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.

脂质和脂质代谢产物在植物与微生物的相互作用中起着重要的作用。尽管脂肪酶在脂质体内平衡和种子油的生物合成中进行了广泛的研究，但是脂肪酶在植物免疫中的作用仍是未知的。特别地，以保守的GDSL基序为特征的GDSL酯酶/脂肪酶是具有广泛底物特异性的脂解酶的亚家族。在这里，我们从功能上鉴定了水稻免疫应答中的两种GDSL脂肪酶OsGLIP1和OsGLIP2。OsGLIP1和OsGLIP2的表达被病原体感染和水杨酸（SA）处理抑制。OsGLIP1主要在叶和叶鞘中表达，而OsGLIP2在延长节间表现出高表达。生化分析表明，OsGLIP1和OsGLIP2是可以水解脂质底物的功能性脂肪酶。同时下调OsGLIP1和OsGLIP2可以增加植物对细菌和真菌病原体的抗性，而OsGLIP1和OsGLIP2的抗病性植物的过表达严重受损，表明这两个基因均是抗病性的负调控因子。OsGLIP1和OsGLIP2蛋白主要定位在脂质滴和内质网（ER）膜上。OsGLIP蛋白正确的细胞定位对于它们的免疫功能是必不可少的。全面的脂质谱分析表明，OsGLIP的改变基因表达与包括单半乳糖基二酰基甘油（MGDG）和二半乳糖基二酰基甘油（DGDG）的脂质种类水平的重大变化有关。我们表明，MGDG和DGDG喂养可以减弱抗病能力。两者合计，我们的研究表明OsGLIP1和OsGLIP2通过调节脂质代谢负调控水稻防御能力，从而为脂质在植物免疫中的功能提供了新的见识。