Vascular tissue – boon or bane? How pathogens usurp long-distance transport in plants and the defence mechanisms deployed to counteract them

Abstract

Evolutionary emergence of specialised vascular tissues has enabled plants to coordinate their growth and adjust to unfavourable external conditions. Whilst holding a pivotal role in long-distance transport, both xylem and phloem can be encroached on by various biotic factors for systemic invasion and hijacking of nutrients. Therefore, a complete understanding of the strategies deployed by plants against such pathogens to restrict their entry and establishment within plant tissues, is of key importance for the future development of disease-tolerant crops. In this review, we aim to describe how microorganisms exploit the plant vascular system as a route for gaining access and control of different host tissues and metabolic pathways. Highlighting several biological examples, we detail the wide range of host responses triggered to prevent or hinder vascular colonisation and effectively minimise damage upon biotic invasions.