Functional changes of OsTrxm from reductase to molecular chaperone under heat shock stress

Ho Byoung Chae; Young Jun Jung; Seol Ki Paeng; Hyun Suk Jung; Sang Yeol Lee; Jung Ro Lee

doi:10.1016/j.plaphy.2023.108005

Functional changes of OsTrxm from reductase to molecular chaperone under heat shock stress

Plant Physiol Biochem. 2023 Oct:203:108005. doi: 10.1016/j.plaphy.2023.108005. Epub 2023 Sep 7.

Authors

Ho Byoung Chae¹, Young Jun Jung², Seol Ki Paeng¹, Hyun Suk Jung³, Sang Yeol Lee¹, Jung Ro Lee⁴

Affiliations

¹ Division of Applied Life Sciences (BK21(+)), PMBBRC, and Plant Biological Rhythm Research Center, Gyeongsang National University, Jinju, 52828, South Korea.
² National Institute of Ecology, 1210 Geumgang-ro, Maseo-myeon, Seocheon-gun, 33657, Republic of Korea.
³ Department of Biochemistry, College of Natural Sciences, Kangwon National University, Chuncheon, 24341, Republic of Korea.
⁴ National Institute of Ecology, 1210 Geumgang-ro, Maseo-myeon, Seocheon-gun, 33657, Republic of Korea. Electronic address: leejr73@nie.re.kr.

PMID: 37776672
DOI: 10.1016/j.plaphy.2023.108005

Abstract

Ubiquitous disulfide reductases, thioredoxins (Trxs), function in the redox balance of all living organisms. Although the roles of the rice (Oryza sativa) Trx m-type isoform (OsTrxm) in chloroplast development have been already published, biochemical and molecular functions of OsTrxm remain to be elucidated for decades. The OsTrxm and its two conserved active cysteine mutant (OsTrxm C95S/C98S, referred to as OsTrxmC/S) proteins in Arabidopsis thaliana were overexpressed to characterize in vivo roles of active cysteines of OsTrxm. Interestingly, the OsTrxm overexpressed variant plants were resistant to heat shock treatment. Especially OsTrxmC/S with higher molecular weight (HMW) complexes showed higher heat tolerance than OsTrxm with lower molecular weight (LMW) structure in Arabidopsis thaliana. To confirm the importance of active cysteines on structural changes under heat stress, OsTrxm and OsTrxmC/S proteins were bacterially expressed and isolated. This study found that two proteins have various structures ranging from LMW to HMW complexes and have potential functions as a disulfide reductase and a molecular chaperone, which has never been reported anywhere. The function of molecular chaperone predominated in the HMW complexes, whereas the disulfide reductase function was observed in LMW forms. These results suggest that the active cysteines of OsTrxm play a critical role in protein structural change as well as heat tolerance in plants.

Keywords: Active cysteine; Higher molecular weight (HMW); Lower molecular weight (LMW); Molecular chaperone; Oryza sativa Trx m-type (OsTrxm); Reductase.