SNARE-encoding genes VdSec22 and VdSso1 mediate protein secretion required for full virulence in Verticillium dahliae

Authors: WANG, JIE - Chinese Academy Of Agricultural Sciences; TIAN, LI - Qufu Normal University; ZHANG, DAN-DAN - Chinese Academy Of Agricultural Sciences; SHORT, DYLAN - University Of California; ZHOU, LEI - Chinese Academy Of Agricultural Sciences; SONG, SHUANG-SHUANG - Qufu Normal University; LIU, YAN - Qufu Normal University; WANG, DAN - Chinese Academy Of Agricultural Sciences; KONG, ZHI-QIANG - Chinese Academy Of Agricultural Sciences; CUI, WEI-YI - Chinese Academy Of Agricultural Sciences; MA, XUE-F - Chinese Academy Of Agricultural Sciences; Klosterman, Steven; SUBBARAO, KRISHNA - University Of California; CHEN, JIE-YIN - Chinese Academy Of Agricultural Sciences; DAI, XIAO-FENG - Chinese Academy Of Agricultural Sciences

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2018
Publication Date: 2/8/2018
Citation: Wang, J., Tian, L., Zhang, D., Short, D.P., Zhou, L., Song, S., Liu, Y., Wang, D., Kong, Z., Cui, W., Ma, X., Klosterman, S.J., Subbarao, K.V., Chen, J., Dai, X. 2018. SNARE-encoding genes VdSec22 and VdSso1 mediate protein secretion required for full virulence in Verticillium dahliae. Molecular Plant-Microbe Interactions. 32(6):651-664. http://doi.org/10.1094/MPMI-12-17-0289-R.
DOI: https://doi.org/10.1094/MPMI-12-17-0289-R

Interpretive Summary: The fungus Verticillium dahliae is the cause of devastating vascular wilt diseases on over 200 plant species worldwide. Determining how this pathogen causes disease, and specifically the mechanisms at the cellular and molecular level by which the pathogen delivers proteins extracellularly that interact with the host plants is valuable to help to control this pathogen. The pathogen secretes proteins to degrade the host cell walls, and cause toxicity to the plant cells. The ability to prevent, inhibit or otherwise control the secretion of these proteins may enable the development new types of fungicides that target these processes or alternative control approaches. In this study, two genes were identified in V. dahliae that are responsible for the secretion of some of the proteins that cause disease symptoms on the plant. Based on known functions of their counterpart proteins in yeast, these proteins allow vesicle fusion inside of cells and with the plasma membrane to release transported proteins. We showed that these two proteins control the extracelluar release of some of the proteins involved in cell wall degradation, and that the release of other proteins apparently relies on pathways independent of these two proteins.

Technical Abstract: Proteins that mediate cellular and subcellular membrane fusion are key factors in vesicular trafficking in all eukaryotic cells, including the secretion and transport of plant pathogen virulence factors. In this study, we identified vesicle fusion components that included 22 soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), 4 Sec1/Munc18 (SM) family proteins, and 10 Rab GTPases encoded in the genome of the vascular wilt pathogen Verticillium dahliae, strain Vd991. Targeted deletion of two SNARE-encoding genes in V. dahliae, VdSec22 and VdSso1, significantly reduced virulence of both of these mutants on cotton, as compared with the wild type Vd991 strain. Comparative analyses of the secreted protein content (exoproteome) revealed that an abundance of enzymes involved in carbohydrate hydrolysis are regulated by VdSec22 or VdSso1. Consistent with a role of these enzymes in plant cell wall degradation, pectin, cellulose, and xylan utilization were each reduced in the VdSec22 or VdSso1 mutant strains, and there was also a loss of exoproteome cytotoxic activity on cotton leaves in both mutant strains. Comparisons with a pathogenicity-related exoproteome revealed that several known virulence factors were not regulated by the VdSec22 or VdSso1, and that some of the proteins regulated by VdSec22 or VdSso1 also displayed different secretory characteristics, some of which lack a typical signal peptide, suggesting that V. dahliae could employ several secretory routes to transport proteins to extracellular sites during infection.