Molecular Characterization of SEC62 in ER-Phagy in Arabidopsis
Shuai Hua and Liwen Jianga,b aSchool of Life Sciences, Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China; bShenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China
Protein folding processes can be severely affected under stress conditions. Large amount of misfolded proteins accumulates in the endoplasmic reticulum (ER) which in turn overwhelming the protein folding machinery. This leads to the ER stress and triggers unfolded protein responses (UPR). Multiple mechanisms such as endoplasmic-reticulum-associated protein degradation (ERAD) have been proposed to relieve the ER stress. Resolution of the ER stress must be followed by a recovery phase that re-establishes the physiological ER homeostasis including recovery of ER morphology to its pre-stress levels. Recent studies suggested that the selective removal of damaged and excessive ER membrane was dependent on selective autophagy termed ER-phagy. However, the molecular mechanisms for plant ER-phagy remains elusive. Here we aim to characterize the function of an ER transmembrane located protein SEC62 in plant ER-phagy using a combination of cellular, molecular and genetic approaches. Upon ER stress, SEC62 may serve as a receptor for ATG8 recognition and hence promoting delivery of selected ER domains to autophagosome for clearance. To study the potential role of SEC62 in plant ER-phagy, transgenic Arabidopsis plants co-expressing YFP-SEC62 and mCherry-ATG8e were generated. Subcellular localization of SEC62 in transgenic Arabidopsis plants was determined under normal and ER stress conditions. Preliminary results showed that YFP-SEC62 localizes to the ER network under normal condition. Interestingly, YFP-SEC62 was found to be enriched in subdomains of the ER and co-localized with ATG8e-positive ring-like structures under ER stress condition. Immunogold-TEM (transmission electron microscopy) will be used to study the SEC62-enriched domain at the ultra-structural level. In addition, we will also screen and generate T-DNA insertional knockout mutant and artificial-microRNAi knockdown mutants of sec62 for further functional study. Preliminary data showed that sec62 mutants exhibits dwarfed and reduced fertilization phenotypes. Further studies will be performed to assay the sensitivity of sec62 mutant during ER stress. An update on the research progress will be presented.
Supported by grants from the Research Grants Council of Hong Kong (CUHK14130716, CUHK2/CRF/11G, C4011-14R, C4012-16E and AoE/M-05/12).
Credits: None available.
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