AUTHOR=Zhang Shushe , Wang Xuefeng , He Jun , Zhang Song , Zhao Tingchang , Fu Shimin , Zhou Changyong 

TITLE=A Sec-dependent effector, CLIBASIA_04425, contributes to virulence in ‘Candidatus Liberibater asiaticus’

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1224736

DOI=10.3389/fpls.2023.1224736

ISSN=1664-462X

ABSTRACT=<p>Citrus Huanglongbing (HLB) is the most destructive citrus disease worldwide, mainly caused by ‘<italic>Candidatus</italic> Liberibacter asiaticus’ (<italic>C</italic>Las). It encodes a large number of Sec-dependent effectors that contribute to HLB progression. In this study, an elicitor triggering ROS burst and cell death in <italic>Nicotiana benthamiana</italic>, CLIBASIA_04425 (<italic>C</italic>Las4425), was identified. Of particular interest, its cell death-inducing activity is associated with its subcellular localization and the cytoplasmic receptor <italic>Botrytis</italic>-induced kinase 1 (BIK1). Compared with <italic>C</italic>Las infected psyllids, <italic>C</italic>Las4425 showed higher expression level in planta. The transient expression of <italic>CLas4425</italic> in <italic>N</italic>. <italic>benthamiana</italic> and its overexpression in <italic>Citrus sinensis</italic> enhanced plant susceptibility to <italic>Pseudomonas syringae</italic> pv. <italic>tomato</italic> DC3000 Δ<italic>hopQ1-1</italic> and <italic>C</italic>Las, respectively. Furthermore, the salicylic acid (SA) level along with the expression of genes <italic>NPR1</italic>/<italic>EDS1</italic>/<italic>NDR1</italic>/<italic>PR</italic>s in SA signal transduction was repressed in <italic>C</italic>Las4425 transgenic citrus plants. Taken together, <italic>C</italic>Las4425 is a virulence factor that promotes <italic>C</italic>Las proliferation, likely by interfering with SA-mediated plant immunity. The results obtained facilitate our understanding of <italic>C</italic>Las pathogenesis.</p>