J Integr Plant Biol. ›› 2016, Vol. 58 ›› Issue (7): 669-678.DOI: 10.1111/jipb.12448

Special Issue: Sexual Reproductions

• Plant Reproduction Biology • Previous Articles     Next Articles

The Arabidopsis CROWDED NUCLEI genes regulate seed germination by modulating degradation of ABI5 protein

Wenming Zhao1,2†, Chunmei Guan1, Jian Feng1,2‡, Yan Liang, Ni Zhan1,2, Jianru Zuo1 and Bo Ren1*   

  1. 1State Key Laboratory of Plant Genomics and National Plant Gene Research Center, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
    2University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2015-09-08 Accepted:2015-11-10 Published:2015-11-13
  • About author:Current address: Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
    Current address: John Innes Centre, Norwich NR4 7UH, United Kingdom,
    §Current address: Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
    *Correspondence: E-mail: bren@genetics.ac.cn

Abstract:

In Arabidopsis, the phytohormone abscisic acid (ABA) plays a vital role in inhibiting seed germination and in post-germination seedling establishment. In the ABA signaling pathway, ABI5, a basic Leu zipper transcription factor, has important functions in the regulation of seed germination. ABI5 protein localizes in nuclear bodies, along with AFP, COP1, and SIZ1, and was degraded through the 26S proteasome pathway. However, the mechanisms of ABI5 nuclear body formation and ABI5 protein degradation remain obscure. In this study, we found that the Arabidopsis CROWDED NUCLEI (CRWN) proteins, predicted nuclear matrix proteins essential for maintenance of nuclear morphology, also participate in ABA-controlled seed germination by regulating the degradation of ABI5 protein. During seed germination, the crwn mutants are hypersensitive to ABA and have higher levels of ABI5 protein compared to wild type. Genetic analysis suggested that CRWNs act upstream of ABI5. The observation that CRWN3 colocalizes with ABI5 in nuclear bodies indicates that CRWNs might participate in ABI5 protein degradation in nuclear bodies. Moreover, we revealed that the extreme C-terminal of CRWN3 protein is necessary for its function in the response to ABA in germination. Our results suggested important roles of CRWNs in ABI5 nuclear body organization and ABI5 protein degradation during seed germination.

Key words: ABI5, Arabidopsis, CROWDED NUCLEI, germination, nuclear body

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