Xanthomonas fragariae (Xaf) is the cause of strawberry crown dry cavity rot and strawberry leaf angular spots. Despite having a long evolutionary history with strawberries, the plant-pathogen interaction is poorly understood. Pathogenicity for most plant pathogens is mostly dependent on the type-III secretion system, which introduces virulence type III effectors (T3Es) into eukaryotic host cells. Understanding how effector proteins escape from plant surveillance is important for plant breeding and resistance deployment. In this study, a core conserved secreted effector called Xanthomonas Outer Protein K (XopK) was identified in Xaf strain YL19. Transgenic strawberries expressing XopK exhibit increased susceptibility to Xaf YL19, and this was associated with weakened stomatal immunity. Additionally, abscisic acid (ABA) accumulation and signaling were significantly suppressed in XopK-OX strawberry plants. Overexpression of XopK also inhibited ABA- and methyl jasmonate (MeJA)-induced stomatal closure in strawberry leaves. Moreover, endogenous ABA is critical for Xaf-induced stomatal closure. These results suggested that Xaf YL19 uses XopK to suppress ABA signaling to disrupt stomatal closure allowing bacterial colonization for disease development.
Keywords: Abscisic acid; Methyl jasmonate; Stomatal immunity; Strawberry; Xanthomonas fragariae.
Copyright © 2024 Elsevier Masson SAS. All rights reserved.