Damage activates EVG1 to suppress vascular differentiation during regeneration in Arabidopsis thaliana
Plants possess remarkable regenerative abilities to form de novo vasculature after damage and in response to pathogens that invade and withdraw nutrients. To look for common factors that affect vascular formation upon stress, we searched for Arabidopsis thaliana genes differentially expressed during Agrobacterium infection, nematode infection and plant grafting. One such gene was cell-wall associated and highly induced by all three stresses. Mutations in it enhanced ectopic xylem formation in Vascular cell Induction culture System Using Arabidopsis Leaves (VISUAL) and enhanced graft formation and was thus named ENHANCER OF VISUAL AND GRAFTING 1 (EVG1). Mutated evg1 inhibited cambium development and callus formation yet promoted tissue attachment, syncytium size, phloem reconnection and xylem formation. evg1 affected abscisic acid and cell wall responses and was itself down regulated by ABA. We found mutations in a receptor-like gene, RLP44, had the same regeneration phenotype as EVG1 mutations including enhancing VISUAL and grafting. evg1 and rlp44 mutants affected the expression of many genes in common including those important for successful regeneration and vascular formation. We propose that EVG1 integrates information from cutting, wounding or parasitism stresses and functions with RLP44 to suppress vascular differentiation during regeneration.