Emergence of isochorismate- based salicylic acid biosynthesis within Brassicales

• 成果类型: Article
• 署名作者: Hong, Kunqi; Nakano, Masahito; Tang, Ying; Jeanguenin, Linda; Kang, Wenshang; Wang, Yongliang; Zuo, Lu; Li, Pengyue; He, Jingjng; Jiang, Wanqing; Huang, Ruidong; Matsui, Hidenori; Wang, Yiming; Nakagami, Hirofumi; Li, Bo; Li, Xia; Xie, Kabin; Fukushima, Kenji; Guo, Liang; Han, Xiaowei; Katagiri, Fumiaki; Hattori, Motoyuki; Tsuda, Kenichi
• 署名单位: Huazhong Agricultural University; Hubei Hongshan Laboratory; University of Minnesota System; University of Minnesota Twin Cities; Hubei Hongshan Laboratory; Huazhong Agricultural University; RIKEN; Okayama University; Nanjing Agricultural University; Max Planck Society; Research Organization of Information & Systems (ROIS); National Institute of Genetics (NIG) - Japan; Fudan University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9863
• DOI: 10.1073/pnas.2506170122
• 发表日期: 2025-07-22
• 关键词: genome duplications; disease resistance; plant-growth; arabidopsis; gene; synthase; phenylalanine; EVOLUTION; mutants; HISTORY

摘要

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 of IC-based SA biosynthesis.