The type III secretion system is necessary for the development of a pathogenic and endophytic interaction between Herbaspirillum rubrisubalbicans and Poaceae

Abstract

BackgroundHerbaspirillum rubrisubalbicans was first identified as a bacterial plant pathogen, causing the mottled stripe disease in sugarcane. H. rubrisubalbicans can also associate with various plants of economic interest in a non pathogenic manner.ResultsA 21 kb DNA region of the H. rubrisubalbicans genome contains a cluster of 26 hrp/hrc genes encoding for the type three secretion system (T3SS) proteins. To investigate the contribution of T3SS to the plant-bacterial interaction process we generated mutant strains of H. rubrisubalbicans M1 carrying a Tn5 insertion in both the hrcN and hrpE genes. H. rubrisulbalbicans hrpE and hrcN mutant strains of the T3SS system failed to cause the mottled stripe disease in the sugarcane susceptible variety B-4362. These mutant strains also did not produce lesions on Vigna unguiculata leaves. Oryza sativa and Zea mays colonization experiments showed that mutations in hrpE and hrcN genes reduced the capacity of H. rubrisulbalbicans to colonize these plants, suggesting that hrpE and hrcN genes are involved in the endophytic colonization.ConclusionsOur results indicate that the T3SS of H. rubrisubalbicans is necessary for the development of the mottled stripe disease and endophytic colonization of rice.

A compendium of DNA-binding specificities of transcription factors in Pseudomonas syringae

“…Since the pathogenicity of P. syringae largely depends on T3SS 32 , we were particularly interested in recognizing the TFs that were primarily involved in regulating the T3SS genes. The T3SS component genes are clustered in a 25-kb pathogenicity-related island, whereas the majority of the effector genes are dispersed in the genome 33 . By specifically connecting TFs and target genes that were involved in T3SS, the resulting network included 45 TFs and 46 T3SS genes (Fig.…”

Rhizosphere Microbiome Modulators: Contributions of Nitrogen Fixing Bacteria towards Sustainable Agriculture

“…H. seropedicae perhaps acquired its N fixing capability via “horizontal gene transfer” like other non-rhizobial strains. Like other disease-causing microorganisms of the genus Herbaspirillum , it is fascinating to know that H. seropedicae which is non-pathogenic has the entire genetic make-up for type I, II, III, V, VI and IV pili which it uses to facilitate communication with its host plant [ 106 ]. The type III is now known to be involved in the “initial signal communication” of Bradyrhizobium elkani and Rhizobium sp.…”

Defining the Genetic Basis of Plant–Endophytic Bacteria Interactions

“…The translocated effector proteins can manipulate the host metabolism and the immune system response. H. rubrisubalbicans M1 T3SS mutants were less successful in endophytic colonisation [57]. The efficacy of the secreted effector proteins by T3SS is maintained by small cytosolic chaperones [87].…”