Connecting the plant vasculature to friend or foe

Summary The plant vasculature transports water, sugars, hormones, RNA s and proteins. Such critical functions need to be protected from attack by pests and pathogens or from damage by wounding. Plants have developed mechanisms to repair vasculature when such protections fail and to even initiate new vascular connections to tissues supporting symbionts. The developmental phenomena underlying vascular repair and rewiring are therefore critical for horticultural grafting, for plant infection and for mutualist associations with rhizosphere microbes. Despite the biological and economic interest, we are only beginning to understand how plants connect and reconnect their vasculature to a wide variety of organisms. Here, I discuss recent work and future prospects for this emerging field. Contents Summary 1611 I. Introduction 1611 II. Connecting veins within a plant: leaf formation 1612 III. Connecting veins within a plant: wound healing 1612 IV. Connecting veins between plants: plant grafting 1614 V. Connecting veins between plants: parasitic plant infections 1614 VI. Connecting veins to symbionts: nematode infections 1614 VII. Connecting veins to symbionts: bacterial infections 1615 VIII.