Affiliation:
1. State Key Laboratory of Virology, Department of Biochemistry and Molecular Biology, College of Life Sciences, Wuhan University, Hubei 430072, China
Abstract
ABSTRACT
We performed a comprehensive study of the distribution and function of an insertion sequence (IS) element, IS
1237
, in the genome of
Leifsonia xyli
subsp.
cynodontis
, a useful genetic carrier for expressing beneficial foreign genes in plants. Two shorter IS
1237
isoforms, IS
1237
d1 and IS
1237
d2 resulting from precise deletion between two nonperfect repeats, were found in the bacterial genome at a level that was one-fifth the level of wild-type IS
1237
. Both the genome and native plasmid pCXC100 harbor a truncated toxin-antitoxin cassette that is precisely fused with a 5′-truncated IS
1237
sequence at one nonperfect repeat, indicating that it is a hot site for DNA rearrangement. Nevertheless, no transposition activity was detected when the putative transposase of IS
1237
was overexpressed in
Escherichia coli
. Using thermal asymmetric interlaced PCR, we identified 13 upstream and 10 downstream unique flanking sequences, and two pairs of these sequences were from the same loci, suggesting that IS
1237
has up to 65 unique loci in the
L. xyli
subsp.
cynodontis
chromosome. The presence of TAA or TTA direct repeat sequences at most insertion sites indicated that IS
1237
inserts into the loci by active transposition. IS
1237
showed a high propensity for insertion into other IS elements, such as IS
Lxc1
and IS
Lxc2
, which could offer IS
1237
a nonautonomous transposition pathway through the host IS elements. Interestingly, we showed that IS
1237
has a strong promoter at the 3′ end and a weak promoter at the 5′ end, and both promoters promote the transcription of adjacent genes in different gram-positive bacteria. The high-copy-number nature of IS
1237
and its promoter activity may contribute to bacterial fitness.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
11 articles.
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