Journal of Plant Pathology & Microbiology

Abstract

Expressional Regulation of the Virulence Gene eglXoA Encoding Endoglucanase, Dependent on HrpXo and Cyclic AMP Receptor-Like Protein (Clp) in Xanthomonas oryzae pv. oryza

Temuujin U and Kang HW

An eglXoA encoding endoglucanase that clustered with eglXoB and eglXoC in Xanthomonas oryzae pv. oryza genome (accession No. AE013598) is a pathogenicity related gene. RT-PCR showed that the in trans eglXoA was transcriptionally regulated by HrpX, a type III secretion regulator, and cyclic AMP receptor-like protein in X. oryzae pv. oryzae (ClpXo), which has been known as a global regulator. Western blot analysis showed that EglXoA is secreted via a type II secretion system and was detected in wild-type strain KACC10859, but not in the mutant strains hrpX::Tn5 and clpXo::Tn5. In an electrophoretic mobility shift assay, the promoter region of eglXoA directly bound to ClpXo. The two consensus eglXoA upstream regions were found to include putative Clp-binding sites with a perfect TCACA-N block in the left arm and a 2/5 matched block, TGT, in the right arm. eglXoA, which encodes endoglucanase, appears to be the first gene of Xoo known to be activated by ClpXo via direct binding to the promoter region. Molecular interaction between HrpX and ClpXo shows that ClpXo acts as transcription regulator of hrpX and binds to promoter region of hrpX.