J Integr Plant Biol. ›› 2020, Vol. 62 ›› Issue (9): 1399-1417.DOI: 10.1111/jipb.13005

• Cell and Developmental Biology • Previous Articles     Next Articles

SINAT E3 ligases regulate the stability of the ESCRT component FREE1 in response to iron deficiency in plants

Zhidan Xiao1† , Chao Yang1† , Chuanliang Liu1 , Lianming Yang1 , Shuhong Yang1 , Jun Zhou2 , Faqiang Li3 , Liwen Jiang4 , Shi Xiao5 , Caiji Gao1 * and Wenjin Shen1 *   

  1. 1Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou 510631, China
    2MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China
    3College of Life Sciences, South China Agricultural University, Guangzhou 510642, China
    4School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
    5State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China

    These authors contributed equally to this work.
    *Correspondences: Caiji Gao (gaocaiji@m.scnu.edu.cn, Dr. Gao is fully responsible for the distribution of all materials associated with this article); Wenjin Shen (shenwenjin@m.scnu.edu.cn)
  • Received:2020-08-06 Accepted:2020-08-12 Online:2020-08-12 Published:2020-09-01

Abstract:

The endosomal sorting complex required for transport (ESCRT) machinery is an ancient, evolutionarily conserved membrane remodeling complex that is essential for multivesicular body (MVB) biogenesis in eukaryotes. FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING 1 (FREE1), which was previously identified as a plant‐specific ESCRT component, modulates MVB‐mediated endosomal sorting and autophagic degradation. Although the basic cellular functions of FREE1 as an ESCRT component have been described, the regulators that control FREE1 turnover remain unknown. Here, we analyzed how FREE1 homeostasis is mediated by the RING‐finger E3 ubiquitin ligases, SINA of Arabidopsis thaliana (SINATs), in response to iron deficiency. Under iron‐deficient growth conditions, SINAT1‐4 were induced and ubiquitinated FREE1, thereby promoting its degradation and relieving the repressive effect of FREE1 on iron absorption. By contrast, SINAT5, another SINAT member that lacks ubiquitin ligase activity due to the absence of the RING domain, functions as a protector protein which stabilizes FREE1. Collectively, our findings uncover a hitherto unknown mechanism of homeostatic regulation of FREE1, and demonstrate a unique regulatory SINAT–FREE1 module that subtly regulates plant response to iron deficiency stress.

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