Abstract
The transport of proteins to and from the nucleus is necessary for many cellular processes and is one of the ways plants respond to developmental signals and environmental stresses. Nucleocytoplasmic trafficking of proteins is mediated by the nuclear transport receptor (NTR). Although NTR has been extensively studied in humans and Arabidopsis, it has rarely been identified and functionally characterized in rice. In this study, we identified exportin 1 in rice (OsXPO1) as a nuclear export receptor. OsXPO1 shares high protein identity with its functional homologs in Arabidopsis and other organisms. OsXPO1 localized to both the nucleus and the cytoplasm, directly interacted with the small GTPases OsRAN1 and OsRAN2 in the nucleus, and mediated their nuclear export. Loss-of-function osxpo1 mutations were lethal at the seedling stage. Suppression of OsXPO1 expression in RNA interference lines produced multifaceted developmental defects, including arrested growth, premature senescence, abnormal inflorescence, and brown and mouth-opened spikelets. Overexpression of OsXPO1 in rice reduced plant height and seed-setting rate, but increased plant tolerance in response to PEG-mimicked drought stress and salt stress. These results indicate that OsXPO1 is a nuclear export receptor and acts in regulating plant development and abiotic stress responses.
