Centre for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Spain.
Genetics Department, Universitat de Barcelona, Barcelona, Spain.
J Exp Bot. 2021 Feb 2;72(2):184-198. doi: 10.1093/jxb/eraa444.
Xylem vascular wilt pathogens cause devastating diseases in plants. Proliferation of these pathogens in the xylem causes massive disruption of water and mineral transport, resulting in severe wilting and death of the infected plants. Upon reaching the xylem vascular tissue, these pathogens multiply profusely, spreading vertically within the xylem sap, and horizontally between vessels and to the surrounding tissues. Plant resistance to these pathogens is very complex. One of the most effective defense responses in resistant plants is the formation of physico-chemical barriers in the xylem tissue. Vertical spread within the vessel lumen is restricted by structural barriers, namely, tyloses and gels. Horizontal spread to the apoplast and surrounding healthy vessels and tissues is prevented by vascular coating of the colonized vessels with lignin and suberin. Both vertical and horizontal barriers compartmentalize the pathogen at the infection site and contribute to their elimination. Induction of these defenses are tightly coordinated, both temporally and spatially, to avoid detrimental consequences such as cavitation and embolism. We discuss current knowledge on mechanisms underlying plant-inducible structural barriers against major xylem-colonizing pathogens. This knowledge may be applied to engineer metabolic pathways of vascular coating compounds in specific cells, to produce plants resistant towards xylem colonizers.
木质部维管束萎蔫病原体在植物中引起毁灭性疾病。这些病原体在木质部的增殖会导致水和矿物质运输的大规模中断，从而导致受感染植物严重萎蔫和死亡。这些病原体到达木质部维管束组织后，会大量繁殖，在木质部汁液中垂直传播，在导管之间以及向周围组织水平传播。植物对这些病原体的抗性非常复杂。抗性植物中最有效的防御反应之一是在木质部组织中形成物理化学屏障。导管腔内的垂直传播受到结构屏障的限制，即木质素和木栓质的侵填体和凝胶。木质部被侵染的导管通过木质素和木栓质的血管涂层，将水平传播到质外体和周围健康的导管和组织，从而被阻止。垂直和水平屏障将病原体在感染部位分隔开来，并有助于将其消除。这些防御反应的诱导在时间和空间上都紧密协调，以避免产生空化和栓塞等有害后果。我们讨论了植物诱导的结构性屏障针对主要木质部定殖病原体的作用机制的现有知识。这些知识可用于工程特定细胞中血管涂层化合物的代谢途径，以生产对木质部定殖体具有抗性的植物。
