Disruption of gspD and its Effects on Endoglucanase and Filamentous Phage Secretion in Ralstonia solanacearum

Abstract

Ralstonia solanacearum is a phytopathogenic bacterium that causes bacterial wilt disease in many agricultural, horticultural and ornamental crops. During pathogenesis, R. solanacearum synthesizes and secretes cell wall degrading enzyme (CWDE) such as endoglucanase through type II secretion system. On the other hand, the virulence of R. solanacearum is also affected by filamentous phage infection and is secreted through cell-wall membrane via secretin-like channel. R. solanacearum is known to have a secretin channel to secrete its virulence factors, such as GspD, a type II secretion system secretin. To confirm that GspD have a role on the secretin of endoglucanase and RSS1 phage, we constructed a gspD mutant that lacks secretin formation on the cell membrane of R. solanacearum. The results showed that a gspD mutant only abolished to secrete endoglucanase enzyme, but not RSS1 secretin. According to the RSS1 genomic organization, we found that RSS1 phage has a gene responsible for secretin-like protein due to phage secretion through cell membrane.