SSR1 is a vital regulator in plant mitochondrial iron-sulfur biosynthesis

• Published in: bioRxiv
• Main Authors: Feng, Xuanjun, Han, Huiling, Bonea, Diana, Liu, Jie, Wenhan Ying, Cai, Yuanyuan, Zhang, Min, Lu, Yanli, Zhao, Rongmin, Hua, Xuejun
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 10.03.2021; Cold Spring Harbor Laboratory
• Edition: 1.1
• Subjects: Amino acid substitution; Biosynthesis; Enzymatic activity; Iron-sulfur proteins; Membrane potential; Mitochondria; Phenotypes; Plant Biology; Sulfur; Sulfur proteins
• ISSN: 2692-8205; 2692-8205
• DOI: 10.1101/2021.03.09.434627

Abstract The Arabidopsis SHORT AND SWOLLEN ROOT1 (SSR1) gene encodes a mitochondrial TPR domain-containing protein and was previously reported to function in maintaining mitochondria function. In a screen for suppressors of the short-root phenotype of the loss-of-function mutant ssr1-2, two mutations, sus1 and sus2 (suppressor of ssr1-2), were isolated. sus1 and sus2 result from G87D and T55M single amino acid substitution in HSCA2 (At5g09590) and ISU1 (At4g22220), both of which are core components in iron-sulfur cluster biosynthesis pathway in mitochondria (ISC). We here demonstrated that SSR1 displayed a strong chaperone-like activity and was able to enhance the binding of HSCA2 to ISU1, an essential step for the normal operation of ISC machinery. Accordingly, the enzymatic activities of several iron-sulfur proteins, the mitochondrial membrane potential and ATP content are reduced in ssr1-2. Interestingly, SSR1 appears to exist only in plant lineages, possibly conferring adaptive advantages on plant ISC machinery to environment.