In:
Journal of Bacteriology, American Society for Microbiology, Vol. 188, No. 10 ( 2006-05-15), p. 3682-3696
Abstract:
Phytoplasmas
(“ Candidatus Phytoplasma,” class Mollicutes ) cause disease in hundreds of economically
important plants and are obligately transmitted by sap-feeding insects of the order Hemiptera, mainly leafhoppers and psyllids. The 706,569-bp
chromosome and four plasmids of aster yellows phytoplasma strain witches' broom (AY-WB) were sequenced and compared to the onion yellows
phytoplasma strain M (OY-M) genome. The phytoplasmas have small repeat-rich genomes. This comparative analysis revealed that the
repeated DNAs are organized into large clusters of potential mobile units (PMUs), which contain tra5 insertion
sequences (ISs) and genes for specialized sigma factors and membrane proteins. So far, these PMUs appear to be unique to phytoplasmas.
Compared to mycoplasmas, phytoplasmas lack several recombination and DNA modification functions, and therefore, phytoplasmas may use
different mechanisms of recombination, likely involving PMUs, for the creation of variability, allowing phytoplasmas to adjust to the diverse
environments of plants and insects. The irregular GC skews and the presence of ISs and large repeated sequences in the AY-WB and OY-M
genomes are indicative of high genomic plasticity. Nevertheless, segments of ∼250 kb located between the lplA and glnQ genes are syntenic between the two phytoplasmas and
contain the majority of the metabolic genes and no ISs. AY-WB appears to be further along in the reductive evolution process than OY-M. The
AY-WB genome is ∼154 kb smaller than the OY-M genome, primarily as a result of fewer multicopy sequences, including PMUs. Furthermore,
AY-WB lacks genes that are truncated and are part of incomplete pathways in OY-M.
Type of Medium:
Online Resource
ISSN:
0021-9193
,
1098-5530
DOI:
10.1128/JB.188.10.3682-3696.2006
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2006
detail.hit.zdb_id:
1481988-0
SSG:
12
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