seven days later than the wild type. Transgenic lines with suppressed OsSYT-5 gene expression exhibited higher pollen viability and produced more grains compared to the wild type at both normal and drought stress conditions.