{"title":"Emergence of isochorismate-based salicylic acid biosynthesis within Brassicales.","authors":"Kunqi Hong, Masahito Nakano, Ying Tang, Linda Jeanguenin, Wenshang Kang, Yongliang Wang, Lu Zuo, Pengyue Li, Jingjng He, Wanqing Jiang, Ruidong Huang, Hidenori Matsui, Yiming Wang, Hirofumi Nakagami, Bo Li, Xia Li, Kabin Xie, Kenji Fukushima, Liang Guo, Xiaowei Han, Fumiaki Katagiri, Motoyuki Hattori, Kenichi Tsuda","doi":"10.1073/pnas.2506170122","DOIUrl":null,"url":null,"abstract":"<p><p>Salicylic acid (SA) is a major defense phytohormone. In <i>Arabidopsis thaliana</i>, the isochorismate (IC) pathway is the primary route for pathogen-induced SA biosynthesis. First, the IC synthase (ICS) catalyzes the isomerization of chorismate to IC in chloroplasts. Second, the chloroplast-localized MATE transporter EDS5 appears to transport IC from chloroplasts to the cytosol. Cytosolic IC is then further converted to SA via the GH3 amino acid-conjugating enzyme PBS3. While this pathway is genetically well-characterized in <i>A. thaliana</i>, its evolutionary origin and conservation remain controversial. In this study, through comprehensive phylogenetic, structural, and functional analyses, we demonstrate that the IC pathway emerged within the Brassicales order in a time span between the divergence of <i>Carica papaya</i> and <i>Capparis spinosa</i>. The evolution of the IC pathway was driven by three key adaptations during the time span: 1) enhancement of ICS activity, 2) neofunctionalization of <i>EDS5</i> after duplication of its ancestral gene, and 3) evolution of a <i>PBS3</i>, whose activity is specialized for glutamate-conjugation to IC. Structural modeling and functional assays reveal that an enhanced salt bridge network in ICS enhanced its activity. One of the duplicated genes, EDS5, acquired key amino acid substitutions in the C-lobe, which contributed to the <i>EDS5</i> neofunctionalization. In addition, the functional <i>PBS3</i> clade, including <i>A. thaliana PBS3</i>, is restricted to a Brassicales clade. Taken together, this study addresses the evolutionary trajectory of IC-based SA biosynthesis.</p>","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"122 29","pages":"e2506170122"},"PeriodicalIF":9.4000,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Proceedings of the National Academy of Sciences of the United States of America","FirstCategoryId":"103","ListUrlMain":"https://doi.org/10.1073/pnas.2506170122","RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/7/17 0:00:00","PubModel":"Epub","JCR":"Q1","JCRName":"MULTIDISCIPLINARY SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Salicylic acid (SA) is a major defense phytohormone. In Arabidopsis thaliana, the isochorismate (IC) pathway is the primary route for pathogen-induced SA biosynthesis. First, the IC synthase (ICS) catalyzes the isomerization of chorismate to IC in chloroplasts. Second, the chloroplast-localized MATE transporter EDS5 appears to transport IC from chloroplasts to the cytosol. Cytosolic IC is then further converted to SA via the GH3 amino acid-conjugating enzyme PBS3. While this pathway is genetically well-characterized in A. thaliana, its evolutionary origin and conservation remain controversial. In this study, through comprehensive phylogenetic, structural, and functional analyses, we demonstrate that the IC pathway emerged within the Brassicales order in a time span between the divergence of Carica papaya and Capparis spinosa. The evolution of the IC pathway was driven by three key adaptations during the time span: 1) enhancement of ICS activity, 2) neofunctionalization of EDS5 after duplication of its ancestral gene, and 3) evolution of a PBS3, whose activity is specialized for glutamate-conjugation to IC. Structural modeling and functional assays reveal that an enhanced salt bridge network in ICS enhanced its activity. One of the duplicated genes, EDS5, acquired key amino acid substitutions in the C-lobe, which contributed to the EDS5 neofunctionalization. In addition, the functional PBS3 clade, including A. thaliana PBS3, is restricted to a Brassicales clade. Taken together, this study addresses the evolutionary trajectory of IC-based SA biosynthesis.
期刊介绍:
The Proceedings of the National Academy of Sciences (PNAS), a peer-reviewed journal of the National Academy of Sciences (NAS), serves as an authoritative source for high-impact, original research across the biological, physical, and social sciences. With a global scope, the journal welcomes submissions from researchers worldwide, making it an inclusive platform for advancing scientific knowledge.