Abstract
Small regulatory RNAs (sRNAs) function as transcriptional and post-transcriptional regulators of gene expression in organisms from all domains of life. Cyanobacteria are thought to have developed a complex RNA-based regulatory mechanism. In the current study, by genome-wide analysis of differentially expressed small RNAs in Synechocystis sp. PCC 6803 under high light conditions, we discovered an asRNA (RblR) that is 113nt in length and completely complementary to its target gene rbcL, which encodes the large chain of RuBisCO, the enzyme that catalyzes carbon fixation. Further analysis of the RblR(+)/(−) mutants revealed that RblR acts as a positive regulator of rbcL under various stress conditions; Suppressing RblR adversely affects carbon assimilation and thus the yield, and those phenotypes of both the wild type and the overexpressor could be downgraded to the suppressor level by carbonate depletion, indicated a regulatory role of RblR in CO2 assimilation. In addition, a real-time expression platform in Escherichia coli was setup and which confirmed that RblR promoted the translation of the rbcL mRNA into the RbcL protein. The present study is the first report of a regulatory RNA that targets RbcL in Synechocystis sp. PCC 6803, and provides strong evidence that RblR regulates photosynthesis by positively modulating rbcL expression in Synechocystis.
Highlights
Small regulatory RNAs are key genetic regulators in organisms from all domains of life
Using the dRNA-Seq protocol (Sharma et al, 2010), we isolated total RNA from cells cultivated under normal light (NL) or high light (HL) conditions and used this RNA to prepare cDNA libraries enriched for primary transcripts
Chl fluorescence was measured with a Dual-PAM-100 Chl fluorescence photosynthesis analyzer (Walz, Germany) using 3 ml culture, grown under NL or -C conditions for 8 h at room temperature in darkness, according to the manufacturer’s instructions, at which point the cells were in the exponential growth phase
Summary
Small regulatory RNAs (sRNAs) are key genetic regulators in organisms from all domains of life In bacteria, these regulatory RNAs are generally referred to as sRNAs, because they usually range from 50 to 500 nt in length (Gottesman and Storz, 2011). These regulatory RNAs are generally referred to as sRNAs, because they usually range from 50 to 500 nt in length (Gottesman and Storz, 2011) These sRNAs control a variety of processes, including chromosome maintenance (Storz, 2002; Volpe et al, 2002), the stability and translation of mRNAs (Storz et al, 2004), the stability and translocation of proteins (Huttenhofer et al, 2005; Hüttenhofer and Vogel, 2006), stress responses (Romby et al, 2006), metabolic reactions (Park et al, 2010), and pathogenesis (Lee and Groisman, 2010). Cis-encoded antisense sRNAs (asRNAs) that are located on the strand of DNA opposite their mRNA targets, exhibit extensive complementarity to their
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