Disulfide reductase activity of thioredoxin-h2 imparts cold tolerance in Arabidopsis

Many thioredoxin-h (Trx-h) proteins, cytosolic isotypes of Trxs, have been functionally characterized in plants; however, the physiological function of Arabidopsis Trx-h2, which harbors two active site cysteine (Cys) residues and an N-terminal extension peptide containing a fatty acid acylation site, remains unclear. In this study, we investigated the physiological function of Trx-h2 by performing several abiotic stress treatments using trx-h1-3 knockout mutant lines, and found that the reductase function of Trx-h2 is critical for cold resistance in Arabidopsis. Plants overexpressing Trx-h2 in the trx-h2 mutant background (Trx-h2(OE)/trx-h2) showed strong cold tolerant phenotypes compared with Col-0 (wild type) and trx-h2 mutant plants. By contrast, Trx-h2(C/S)(OE)/ trx-h2 plants expressing a variant Trx-h2 protein, in which both active site Cys residues were substituted by serine (Ser) residues, showed high cold sensitivity, similar to trx-h2 plants. Moreover, cold-responsive (COR) genes were highly up-regulated in Trxh2(OE)/trx-h2 plants but not in trx-h2 and Trx-h2(C/S)(OE)/trx-h2 plants under cold conditions. These results explicitly suggest that the cytosolic Trx-h2 protein relays the external cold stress signal to downstream cold defense signaling cascades through its protein disulfide reductase function. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

The study investigates the physiological function of Arabidopsis Trx-h2 in cold resistance, demonstrating that the reductase function of Trx-h2 is critical for cold resistance. Overexpressing Trx-h2 enhances cold tolerance in plants, while a variant Trx-h2 protein with substituted active site residues shows increased cold sensitivity. Cold-responsive genes are highly up-regulated in Trx-h2 overexpressing plants under cold conditions, indicating the role of cytosolic Trx-h2 protein in transmitting cold stress signals for cold defense.