AUTHOR=Ziye Shang , Yuqiang Zhao , Shitong Wu , Ling Cai , Chenchao Sun , Jun Wang , Weirong Gong , Yanli Tian , Baishi Hu 

TITLE=ClpA affects the virulence of Paracidovorax citrulli on melon by regulating RepA

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1431029

DOI=10.3389/fmicb.2024.1431029

ISSN=1664-302X

ABSTRACT=<p>ClpA is a widely conserved protease in bacteria that plays a key role in virulence. To investigate its specific mechanism of action in the pathogenicity of <italic>Paracidovorax citrulli</italic> (formerly <italic>Acidovorax citrulli)</italic>, we constructed a <italic>ClpA</italic> deletion mutant, Δ<italic>ClpA</italic>. The Δ<italic>ClpA</italic> mutant of <italic>P. citrulli</italic> displayed reduced virulence on melon seedlings, and reduced motility, swarming ability, and antioxidant capacity. On the other hand, the <italic>ClpA</italic> deletion of <italic>P. citrulli</italic> mutant reduced the resistance to elevated temperature and enhanced biofilm formation ability. Using qRT-PCR, we observed that <italic>ClpA</italic> negatively regulates the expression of the virulence-related genes <italic>virB</italic>, <italic>pilR</italic>, <italic>pilA</italic>, and <italic>fliM</italic>, while positively regulating <italic>hrpG</italic>, <italic>hrcQ</italic>, and <italic>trbC</italic>. Bacterial double hybrid and Glutathione-S-transferase pulldown (GST-pulldown) results showed that ClpA interacts directly with RepA, and negatively regulates the expression of <italic>RepA</italic>. After deletion of the <italic>RepA</italic> gene, the pathogenicity of <italic>P. citrulli</italic> was lost, biofilm formation ability was enhanced, and the expression of <italic>hrpG</italic>, <italic>pilR</italic>, and <italic>trbC</italic> was positively regulated. These results indicate that ClpA plays a key role in the regulation of several virulence traits of <italic>P. citrulli</italic>, paving the way for future studies to better elucidate the virulence mechanisms of this bacterial plant pathogen.</p>