Induction of OsVP1 transcription factor encoding gene by droughtstress and ABA at reproductive stage of rice

Drought stress is a major constraint to rice (Oryza sativa) production, particularly at the reproductive stage. One of the most important reasons for the effect of drought is the inhibition of peduncle elongation, resulting in panicle retention inside the flag leaf sheath so that the unexserted spikelets remain sterile. This research was focused on studying expression patterns of OsVP1 transcription factor encoding gene during drought-stress and abscisic acid -induced growth arrest at peduncles. The expression of OsVP1 gene was significantly up-regulated during the growth arrest induced by either drought stress or ABA and down-regulated again by re-watering or ABA removal and restoring the growth in the peduncles. OsVP1 transcripts were mostly observed in the young immature tissues and the expression levels were decreased from division zone to maturation zone; however it was always increased by drought stress. In the divisional zone of the peduncle, transcripts of this gene was observed in almost all cells and accumulated more in the nuclei. Therefore, based on the achieved results and that OsVP1 encodes a transcription factor, this gene probably affects the expression of many other genes, directly or indirectly, involved in drought stress and ABA induced growth arrest.