The HrpG/HrpX Regulon of Xanthomonads—An Insight to the Complexity of Regulation of Virulence Traits in Phytopathogenic Bacteria

• Main Authors: Doron Teper, Sheo Shanker Pandey, Nian Wang
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Microorganisms
• Subjects: <i>Xanthomonas</i>; HrpG; HrpX; type 3 secretion system; regulatory networks; phytopathogenic bacteria
• Online Access: https://www.mdpi.com/2076-2607/9/1/187

Bacteria of the genus <i>Xanthomonas</i> cause a wide variety of economically important diseases in most crops. The virulence of the majority of <i>Xanthomonas</i> spp. is dependent on secretion and translocation of effectors by the type 3 secretion system (T3SS) that is controlled by two master transcriptional regulators HrpG and HrpX. Since their discovery in the 1990s, the two regulators were the focal point of many studies aiming to decipher the regulatory network that controls pathogenicity in <i>Xanthomonas</i> bacteria. HrpG controls the expression of HrpX, which subsequently controls the expression of T3SS apparatus genes and effectors. The HrpG/HrpX regulon is activated <i>in planta</i> and subjected to tight metabolic and genetic regulation. In this review, we cover the advances made in understanding the regulatory networks that control and are controlled by the HrpG/HrpX regulon and their conservation between different <i>Xanthomonas</i> spp.