An Arabidopsis Nucleoporin NUP85 modulates plant responses to ABA and salt stress.

Yingfang Zhu,Yuting Yang,Kai Tang,Bangshing Wang,Shaojun Xie,Jian-Kang Zhu,Hai Du,Chuan-Chih Hsu,Weiguo Andy Tao,Zhen-Ming Pei

doi:10.1371/journal.pgen.1007124

Abstract

Several nucleoporins in the nuclear pore complex (NPC) have been reported to be involved in abiotic stress responses in plants. However, the molecular mechanism of how NPC regulates abiotic stress responses, especially the expression of stress responsive genes remains poorly understood. From a forward genetics screen using an abiotic stress-responsive luciferase reporter (RD29A-LUC) in the sickle-1 (sic-1) mutant background, we identified a suppressor caused by a mutation in NUCLEOPORIN 85 (NUP85), which exhibited reduced expression of RD29A-LUC in response to ABA and salt stress. Consistently, the ABA and salinity induced expression of several stress responsive genes such as RD29A, COR15A and COR47 was significantly compromised in nup85 mutants and other nucleoporin mutants such as nup160 and hos1. Subsequently, Immunoprecipitation and mass spectrometry analysis revealed that NUP85 is potentially associated with HOS1 and other nucleoporins within the nup107-160 complex, along with several mediator subunits. We further showed that there is a direct physical interaction between MED18 and NUP85. Similar to NUP85 mutations, MED18 mutation was also found to attenuate expression of stress responsive genes. Taken together, we not only revealed the involvement of NUP85 and other nucleoporins in regulating ABA and salt stress responses, but also uncovered a potential relation between NPC and mediator complex in modulating the gene expression in plants.

Highlights

Nucleocytoplasmic transport plays vital roles in eukaryotic systems [1,2]
Mutation in NUCLEOPORIN 85 (NUP85) and other nuclear pore complexes (NPCs) components such as NUP160 and HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES1 (HOS1) resulted in decreased expression of several stress responsive genes
To identify new factors involved in abiotic stress responses, we performed a forward genetics screen using an EMS mutant population generated in the sic-1 mutant background with the stress-inducible proRD29A-LUC reporter gene

Summary

Introduction

Nucleocytoplasmic transport plays vital roles in eukaryotic systems [1,2]. The exchange of macromolecules such as RNAs and proteins is predominantly regulated by highly conserved nuclear pore complexes (NPCs), which consist of multi-nucleoporins (Nups) arranged in distinct sub-complexes [3,4]. NUP160 was shown to be involved in cold stress responses since the knockout of NUP160 impaired cold-induced expression the CBF3-LUC reporter gene and several endogenous genes; and resulted in hypersensitivity to chilling and freezing stresses [8]. Another important NPC component [9], HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES1 (HOS1), which encodes a RING finger E3 ubiquitin ligase, is well-known as a negative regulator in the cold signaling [10]. Only HOS1 was demonstrated to interact with specific chromatin such as the floral repressor FLOWERING LOCUS C (FLC) chromatin to regulate FLC transcription under low temperature [14,15,16]

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