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Electron microscopy of the novel barley yellow streak mosaic virus
1Department of Plant Pathology, Montana State University, Bozeman 59717.
Abstract:
Unique particles of barley yellow streak mosaic virus (BYSMV) were detected in diseased barley, wheat, and several species of grass. They appeared to be about 64 nm in width and from 127 nm to an astonishing 4000 nm in length. Individual particles were circular in transverse section. The outermost layer of each particle seemed to be a membrane-like envelope. The internal structure of many particles was bead-like. Some particles had centers that were translucent. The BYSMV particles were distributed throughout the leaf, sheath, root, and awn organs of barley. Virus particles were present in all cell types of the epidermis, mesophyll, phloem, and xylem. However, mesophyll cells contained the greatest number of particles. Most BYSMV particles occurred in large clusters of quasi-parallel arrays. Both individual and groups of particles were located within the cavities of ER elements. Ribosomes were attached to some outer surfaces of the ER bounding membrane. BYSMV particles are unique because they do not resemble any in presently classified groups or families of plant viruses: they are, however, similar to those of some unclassified viruses that infect insects.
Insights
Unique barley yellow streak mosaic virus (BYSMV) particles were found in diseased plants. These distinctive virus particles, unlike any classified plant viruses, were observed in various tissues and cell types.
Area of Science:
- Plant Virology
- Molecular Biology
- Microscopy
Background:
- Barley yellow streak mosaic virus (BYSMV) is a plant pathogen affecting cereal crops.
- Understanding virus morphology and distribution is crucial for disease management.
Purpose of the Study:
- To characterize the unique morphology of BYSMV particles.
- To determine the distribution of BYSMV within infected host plants.
Main Methods:
- Transmission electron microscopy was used to visualize BYSMV particles.
- Infected tissues from barley, wheat, and grasses were examined.
Main Results:
- BYSMV particles exhibit unique morphology: ~64 nm width, 127-4000 nm length, circular cross-section, membrane-like envelope, and bead-like internal structure.
- Particles were distributed in leaf, sheath, root, and awn organs, and across all cell types (epidermis, mesophyll, phloem, xylem), with highest concentration in mesophyll.
- Particles were found in ER cavities, often in quasi-parallel arrays, with attached ribosomes on surrounding membranes.
Conclusions:
- BYSMV particles possess a unique structure not aligning with current plant virus classifications.
- The observed morphology suggests potential relationships with unclassified insect viruses.
- BYSMV has a wide tissue and cellular distribution within its hosts.