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Identification and characterization of plasmids from the western aster yellows mycoplasmalike organism
1Department of Plant Pathology, University of California, Davis 95616.
Abstract:
Supercoiled double-stranded DNA molecules (plasmids) were isolated from plants infected with three laboratory strains of western aster yellows mycoplasma-like organism (AY-MLO) by using cesium chloride-ethidium bromide density gradients. Southern blot analysis, using plasmids from the severe strain of AY-MLO (SAY-MLO) as the probe, identified at least four plasmids in celery, aster, and periwinkle plants and in Macrosteles severini leafhopper vectors infected with either the dwarf AY-MLO, Tulelake AY-MLO, or SAY-MLO strain. Plasmids were also detected in two California field isolates of AY-MLO but not in plants infected with the beet leafhopper-transmitted virescence agent, western X, or elm yellows MLOs. SAY-MLO plasmids were 5.2, 4.9, 3.4, and 1.7 kilobase pairs in size. Plasmids isolated from dwarf AY- and Tulelake AY-MLOs were 7.4, 5.1, 3.5, and 1.7 kilobase pairs in size. No evidence was obtained for integration of SAY-MLO plasmids into the MLO chromosome.
Insights
Plasmids were identified in plants and leafhoppers infected with aster yellows mycoplasma-like organisms (AY-MLO). These circular DNA molecules were specific to AY-MLO strains and not found in other related plant pathogens.
Area of Science:
- Plant Pathology
- Molecular Biology
- Microbiology
Background:
- Mycoplasma-like organisms (MLOs) are plant pathogens causing significant agricultural damage.
- Understanding the genetic makeup of MLOs, including plasmids, is crucial for disease management.
- Western aster yellows MLO (AY-MLO) is a significant phytopathogen affecting various crops and ornamental plants.
Purpose of the Study:
- To investigate the presence and characteristics of plasmids in different strains of AY-MLO.
- To determine if plasmids are unique to AY-MLO and absent in other related MLOs.
- To analyze the size and number of plasmids in AY-MLO.
Main Methods:
- Isolation of supercoiled double-stranded DNA molecules (plasmids) from infected plants and insect vectors.
- Cesium chloride-ethidium bromide density gradient centrifugation for plasmid isolation.
- Southern blot analysis using AY-MLO plasmids as probes for detection and characterization.
Main Results:
- At least four plasmids were detected in plants and leafhoppers infected with three laboratory strains of AY-MLO (dwarf, Tulelake, and severe AY-MLO).
- Plasmids were also found in two California field isolates of AY-MLO.
- No plasmids were detected in plants infected with beet leafhopper-transmitted virescence agent, western X, or elm yellows MLOs.
- Specific plasmid sizes were determined for SAY-MLO (5.2, 4.9, 3.4, 1.7 kbp) and dwarf/Tulelake AY-MLOs (7.4, 5.1, 3.5, 1.7 kbp).
Conclusions:
- Plasmids are a common feature of AY-MLO strains.
- The presence of plasmids appears to be specific to AY-MLO, distinguishing them from other MLOs.
- No evidence of plasmid integration into the MLO chromosome was found.