Abstract

Plants, unlike animals, lack specialized mobile immune cells, so they do not have an adaptive immune system. Instead, plants can launch specific, self-tolerant immune responses and establish immune memory. Plants possess defense mechanisms that efficiently detect and ward off potentially dangerous microorganisms. These defense mechanisms start with multiple signalling processes responsible for sensation, recognition, signal collection and conveying information between cells. Recognition occurs when microbial or pathogen-associated molecular patterns (MAMPs or PAMPs) are detected, leading to MAMP- or PAMP-triggered immunity (MTI or PTI). Plant cells also recognize pathogens through effector-triggered immunity (ETI), which relies on the function of the pathogen’s avirulence (Avr) gene-coded effector proteins and host’s resistance (R) gene-coded R proteins, resulting in the activation of apoptosis-like cell death, known as the hypersensitive response. In addition, reactive oxygen species (ROS) act as a double-edged sword; they are either toxic or versatile signalling molecules in plants. ROS generation is an integral part of hormone regulation and function in plant defense mechanisms. Plant hormones are also implicated in plant defense signalling pathways; salicylic acid, jasmonic acid, and ethylene have been increasingly studied in plant responses to pathogens. These innate immune system components interact with each other and provide protection against invading pathogens. We review advances in understanding the molecular aspects of plant defense mechanisms and describe the role of ROS, mitogen-activated protein kinase (MAPK) cascades, and hormones in modulating defense responses. We also provide an overview of how these plant defense components interact for a balanced and appropriate defense response.

摘要

与动物不同，植物缺乏专门的移动免疫细胞，因此它们没有适应性免疫系统。相反，植物可以启动特定的、自我耐受的免疫反应并建立免疫记忆。植物拥有有效检测和抵御潜在危险微生物的防御机制。这些防御机制始于负责感觉、识别、信号收集和在细胞之间传递信息的多个信号过程。当检测到微生物或病原体相关分子模式（MAMP 或 PAMP）时，就会发生识别，从而导致 MAMP 或 PAMP 触发的免疫（MTI 或 PTI）。植物细胞还通过效应触发免疫 (ETI) 识别病原体，它依赖于病原体无毒力的功能 ( Avr) 基因编码的效应蛋白和宿主的抗性 ( R) 基因编码的 R 蛋白，导致细胞凋亡样细胞死亡的激活，称为过敏反应。此外，活性氧（ROS）是一把双刃剑。它们在植物中要么是有毒的，要么是通用的信号分子。ROS的产生是植物防御机制中激素调节和功能的一个组成部分。植物激素也与植物防御信号通路有关。水杨酸、茉莉酸和乙烯在植物对病原体的反应中的研究越来越多。这些先天免疫系统成分相互作用，并提供对入侵病原体的保护。我们回顾了在理解植物防御机制的分子方面的进展，并描述了 ROS、丝裂原活化蛋白激酶 (MAPK) 级联的作用，和调节防御反应的激素。我们还概述了这些植物防御组件如何相互作用以实现平衡和适当的防御响应。