Type IV Secretion System Is Not Involved in Infection Process in Citrus

Abstract

The type IV secretion system (T4SS) is used by Gram-negative bacteria to translocate protein and DNA substrates across the cell envelope and into target cells. Xanthomonas citri subsp. citri contains two copies of the T4SS, one in the chromosome and the other is plasmid-encoded. To understand the conditions that induce expression of the T4SS in Xcc, we analyzed, in vitro and in planta, the expression of 18 ORFs from the T4SS and 7 hypothetical flanking genes by RT-qPCR. As a positive control, we also evaluated the expression of 29 ORFs from the type III secretion system (T3SS), since these genes are known to be expressed during plant infection condition, but not necessarily in standard culture medium. From the 29 T3SS genes analyzed by qPCR, only hrpA was downregulated at 72 h after inoculation. All genes associated with the T4SS were downregulated on Citrus leaves 72 h after inoculation. Our results showed that unlike the T3SS, the T4SS is not induced during the infection process.

Comparative proteomic analysis of Xanthomonas citri ssp. citri periplasmic proteins reveals changes in cellular envelope metabolism during in vitro pathogenicity induction

“…The remaining primers used in this study have been reported previously in Jacob et al . (). Three endogenous genes whose expression stability was accessed using the Expression Suite Software v1.0.3 (Applied Biosystems) were used ( atpD , rpoB and gyrB ) as controls.…”

“…to non-hosts and in the pathogenicity response to hosts, and are known to be induced in plant-mimicking hrp-inducing medium (Rossier et al, 1999). The hrpD6 and hpa1 genes were highly up-regulated when XAC was grown in Citrus sinensis (Jacob et al, 2014), and hrpG and hrpX were described to be critical for the pathogenicity of X. axonopodis pv. citri (B€ uttner and Bonas, 2010;Guo et al, 2011).…”

“…Primer Express 3.0 software (Applied Biosystems, Foster City, CA, USA) was used to design the primers for the genes mltB (XAC3225) and sodM (XAC2386). The remaining primers used in this study have been reported previously in Jacob et al (2011Jacob et al ( , 2014. Three endogenous genes whose expression stability was accessed using the Expression Suite Software v1.0.3 (Applied Biosystems) were used (atpD, rpoB and gyrB) as controls.…”

Stenotrophomonas maltophilia Encodes a VirB/VirD4 Type IV Secretion System That Modulates Apoptosis in Human Cells and Promotes Competition against Heterologous Bacteria, Including Pseudomonas aeruginosa

“…Looking beyond the genus, we determined that this S. maltophilia T4SS is most related in terms of amino acid similarity to one encoded by the chromosome of Xanthomonas spp. (41,(79)(80)(81) (Fig. S1, blue and purple clades).…”

Genómica comparativa de cepas de Xanthomonas arboricola asociada a Prunus spp.: caracterización de los procesos de infección de la mancha bacteriana de frutales de hueso y almendro

“…campestris, this T4SS has been described as not playing a main role in virulence (Jacob et al, 2014) because the presence of the complete core of components for its expression in X. arboricola varies among strains, regardless of the pathogenic activity. Therefore, VirB/VirD4 secretion system may not be essential for virulence in this species.…”