RanBP1-1 Is Involved in the Induction of Disease Resistance Via Regulation of Nuclear-Cytoplasmic Transport of Small GTPase Ran

Plant cells enhance the tolerances to abiotic and biotic stresses via recognition of the stress, activation and nuclear import of signaling factors, up-regulation of defense genes, nuclear export of mRNA and translation of defense proteins. Nuclear pore-mediated transports should play critical roles in these processes, however, the regulatory mechanisms of nuclear-cytoplasmic transport during stress responses are largely unknown. In this study, a regulator of nuclear export of RNA and proteins, NbRanBP1-1 (Ran-binding protein1-1), was identified as an essential gene for the resistance of to potato blight pathogen . -silenced plants showed delayed accumulation of capsidiol, a sesquiterpenoid phytoalexin, in response to elicitor treatment, and reduced resistance to . Abnormal accumulation of mRNA was observed in -silenced plants, indicating that NbRanBP1-1 is involved in the nuclear export of mRNA. In -silenced plants, elicitor-induced expression of defense genes, and , was not affected in the early stage of defense induction, but the accumulation of NbWIPK protein was reduced. Nuclear export of the small G-protein NbRan1a was activated during the induction of plant defense, whereas this process was compromised in -silenced plants. Silencing of genes encoding the nuclear pore proteins, and , also caused abnormal nuclear accumulation of mRNA, defects in the nuclear export of NbRan1a, and reduced production of capsidiol, resulting in decreased resistance to . These results suggest that nuclear export of NbRan is a key event for defense induction in , and both RanBP1-1 and nucleoporins play important roles in the process.