MoVam7, a Conserved SNARE Involved in Vacuole Assembly, Is Required for Growth, Endocytosis, ROS Accumulation, and Pathogenesis of Magnaporthe oryzae

Abstract

Soluble NSF attachment protein receptor (SNARE) proteins play a central role in membrane fusion and vesicle transport of eukaryotic organisms including fungi. We previously identified MoSce22 as a homolog of Saccharomyces cerevisiae SNARE protein Sec22 to be involved in growth, stress resistance, and pathogenicity of Magnaporthe oryzae. Here, we provide evidences that MoVam7, an ortholog of S. cerevisiae SNARE protein Vam7, exerts conserved functions in vacuolar morphogenesis and functions in pathogenicity of M. oryzae. Staining with neutral red and FM4-64 revealed the presence of abnormal fragmented vacuoles and an absence of the Spitzenkörper body in the ΔMovam7 mutant. The ΔMovam7 mutant also exhibited reduced vegetative growth, poor conidiation, and failure to produce the infection structure appressorium. Additionally, treatments with cell wall perturbing agents indicated weakened cell walls and altered distributions of the cell wall component chitin. Furthermore, the ΔMovam7 mutant showed a reduced accumulation of reactive oxygen species (ROS) in the hyphal apex and failed to cause diseases on the rice plant. In summary, our studies indicate that MoVam7, like MoSec22, is a component of the SNARE complex whose functions in vacuole assembly also underlies the growth, conidiation, appressorium formation, and pathogenicity of M. oryzae. Further studies of MoVam7, MoSec22, and additional members of the SNARE complex are likely to reveal critical mechanisms in vacuole formation and membrane trafficking that is linked to fungal pathogenicity.

Mitochondrial fission protein MoFis1 mediates conidiation and is required for full virulence of the rice blast fungus Magnaporthe oryzae

“…Cell wall composition in M. oryzae plays an important role in full virulence; defects of cell walls can affect appressorium formation and result in defective pathogenicity (Dou et al 2011;Xu 2000;Xu et al 1998). Cell wall integrity tests were conducted by growing a 5 mm mycelium plug of Guy11 and mutant fungi on CM medium plates containing 200 g/mL of Congo red (Sangon Co., Shanghai, China) followed by incubation at 25 • C under continuous light.…”

Autophagy vitalizes the pathogenicity of pathogenic fungi

“…81 MoSec22 and MoVam7, the orthologs of yeast SNARE proteins Sec22 and Vam7, can also be demonstrated to have functions in vacuole assembly, which underlie the growth, conidiation, appressorium formation, and pathogenicity of M. oryzae. 82,83 Similarly, MoMon1 and MoYpt7 are the orthologs of the yeast proteins Mon1 and Ypt7.…”

MoVrp1, a putative verprolin protein, is required for asexual development and infection in the rice blast fungus Magnaporthe oryzae

“…Extracellular peroxidase and laccase are required for the pathogenicity of certain fungi7344041. CR and 2’-azino-di-3- ethylbenzathiazoline-6-sulfonate (ABTs) are used as indicators for the presence of extracellular laccase and peroxidase, respectively42.…”

“…Recently studies showed that endocytosis is conserved from yeast to filamentous fungi, and mammalian cells, which emphasizes the importance of endocytosis for eukaryotic cells5. In yeast and plant pathogenic fungi, endocytosis is extensively involved in cell polarity establishment, hyphal growth, and/or virulence67891011.…”

“…Endocytosis plays a crucial role in conidial cells to detect certain external signals, and is required for hyphal tip growth28. Previously, we characterized two members of the secretory soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), MoSec22 and MoVam7 in M. oryzae , which are required for membrane trafficking, cellular growth, stress tolerance and pathogenicity710. Our previous studies also showed that MoArk1, as a homolog of Ark1 in S. cerevisiae , which showed an actin-like localization pattern by localizing to the hyphal apices strongly affects organization of the cortical actin cytoskeleton.…”