Overexpressing GH3.1 and GH3.1L reduces susceptibility to Xanthomonas citri subsp. citri by repressing auxin signaling in citrus (Citrus sinensis Osbeck)

• Published in: PloS one Vol. 14; no. 12; p. e0220017
• Main Authors: Zou, Xiuping, Long, Junhong, Zhao, Ke, Peng, Aihong, Chen, Min, Long, Qin, He, Yongrui, Chen, Shanchun
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 12.12.2019; Public Library of Science (PLoS)
• Subjects: Abscisic acid; Acetic acid; Amino acids; Analysis; Biology and Life Sciences; Biosynthesis; Canker; Cell division; Cellular signal transduction; Citrus; Citrus canker; Citrus fruits; Citrus sinensis; Citrus sinensis - genetics; Citrus sinensis - immunology; Citrus sinensis - microbiology; Conjugation; Cytokinins; Disease resistance; Disease Resistance - genetics; Disease Resistance - immunology; Dwarfism; Engineering and Technology; Ethylene; Gene expression; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes; Genetic engineering; Genetically modified plants; Genomes; Genomics; Homeostasis; Hormones; Indoleacetic acid; Indoleacetic Acids - antagonists & inhibitors; Indoleacetic Acids - metabolism; Jasmonic acid; Leaves; Organic acids; Pathogens; Phenols (Class of compounds); Plant diseases; Plant Diseases - genetics; Plant Diseases - immunology; Plant Diseases - microbiology; Plant growth; Plant hormones; Plant pathology; Plant Proteins - genetics; Plant Proteins - metabolism; Plant resistance; Plants, Genetically Modified - genetics; Plants, Genetically Modified - immunology; Plants, Genetically Modified - microbiology; Proteins; Research and Analysis Methods; RNA polymerase; Salicylic acid; Signal transduction; Signaling; Transgenic plants; Xanthomonas - immunology; Xanthomonas - pathogenicity; Xanthomonas citri; Zeatin; China
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0220017

The auxin early response gene Gretchen Hagen3 (GH3) plays dual roles in plant development and responses to biotic or abiotic stress. It functions in regulating hormone homeostasis through the conjugation of free auxin to amino acids. In citrus, GH3.1 and GH3.1L play important roles in responding to Xanthomonas citri subsp. citri (Xcc). Here, in Wanjingcheng orange (Citrus sinensis Osbeck), the overexpression of CsGH3.1 and CsGH3.1L caused increased branching and drooping dwarfism, as well as smaller, thinner and upward curling leaves compared with wild-type. Hormone determinations showed that overexpressing CsGH3.1 and CsGH3.1L decreased the free auxin contents and accelerated the Xcc-induced decline of free auxin levels in transgenic plants. A resistance analysis showed that transgenic plants had reduced susceptibility to citrus canker, and a transcriptomic analysis revealed that hormone signal transduction-related pathways were significantly affected by the overexpression of CsGH3.1 and CsGH3.1L. A MapMan analysis further showed that overexpressing either of these two genes significantly downregulated the expression levels of the annotated auxin/indole-3-acetic acid family genes and significantly upregulated biotic stress-related functions and pathways. Salicylic acid, jasmonic acid, abscisic acid, ethylene and zeatin levels in transgenic plants displayed obvious changes compared with wild-type. In particular, the salicylic acid and ethylene levels involved in plant resistance responses markedly increased in transgenic plants. Thus, the overexpression of CsGH3.1 and CsGH3.1L reduces plant susceptibility to citrus canker by repressing auxin signaling and enhancing defense responses. Our study demonstrates auxin homeostasis' potential in engineering disease resistance in citrus.