进化的植物-病原体军备竞赛为植物配备了可以防御病原体的免疫系统。模式触发免疫和效应子触发免疫是先天免疫的两个主要分支,它们共享免疫反应。包括氧化爆发,转录重编程,和细胞壁修饰,如木质素沉积。在之前的研究中,我们报道,木质素在病原体感染的拟南芥叶片中迅速积累,并充当机械屏障,在空间上限制病原体和细胞死亡。木质素沉积到细胞壁是一个三步过程:单寡核苷酸生物合成,运输,和聚合。虽然单寡核苷酸生物合成和聚合是相对较好的理解,单体转运机制尚不清楚。在这项研究中,我们表明巨自噬/自噬调节病原体诱导的木质素形成。在自噬缺陷型atg(自噬相关)突变体中,木质素和其他免疫反应受损。在显微镜分析中,单木素响应病原体感染而形成点状结构,并与自噬囊泡共定位。此外,自噬活性和木质素积累在dnd1中均增强(防御,无死亡1)抗病性提高但无细胞死亡的突变体,并且将dnd1-1与atg突变体杂交导致木质素缺乏,进一步支持木质素的形成需要自噬。总的来说,这些发现表明木质化,尤其是垄断运输,是通过自噬膜运输实现植物免疫。缩写:ABC转运体:ATP结合盒转运体;ACD2/AT4G37000:加速细胞死亡2;ATG:自噬相关;C3\'H/AT2G40890:对香豆酰基shikimate3-羟化酶;C4H/AT2GG30A:肉桂酸4-羟化酶1;C4H/AT2G2C3Ccafferosp1:C无死亡1;CNGC2:环核苷酸门控通道2;ER:内质网;ESB1/AT2G28670/DIR10:增强的亚细素1;ETI:效应子触发的免疫;EV:胞外囊泡;F5H/AT4G36220:阿魏酸-5-羟化酶;Fluo-3AM:Fluo-3γ-3γ:Fluo-3γ-3番茄DC3000;PTI:模式触发免疫;SA:水杨酸;SD:标准偏差;SID2/AT1G7410:SA诱导缺陷型2;UGT:UDP-葡萄糖基转移酶;UPLC:超高效液相色谱;UPS:非常规蛋白质分泌;V-ATPase:液泡型H+易位ATPase。
The evolutionary plant-pathogen arms race has equipped plants with the immune system that can defend against pathogens. Pattern-triggered immunity and effector-triggered immunity are two major branches of innate immunity that share immune responses, including oxidative bursts, transcriptional reprogramming, and cell wall modifications such as lignin deposition. In a previous study, we reported that lignin rapidly accumulates in pathogen-infected Arabidopsis leaves and acts as a mechanical barrier, spatially restricting pathogens and cell death. Lignin deposition into the cell wall is a three-step process: monolignol biosynthesis, transport, and polymerization. While monolignol biosynthesis and polymerization are relatively well understood, the mechanism of monolignol transport remains unclear. In this study, we show that macroautophagy/autophagy modulates pathogen-induced lignin formation. Lignification and other immune responses were impaired in autophagy-defective atg (autophagy-related) mutants. In microscopy analyses, monolignols formed punctate structures in response to pathogen infection and colocalized with autophagic vesicles. Furthermore, autophagic activity and lignin accumulation were both enhanced in
dnd1 (defense, no death 1) mutant with elevated disease resistance but no cell death and crossing
dnd1-1 with atg mutants resulted in a lignin deficit, further supporting that lignin formation requires autophagy. Collectively, these findings demonstrate that lignification, particularly monolignol transport, is achieved through autophagic membrane trafficking in plant immunity.Abbreviations: ABC transporter: ATP-binding cassette transporter; ACD2/AT4G37000: accelerated cell death 2; ATG: autophagy-related; C3\'H/AT2G40890: p-coumaroyl shikimate 3-hydroxylase; C4H/AT2G30490: cinnamate 4-hydroxylase; CA: coniferyl alcohol; CaMV: cauliflower mosaic virus; CASP: Casparian strip membrane domain protein; CASPL: CASP-like protein; CBB: Coomassie Brilliant Blue; CCoAOMT1/AT4G34050: caffeoyl-CoA O-methyltransferase 1; CCR1/AT1G15950: cinnamoyl-CoA reductase 1; CFU: colony-forming unit; COMT1/AT5G54160: caffeic acid O-methyltransferase 1; Con A: concanamycin A; DMAC: dimethylaminocoumarin;
DND1/AT5G15410: defense, no death 1; CNGC2: cyclic nucleotide-gated channel 2; ER: endoplasmic reticulum; ESB1/AT2G28670/DIR10: enhanced suberin 1; ETI: effector-triggered immunity; EV: extracellular vesicle; F5H/AT4G36220: ferulate-5-hydroxylase; Fluo-3 AM: Fluo-3 acetoxymethyl ester; GFP: green fluorescent protein; HCT/AT5G48930: p-hydroxycinnamoyl-CoA:quinate/shikimate p-hydroxycinnamoyltransferase; HR: hypersensitive response; LAC: laccase; LTG: LysoTracker Green; LSD1/AT4G200380: lesion stimulating disease 1; PAL1/AT2G37040: phenylalanine ammonia-lyase 1; PAMP: pathogen-associated molecular patterns; PCD: programmed cell death; PE: phosphatidylethanolamine; PRX: peroxidase; Pst DC3000: Pseudomonas syringe pv. tomato DC3000; PTI: pattern-triggered immunity; SA: salicylic acid; SD: standard deviation; SID2/AT1G7410: SA induction-deficient 2; UGT: UDP-glucosyltransferase; UPLC: ultraperformance liquid chromatography; UPS: unconventional protein secretion; V-ATPase: vacuolar-type H+-translocating ATPase.