CsrD regulates amylovoran biosynthesis and virulence in Erwinia amylovora in a novel cyclic-di-GMP dependent manner.

Roshni R Kharadi, George W Sundin

Molecular plant pathology 2022 Aug

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Erwinia amylovora is an economically devastating plant pathogen that causes fire blight disease in members of the Rosaceae family, most notably in apple and pear. The exopolysaccharide amylovoran is a pathogenicity determinant in E. amylovora and a major component of the extracellular matrix of biofilms formed within the xylem vasculature of the host plant. The second messenger cyclic-di-GMP (c-di-GMP) has been reported to positively regulate the transcription of amsG (the first gene in the 12-gene amylovoran [ams] biosynthetic operon), thus impacting amylovoran production. However, the regulatory mechanism by which this interaction occurs is largely unknown. Here, we report that c-di-GMP can bind to specific residues in the EAL domain of the E. amylovora protein CsrD. CsrD and RNase E regulate the degradation of the sRNA CsrB in E. amylovora. When CsrD is bound to c-di-GMP, there is an enhancement in the level of RNase E-mediated degradation of CsrB, which then alters amsG transcription. Additionally, csrD was also found to positively contribute to virulence and biofilm formation. We thus present a pathway of conditional regulation of amylovoran production mediated by changing intracellular levels of c-di-GMP, which impacts disease progression. © 2022 The Authors. Molecular Plant Pathology published by British Society for Plant Pathology and John Wiley & Sons Ltd.

Citation

Roshni R Kharadi, George W Sundin. CsrD regulates amylovoran biosynthesis and virulence in Erwinia amylovora in a novel cyclic-di-GMP dependent manner. Molecular plant pathology. 2022 Aug;23(8):1154-1169