OsWRKY62 and OsWRKY76 Interact with Importin α1s for Negative Regulation of Defensive Responses in Rice Nucleus

Xiaohui Xu; Han Wang; Jiqin Liu; Shuying Han; Miaomiao Lin; Zejian Guo; Xujun Chen

doi:10.1186/s12284-022-00558-4

OsWRKY62 and OsWRKY76 Interact with Importin α1s for Negative Regulation of Defensive Responses in Rice Nucleus

Rice (N Y). 2022 Feb 20;15(1):12. doi: 10.1186/s12284-022-00558-4.

Authors

Xiaohui Xu^{1

2}, Han Wang¹, Jiqin Liu¹, Shuying Han¹, Miaomiao Lin¹, Zejian Guo¹, Xujun Chen³

Affiliations

¹ Key Laboratory of Pest Monitoring and Green Management, MOA, Joint Laboratory for International Cooperation in Crop Molecular Breeding; Department of Plant Pathology, China Agricultural University, Beijing, 100193, China.
² College of Modern Science and Technology, China Jiliang University, Hangzhou, 310018, China.
³ Key Laboratory of Pest Monitoring and Green Management, MOA, Joint Laboratory for International Cooperation in Crop Molecular Breeding; Department of Plant Pathology, China Agricultural University, Beijing, 100193, China. chenxj@cau.edu.cn.

Abstract

Background OsWRKY62 and OsWRKY76, two close members of WRKY transcription factors, function together as transcriptional repressors. OsWRKY62 is predominantly localized in the cytosol. What are the regulatory factors for OsWRKY62 nuclear translocation? Results In this study, we characterized the interaction of OsWRKY62 and OsWRKY76 with rice importin, OsIMα1a and OsIMα1b, for nuclear translocation. Chimeric OsWRKY62.1-GFP, which is predominantly localized in the cytoplasm, was translocated to the nucleus of Nicotiana benthamiana leaf cells in the presence of OsIMα1a or OsIMαΔIBB1a lacking the auto-inhibitory importin β-binding domain. OsIMαΔIBB1a interacted with the WRKY domain of OsWRKY62.1, which has specific bipartite positively charged concatenated amino acids functioning as a nuclear localization signal (NLS). Similarly, we found that OsIMαΔIBB1a interacted with the AvrPib effector of rice blast fungus Magnaporthe oryzae, which contains a scattered distribution of positively charged amino acids. Furthermore, we identified a nuclear export signal (NES) in OsWRKY62.1 that inhibited nuclear transportation. Overexpression of OsIMα1a or OsIMα1b enhanced resistance to M. oryzae, whereas knockout mutants decreased resistance to the pathogen. However, overexpressing both OsIMα1a and OsWRKY62.1 were slightly more susceptible to M. oryzae than OsWRKY62.1 alone. Ectopic overexpression of OsWRKY62.1-NES fused gene compromised the enhanced susceptibility of OsWRKY62.1 to M. oryzae. Conclusion These results revealed the existence of NLS and NES in OsWRKY62. OsWRKY62, OsWRKY76, and AvrPib effector translocate to nucleus in association with importin α1s through new types of nuclear localization signals for negatively regulating defense responses.

Keywords: AvrPib; Importin α; Magnaporthe oryzae; Nuclear localization signal; Oryza sativa; WRKY.

Abstract

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