GDSL lipases modulate immunity through lipid homeostasis in rice

PLoS Pathog. 2017 Nov 13;13(11):e1006724. doi: 10.1371/journal.ppat.1006724. eCollection 2017 Nov.

Abstract

Lipids and lipid metabolites play important roles in plant-microbe interactions. Despite the extensive studies of lipases in lipid homeostasis and seed oil biosynthesis, the involvement of lipases in plant immunity remains largely unknown. In particular, GDSL esterases/lipases, characterized by the conserved GDSL motif, are a subfamily of lipolytic enzymes with broad substrate specificity. Here, we functionally identified two GDSL lipases, OsGLIP1 and OsGLIP2, in rice immune responses. Expression of OsGLIP1 and OsGLIP2 was suppressed by pathogen infection and salicylic acid (SA) treatment. OsGLIP1 was mainly expressed in leaf and leaf sheath, while OsGLIP2 showed high expression in elongating internodes. Biochemical assay demonstrated that OsGLIP1 and OsGLIP2 are functional lipases that could hydrolyze lipid substrates. Simultaneous down-regulation of OsGLIP1 and OsGLIP2 increased plant resistance to both bacterial and fungal pathogens, whereas disease resistance in OsGLIP1 and OsGLIP2 overexpression plants was significantly compromised, suggesting that both genes act as negative regulators of disease resistance. OsGLIP1 and OsGLIP2 proteins mainly localize to lipid droplets and the endoplasmic reticulum (ER) membrane. The proper cellular localization of OsGLIP proteins is indispensable for their functions in immunity. Comprehensive lipid profiling analysis indicated that the alteration of OsGLIP gene expression was associated with substantial changes of the levels of lipid species including monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). We show that MGDG and DGDG feeding could attenuate disease resistance. Taken together, our study indicates that OsGLIP1 and OsGLIP2 negatively regulate rice defense by modulating lipid metabolism, thus providing new insights into the function of lipids in plant immunity.

MeSH terms

  • Amino Acid Sequence
  • Carboxylic Ester Hydrolases / genetics
  • Carboxylic Ester Hydrolases / metabolism*
  • Conserved Sequence
  • Disease Resistance* / immunology
  • Down-Regulation
  • Extracellular Space / chemistry
  • Extracellular Space / metabolism
  • Gene Expression Regulation, Plant
  • Homeostasis
  • Lipase / chemistry
  • Lipase / classification
  • Lipase / genetics
  • Lipase / metabolism
  • Lipid Metabolism / immunology
  • Lipid Metabolism / physiology*
  • Lipids / isolation & purification
  • Microscopy, Confocal
  • Oryza / enzymology*
  • Oryza / genetics
  • Oryza / immunology
  • Oryza / ultrastructure
  • Phylogeny
  • Plant Immunity / physiology*
  • Plant Leaves / chemistry
  • Plant Leaves / enzymology
  • Plant Stems / chemistry
  • Plant Stems / enzymology
  • Sequence Alignment
  • Substrate Specificity

Substances

  • Lipids
  • Carboxylic Ester Hydrolases
  • Lipase

Grants and funding

This work was supported by grants from National Natural Science Foundation of China (http://www.nsfc.gov.cn/) (31330061), the National GMO project (http://www.nmp.gov.cn/zxjs/200901/t20090113_2113.htm (2013ZX08009-003-001), and the Shanghai Committee of Science and Technology (http://www.stcsm.gov.cn/) (14JC1406700). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.