图1. FER介导的抗病相关途径示意图
FER定位于质膜微区, 能够识别尖孢镰刀菌(Fusarium oxysporium)分泌的F-RALF, 阻断AHA2介导的H⁺外流, 从而诱导根系胞外环境碱化, 增强真菌对植物的致病力。在此过程中, 尖孢镰刀菌细胞中丝裂原活化蛋白激酶(MAPK)途径中的Fmk1对其侵染至关重要。FER与RALF23相互作用, 负向调控茉莉酸和冠菌素信号, 正向促进植物免疫; 拟南芥(Arabidopsis thaliana) SITE-1蛋白酶(S1P)剪切内源快速碱化因子(RALF)前体肽, 而RALF与拟南芥FER相互作用抑制FLS2、BAK1和EFR免疫复合物的形成, 抑制植物免疫。FER可能调节细胞内活性氧的积累和MAPK活性。F-RALF: 尖孢镰刀菌分泌的快速碱化因子; AHA2: H⁺-ATPase 2; RIPK: RESISTANCE TO Pseudomonas syringae pv. maculicola 1-INDUCED PROTEIN KINASE; Fmk1: 一种保守的真菌丝裂原活化蛋白激酶(MAPK); flg22: 鞭毛蛋白抗原表位22; RALF23: 内源性肽快速碱化因子23; MYC2: MYELOCYTOMATOSIS PRO- TEINS 2; EFR: ELONGATION FACTOR THERMO UNSTABLE RECEPTOR; FLS2: FLAGELLIN-SENSING 2; BAK1: BRAS- SINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1; RLCK: 类受体胞质激酶; MAPK: 丝裂原活化蛋白激酶; NADPH: 烟酰胺腺嘌呤二核苷酸磷酸

Figure 1. A schematic diagram of the disease resistance pathway mediated by FER The microdomain-localized
FER in the plasma membrane can recognize F-RALF secreted by Fusarium oxysporium and further block AHA2-mediated H⁺ outflow, thus inducing the alkalinization of extracellular environment and increasing the pathogenicity of F. oxysporium. During this process, Fmk1 in the mitogen-activated protein kinase (MAPK) pathway in F. oxysporium cells is critical for infection. FER interacts with RALF23, negatively regulating JA and COR signals and positively promoting plant immunity; the SITE-1 protease (S1P) can digest endogenous fast alkalization factor (RALF) precursor peptide and the mature RALF further interacts with FER to inhibit the formation of immune complexes (mainly FLS2, BAK1, and EFR), inhibits plant immunity. FER may regulate intracellular ROS accumulation and MAPK signaling. F-RALF: F. oxysporium RALF; AHA2: H⁺-ATPase 2; RIPK: RESISTANCE TO Pseudomonas syringae pv. maculicola 1-INDUCED PROTEIN KINASE; Fmk1: A con- served fungal MAPK; flg22: Flagellin epitope 22; RALF23: The endogenous peptide RALF 23; MYC2: MYELOCYTOMATOSIS PROTEINS 2; EFR: ELONGATION FACTOR THERMO UNSTABLE RECEPTOR; FLS2: FLAGELLIN-SENSING 2; BAK1: BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1; RLCK: Receptor-like cytoplasmic kinase; MAPK: Mitogenactivated protein kinase; NADPH: Nicotinamide adenine dinucleotide phosphate