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Light Response of Pseudomonas putida KT2440 Mediated by Class II LitR, a Photosensor Homolog
KT2440 retains three homologs (PplR1 to PplR3) of the LitR/CarH family, an adenosyl B -dependent light-sensitive MerR family transcriptional regulator. Transcriptome analysis revealed the existence of a number of photoinducible genes, including , (encoding DNA photolyase), (furan-containing fatty ac...
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Published in: | Journal of bacteriology 2020-09, Vol.202 (20) |
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Main Authors: | , , , , , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | KT2440 retains three homologs (PplR1 to PplR3) of the LitR/CarH family, an adenosyl B
-dependent light-sensitive MerR family transcriptional regulator. Transcriptome analysis revealed the existence of a number of photoinducible genes, including
,
(encoding DNA photolyase),
(furan-containing fatty acid synthase),
(GTP cyclohydrolase I),
(cryptochrome-like protein), and multiple genes without annotated/known function. Transcriptional analysis by quantitative reverse transcription-PCR with knockout mutants of
to
showed that a triple knockout completely abolished the light-inducible transcription in
, which indicates the occurrence of ternary regulation of PplR proteins. A DNase I footprint assay showed that PplR1 protein specifically binds to the promoter regions of light-inducible genes, suggesting a consensus PplR1-binding direct repeat, 5'-T(G/A)TACAN
TGTA(C/T)A-3'. The disruption of B
biosynthesis cluster did not affect the light-inducible transcription; however, disruption of
(where LOV indicates "light, oxygen, or voltage") and
, encoding blue light photoreceptors adjacently located to
and
, respectively, led to the complete loss of light-inducible transcription. Overall, the results suggest that the three PplRs and two PpSB-LOVs cooperatively regulate the light-inducible gene expression. The wide distribution of the
/
cognate pair homologs in
spp. and related bacteria suggests that the response and adaptation to light are similarly regulated in the group of nonphototrophic bacteria.
The LitR/CarH family is a new group of photosensor homologous to MerR-type transcriptional regulators. Proteins of this family are distributed to various nonphototrophic bacteria and grouped into at least five classes (I to V).
retaining three class II LitR proteins exhibited a genome-wide response to light. All three paralogs were functional and mediated photodependent activation of promoters directing the transcription of light-induced genes or operons. Two LOV (light, oxygen, or voltage) domain proteins, adjacently encoded by two
genes, were also essential for the photodependent transcriptional control. Despite the difference in light-sensing mechanisms, the DNA binding consensus of class II LitR [T(G/A)TA(C/T)A] was the same as that of class I. This is the first study showing the actual involvement of class II LitR in light-induced transcription. |
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ISSN: | 0021-9193 1098-5530 |
DOI: | 10.1128/JB.00146-20 |