Prof. Sang-Yeol Lee’s team at Gyeongsang National University publishes a paper in 《Molecular Plant》

▸A molecular switch triggered by heat stress: a protein-degrading enzyme transforms into a protein protector

▸Foundational technology secured to enhance plant heat tolerance, expected to contribute to developing heat-tolerant crops to cope with extreme weather

▸A purely homegrown domestic research achievement realized at Gyeongsang National University…demonstrating world-class research prowess

▸Research led by Dr. Ho-Byeong Chae and Dr. Su-Bin Bae at the Institute of Plant Biotechnology, Gyeongsang National University

◐ One protein, two faces—an exquisite, heat-activated survival strategy in plants

The secret to how crops survive scorching summer heat stress without collapsing was hidden within a single protein.

Endowed Chair Prof. Sang-Yeol Lee’s research team at Gyeongsang National University (GNU; President Jin-Hoe Kwon) has, for the first time in the world, elucidated the sophisticated molecular mechanism by which a protein called EMR in plant cells switches its function in response to heat-stress signals from a protein-degrading enzyme to a protein protector. These results were published online on June 3 (KST) in 《Molecular Plant》 (IF: 24.1; ranked 2nd in plant science; top 0.5%), the world’s leading journal in plant science.

◐ “From degrader to guardian—one zinc ion changes its fate”

The protagonist of this study is a protein called EMR. Under normal conditions, EMR resides in the endoplasmic reticulum of plant cells and, as an E3 ubiquitin ligase that tags damaged or unnecessary proteins with ubiquitin for degradation, quietly serves as a cellular janitor.

However, the moment heat stress is applied, EMR begins a remarkable transformation. As a zinc ion (Zn²⁺) that had been held within the protein is released, EMR’s structure changes wholesale. It reassembles from a lone monomer into an oligomeric form, leaves the endoplasmic reticulum for the cytosol, and turns into a molecular chaperone that seizes and protects neighboring proteins that start to aggregate due to heat. It is the instant when a degrader that disposed of damaged proteins turns into a guardian that protects other proteins.

Even more remarkable, all of these transitions occur without complex processes such as synthesizing new proteins or newly activating genes; they are accomplished solely by a conformational change triggered by the release of a single zinc ion. It is an exquisite redox molecular switch, honed by hundreds of millions of years of evolution, that enables immediate crisis response while minimizing energy and time.

◐ “Mechanism of the heat-stress redox molecular switch uncovered through multifaceted experiments”

The team delineated this mechanism step by step. Artificially removing the zinc ion converts EMR into an oligomer and confers chaperone function even without heat stress, whereas supplying zinc restores the oligomer to a monomer and recovers E3 ligase activity. This is direct evidence that it is the presence or absence of the zinc ion—not heat itself—that is the true key determining EMR’s fate.

Furthermore, using confocal microscopy, the team visually confirmed that under heat stress EMR relocates from the endoplasmic reticulum to the cytosol, and they directly demonstrated via in vivo experiments that zinc ions are indeed released within plant cells. They also obtained genetic evidence that mutant plants lacking E3 ligase activity but retaining only chaperone function show heat tolerance equivalent to plants overexpressing wild-type EMR, thereby demonstrating from multiple angles that EMR’s chaperone function plays a central role in plant heat tolerance. Comparative proteomic analysis further revealed that EMR protects ribosomal proteins involved in protein synthesis from heat.

◐ “In the era of climate change, opening a new path to developing heat-tolerant crops”

This study is noteworthy not only as a basic-science achievement but also for presenting tangible potential for agricultural applications. As extreme heat events become more frequent due to climate change and damage to heat-sensitive crops rises worldwide, the discovery of key proteins like EMR that enhance heat tolerance and the elucidation of their mechanisms can serve as direct foundational technology for developing heat-tolerant crops.

Prof. Sang-Yeol Lee emphasized, “This study is the first to elucidate a sophisticated redox molecular switch mechanism by which plants dynamically convert the structure and function of a protein under the extreme condition of heat stress,” adding, “The discovery that a single protein can immediately perform two completely different functions depending on environmental signals is a highly innovative achievement in plant life science.” The team stated, “We plan to continue pursuing the development of heat-tolerant crops by leveraging key proteins that confer resistance to heat stress.”

This research was supported by grants from the National Research Foundation of Korea and the Plant Circadian Rhythm Research Center (SRC; Director Prof. Oe-Yeon Kim). The paper’s title is “Heat shock-induced zinc efflux repurposes Arabidopsis E3 ligase EMR as a molecular chaperone.”

In particular, these results are a purely homegrown research achievement realized entirely at Gyeongsang National University, once again demonstrating that the university’s researchers possess world-class research capabilities.

◐ Research Team Introduction

Professor Sang Yeol Lee, who supervised the paper, said, "Dr. Ho Byeong Chae and Dr. Subin Bae, who led the study, demonstrated passion and outstanding experimental capabilities by constantly challenging difficult research questions," adding, "It was thanks to the close collaboration and creative thinking of the two researchers that such world-class results were achieved."

Professor Sang Yeol Lee's team focuses on environmental stress caused by climate change and the mechanisms of plant stress resistance, and, starting with a 2004 paper in 《Cell》, has published numerous papers in leading journals such as 《Science》, 《Molecular Plant》, 《Nature Plants》, 《Nature Communication》, and 《U.S. Royal Society Journal (PNAS)》.

As a full member of the Korean Academy of Science and Technology, Professor Sang Yeol Lee served as Director of Gyeongsang National University's 'Systems Synthesis Agri-Life Biotechnology Project Group' (2011–2020) and as President of the Korean Society for Molecular and Cellular Biology (2015), and he is currently actively conducting research as a Distinguished Professor at Gyeongsang National University.

ㅇ Photo description:

Dr. Ho Byeong Chae and Dr. Subin Bae of the Plant Biotechnology Research Institute, Gyeongsang National University, and Distinguished Professor Sang Yeol Lee

ㅇ For inquiries: Professor Sang Yeol Lee, Gyeongsang National University 055-772-1351

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