Life Science Research Center, College of Bioresource Sciences, Nihon University, Tokyo, Japan.
Applied Chemistry and Biochemical Engineering Course, Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, Hamamatsu, Shizuoka, Japan.
J Bacteriol. 2020 Sep 23;202(20). doi: 10.1128/JB.00146-20.
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)TACANTGTA(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.
KT2440 保留了三个同源物（PplR1 到 PplR3），属于腺苷基 B 依赖性光敏感 MerR 家族转录调节因子。转录组分析显示存在许多光诱导基因，包括 （编码 DNA 光解酶）、 （含呋喃的脂肪酸合酶）、 （GTP 环化水解酶 I）、 （隐色体样蛋白）和多个没有注释/已知功能的基因。通过定量逆转录-PCR 对 到 的敲除突变体进行转录分析表明，三重敲除完全消除了 中的光诱导转录，这表明 PplR 蛋白发生了三元调节。DNase I 足迹测定表明，PplR1 蛋白特异性结合于光诱导基因的启动子区域，表明存在 PplR1 结合的直接重复序列，5'-T(G/A)TACANTGTA(C/T)A-3'。B 生物合成簇的破坏并不影响光诱导转录；然而，破坏 （其中 LOV 表示“光、氧或电压”）和 ，分别编码与 相邻的蓝光光受体，导致光诱导转录完全丧失。总的来说，结果表明，三个 PplR 和两个 PpSB-LOV 协同调节光诱导基因表达。/ 同源物对在 spp. 及其相关细菌中的广泛分布表明，非光合细菌群体中对光的响应和适应受到类似的调节。LitR/CarH 家族是 MerR 型转录调节因子的新型光传感器同源物。该家族的蛋白质分布在各种非光合细菌中，并分为至少五个类（I 到 V）。保留三个 II 类 LitR 蛋白的 表现出对光的全基因组响应。三个旁系同源物都是功能性的，并介导光依赖性启动子激活，指导光诱导基因或操纵子的转录。两个 LOV（光、氧或电压）结构域蛋白，由两个 基因邻接编码，对于光依赖性转录控制也是必需的。尽管光感应机制不同，但 II 类 LitR 的 DNA 结合共识 [T(G/A)TA(C/T)A]与 I 类相同。这是首次表明 II 类 LitR 实际参与光诱导转录的研究。
