Overexpression of a GIPC glycosyltransferase gene, OsGMT1, suppresses plant immunity and delays heading time in rice

• Published in: Plant science (Limerick) 2023-06, Vol.331, p.111674-111674, Article 111674
• Main Authors: Lin, Yuelong, Zhu, Yongsheng, Wang, Lanning, Zheng, Yanmei, Xie, Yunjie, Cai, Qiuhua, He, Wei, Xie, Hongguang, Liu, Haitao, Wang, Yingheng, Cui, Lili, Wei, Yidong, Xie, Huaan, Zhang, Jianfu
• Format: Article
• Language: English
• Subjects: Arabidopsis - metabolism; Calcein AM release assay; Gene Expression Regulation, Plant; GIPC; Glycosyltransferases - genetics; Glycosyltransferases - metabolism; Hydrogen Peroxide - metabolism; MoNLP1; Oryza - physiology; OsGMT1; OsHAP5 gene family; Plant Immunity - genetics; Plant Proteins - genetics; Plant Proteins - metabolism; Plants - metabolism; Plants, Genetically Modified - genetics; Plants, Genetically Modified - metabolism; Rice blast; Saccharomyces cerevisiae - metabolism; Sphingolipids - metabolism
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2023.111674

Glycosylinositol phosphorylceramides (GIPCs) are the major sphingolipids in the plant plasma membrane. In Arabidopsis, mutations of genes involved in the synthesis of GIPCs affect many physiological aspects of plants, including growth, pollen fertility, defense, and stress signaling. Loss of function of the GIPC MANNOSYL-TRANSFERASE1 (AtGMT1) results in GIPC misglycosylation and induces plant immune responses accompanied by a severely dwarfed phenotype, thus indicating that GIPCs play important roles in plant immunity. Here, we investigated the enzymatic activity and phenotypes of transgenic lines of OsGMT1, the ortholog of AtGMT1. Sphingolipidomic analysis indicated that OsGMT1 retained the enzymatic activity of GIPC hexose (Hex) glycosylation, but the knockout lines did not accumulate H2O2. In contrast, the OsGMT1 overexpression lines showed significant down-regulation of several defense-associated or cell wall synthesis-associated genes, and enhanced sensitivity to rice blast. Furthermore, we first demonstrated the sensitivity of rice cells to MoNLP1 protein through calcein AM release assays using rice protoplasts, thus legitimizing the presence of MoNLPs in rice blast fungus. In addition, yeast two-hybrid screens using OsGMT1 as bait revealed that OsGMT1 may regulate heading time through the OsHAP5C signaling pathway. Together, our findings suggested clear physiological functional differentiation of GMT1 orthologs between rice and Arabidopsis. •Loss of function of OsGMT1, the ortholog of AtGMT1, did not result in accumulation of peroxidase and H2O2 in homozygous knockout transgenic rice plants, thus indicating functional differentiation of GMT1 orthologs between rice and Arabidopsis.•Sphingolipidomic analysis of OsGMT1 overexpression lines indicated that OsGMT1 retained GIPC Hex glycosylation enzymatic activity.•The sensitivity of monocot rice cells to MoNLP1 toxin secreted by Magnaporthe grisea was demonstrated through calcein AM release assays using rice protoplasts.•OsGMT1 may regulate heading time through the OsHAP5C signaling pathway.