ABSTRACT

Anoxygenic photosynthesis is an important pathway for Rhodobacter sphaeroides to produce ATP under oxygen-limiting conditions. The expression of its photosynthesis genes is tightly regulated at transcriptional and post-transcriptional levels in response to light and oxygen signals, to avoid photooxidative stress by the simultaneous presence of pigments, light and oxygen. The puf operon encodes pigment-binding proteins of the light-harvesting complex I (genes pufB and pufA), of the reaction centre (genes pufL and pufM), a scaffold protein (gene pufX) and includes the gene for sRNA PcrX. Segmental differences in the stability of the pufBALMX-pcrX mRNA contribute to the stoichiometry of LHI to RC complexes. With asPcrL we identified the third sRNA and the first antisense RNA that is involved in balancing photosynthesis gene expression in R. sphaeroides. asPcrL influences the stability of the pufBALMX-pcrX mRNA but not of the pufBA mRNA and consequently the stoichiometry of photosynthetic complexes. By base pairing to the pufL region asPcrL promotes RNase III-dependent degradation of the pufBALMX-prcX mRNA. Since asPcrL is activated by the same protein regulators as the puf operon including PcrX it is part of an incoherent feed-forward loop that fine-tunes photosynthesis gene expression.

Graphical Abstract

摘要

无氧光合作用是球形红杆菌在限氧条件下产生ATP的重要途径。其光合作用基因的表达在转录和转录后水平受到光和氧信号的严格调节，以避免同时存在色素、光和氧而产生光氧化应激。puf操纵子编码光捕获复合物 I（基因pufB和pufA）、反应中心（基因pufL和pufM）、支架蛋白（基因pufX ）的色素结合蛋白，并包括 sRNA PcrX 基因。pufBALMX-pcrX稳定性的分段差异mRNA 有助于 LHI 与 RC 复合物的化学计量。使用asPcrL，我们鉴定了第三种 sRNA 和第一种参与平衡球状红球菌中光合作用基因表达的反义 RNA 。asPcrL 影响pufBALMX-pcrX mRNA 的稳定性，但不影响pufBA mRNA 的稳定性，因此影响光合复合物的化学计量。通过与pufL区域的碱基配对，asPcrL 促进了pufBALMX-prcX mRNA的 RNase III 依赖性降解。由于 asPcrL 由与puf操纵子（包括 PcrX）相同的蛋白质调节剂激活，它是微调光合作用基因表达的不连贯前馈循环的一部分。

图形概要

图形概要