Abstract
Xylella fastidiosa strain 9a5c is a gram-negative phytopathogen that is the causal agent of citrus variegated chlorosis (CVC), a disease that is responsible for economic losses in Brazilian agriculture. The most well-known mechanism of pathogenicity for this bacterial pathogen is xylem vessel occlusion, which results from bacterial movement and the formation of biofilms. The molecular mechanisms underlying the virulence caused by biofilm formation are unknown. Here, we provide evidence showing that virulence-associated protein D in X. fastidiosa (Xf-VapD) is a thermostable protein with ribonuclease activity. Moreover, protein expression analyses in two X. fastidiosa strains, including virulent (Xf9a5c) and nonpathogenic (XfJ1a12) strains, showed that Xf-VapD was expressed during all phases of development in both strains and that increased expression was observed in Xf9a5c during biofilm growth. This study is an important step toward characterizing and improving our understanding of the biological significance of Xf-VapD and its potential functions in the CVC pathosystem.
Highlights
Xylella fastidiosa is a gram-negative, xylem-inhabiting bacterium that is a causal agent in important global diseases in agricultural crops, such as plum, almond, peach, coffee, and grapevine [1]
Protein expression analyses in two X. fastidiosa strains, including virulent (Xf9a5c) and nonpathogenic (XfJ1a12) strains, showed that Xf-VapD was expressed during all phases of development in both strains and that increased expression was observed in Xf9a5c during biofilm growth
The VapD sequences analyzed in groups 1, 2 and 3 were found to be related to the Cas2 family of CRISPR/Cas system-associated proteins
Summary
Xylella fastidiosa is a gram-negative, xylem-inhabiting bacterium that is a causal agent in important global diseases in agricultural crops, such as plum, almond, peach, coffee, and grapevine [1]. X. fastidiosa is transmitted by sharpshooter leafhoppers, and once the pathogen enters the xylem, it spreads through channels called bordered pits that connect vessels [4]. The main pathogenic mechanism of X. fastidiosa occurs when the organism blocks water transport through vessels by forming systemic biofilms. A biofilm is a matrix that is composed of factors including extracellular polymeric substance (EPS), proteins, and nucleic acids [5]. This architecture increases the resistance of the biofilm
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