Migration of Type III Secretion System Transcriptional Regulators Links Gene Expression to Secretion

mBio

Dimitrios Anagnostou¹  Nickolas J. Panopoulos¹  Anastasia D. Gazi²  Michael Kokkinidis²  Spyridoula N. Charova²  Konstantina Psatha²  Michalis Aivaliotis²  Efstratios Mylonas²  Charalambos Pozidis²  Blanca Sabarit³  Carmen R. Beuzon³ 

[1] Department of Biology, University of Crete, Heraklion, Crete, Greece;Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology–Hellas (IMBB-FORTH), Heraklion, Crete, Greece;Instituto de Hortofruticultura Subtropical y Mediterranea La Mayora, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Departamento de Biología Celular, Genética y Fisiología, Málaga, Spain;

关键词: Erwinia amylovora;    Pseudomonas syringae pv. phaseolicola;    type III secretion system (T3SS);    gatekeeper complex;   

DOI  :  10.1128/mBio.01096-18

来源: DOAJ

【 摘 要 】

ABSTRACT Many plant-pathogenic bacteria of considerable economic importance rely on type III secretion systems (T3SSs) of the Hrc-Hrp 1 family to subvert their plant hosts. T3SS gene expression is regulated through the HrpG and HrpV proteins, while secretion is controlled by the gatekeeper HrpJ. A link between the two mechanisms was so far unknown. Here, we show that a mechanistic coupling exists between the expression and secretion cascades through the direct binding of the HrpG/HrpV heterodimer, acting as a T3SS chaperone, to HrpJ. The ternary complex is docked to the cytoplasmic side of the inner bacterial membrane and orchestrates intermediate substrate secretion, without affecting early substrate secretion. The anchoring of the ternary complex to the membranes potentially keeps HrpG/HrpV away from DNA. In their multiple roles as transcriptional regulators and gatekeeper chaperones, HrpV/HrpG provide along with HrpJ potentially attractive targets for antibacterial strategies. IMPORTANCE On the basis of scientific/economic importance, Pseudomonas syringae and Erwinia amylovora are considered among the top 10 plant-pathogenic bacteria in molecular plant pathology. Both employ type III secretion systems (T3SSs) of the Hrc-Hrp 1 family to subvert their plant hosts. For Hrc-Hrp 1, no functional link was known between the key processes of T3SS gene expression and secretion. Here, we show that a mechanistic coupling exists between expression and secretion cascades, through formation of a ternary complex involving the T3SS proteins HrpG, HrpV, and HrpJ. Our results highlight the functional and structural properties of a hitherto-unknown complex which orchestrates intermediate T3SS substrate secretion and may lead to better pathogen control through novel targets for antibacterial strategies.

【 授权许可】

Unknown