Recent progress in metabolic engineering has led to autotrophic production of ethanol in various cyanobacterial hosts. However, cyanobacteria are known to be sensitive to ethanol, which restricts further efforts to increase ethanol production levels in these renewable host systems. To understand the mechanisms of ethanol tolerance so that engineering more robust cyanobacterial hosts can be possible, in this study, the responses of model cyanobacterial Synechocystis sp. PCC 6803 to ethanol were determined using a quantitative proteomics approach with iTRAQ LC-MS/MS technologies. The resulting high-quality proteomic data set consisted of 24,887 unique peptides corresponding to 1509 identified proteins, a coverage of approximately 42% of the predicted proteins in the Synechocystis genome. Using a cutoff of 1.5-fold change and a p-value less than 0.05, 135 and 293 unique proteins with differential abundance levels were identified between control and ethanol-treated samples at 24 and 48 h, respectively. Functional analysis showed that the Synechocystis cells employed a combination of induced common stress response, modifications of cell membrane and envelope, and induction of multiple transporters and cell mobility-related proteins as protection mechanisms against ethanol toxicity. Interestingly, our proteomic analysis revealed that proteins related to multiple aspects of photosynthesis were up-regulated in the ethanol-treated Synechocystis cells, consistent with increased chlorophyll a concentration in the cells upon ethanol exposure. The study provided the first comprehensive view of the complicated molecular mechanisms against ethanol stress and also provided a list of potential gene targets for further engineering ethanol tolerance in Synechocystis PCC 6803.

BackgroundFermentation production of biofuel ethanol consumes agricultural crops, which will compete directly with the food supply. As an alternative, photosynthetic cyanobacteria have been proposed as microbial factories to produce ethanol directly from solar energy and CO2. However, the ethanol productivity from photoautotrophic cyanobacteria is still very low, mostly due to the low tolerance of cyanobacterial systems to ethanol stress.ResultsTo build a foundation necessary to engineer robust ethanol-producing cyanobacterial hosts, in this study we applied a quantitative transcriptomics approach with a next-generation sequencing technology, combined with quantitative reverse-transcript PCR (RT-PCR) analysis, to reveal the global metabolic responses to ethanol in model cyanobacterial Synechocystis sp. PCC 6803. The results showed that ethanol exposure induced genes involved in common stress responses, transporting and cell envelope modification. In addition, the cells can also utilize enhanced polyhydroxyalkanoates (PHA) accumulation and glyoxalase detoxication pathway as means against ethanol stress. The up-regulation of photosynthesis by ethanol was also further confirmed at transcriptional level. Finally, we used gene knockout strains to validate the potential target genes related to ethanol tolerance.ConclusionRNA-Seq based global transcriptomic analysis provided a comprehensive view of cellular response to ethanol exposure. The analysis provided a list of gene targets for engineering ethanol tolerance in cyanobacterium Synechocystis.

BackgroundPhotosynthetic cyanobacteria have been recently proposed as a ‘microbial factory’ to produce butanol due to their capability to utilize solar energy and CO2 as the sole energy and carbon sources, respectively. However, to improve the productivity, one key issue needed to be addressed is the low tolerance of the photosynthetic hosts to butanol.ResultsIn this study, we first applied a quantitative transcriptomics approach with a next-generation RNA sequencing technology to identify gene targets relevant to butanol tolerance in a model cyanobacterium Synechocystis sp. PCC 6803. The results showed that 278 genes were induced by the butanol exposure at all three sampling points through the growth time course. Genes encoding heat-shock proteins, oxidative stress related proteins, transporters and proteins involved in common stress responses, were induced by butanol exposure. We then applied GC-MS based metabolomics analysis to determine the metabolic changes associated with the butanol exposure. The results showed that 46 out of 73 chemically classified metabolites were differentially regulated by butanol treatment. Notably, 3-phosphoglycerate, glycine, serine and urea related to general stress responses were elevated in butanol-treated cells. To validate the potential targets, we constructed gene knockout mutants for three selected gene targets. The comparative phenotypic analysis confirmed that these genes were involved in the butanol tolerance.ConclusionThe integrated OMICS analysis provided a comprehensive view of the complicated molecular mechanisms employed by Synechocystis sp. PCC 6803 against butanol stress, and allowed identification of a series of potential gene candidates for tolerance engineering in cyanobacterium Synechocystis sp. PCC 6803.

The pentatricopeptide repeat (PPR) family plays a major role in RNA stability, regulation, processing, splicing, translation, and editing. Leucine-rich PPR-motif-containing protein (LRPPRC), a member of the PPR family, is a known gene mutation that causes Leigh syndrome French–Canadian. Recently, growing evidence has pointed out that LRPPRC dysregulation is related to various diseases ranging from tumors to viral infections. This review presents available published data on the LRPPRC protein function and its role in tumors and other diseases. As a multi-functional protein, LRPPRC regulates a myriad of biological processes, including energy metabolism and maturation and the export of nuclear mRNA. Overexpression of LRPPRC has been observed in various human tumors and is associated with poor prognosis. Downregulation of LRPPRC inhibits growth and invasion, induces apoptosis, and overcomes drug resistance in tumor cells. In addition, LRPPRC plays a potential role in Parkinson's disease, neurofibromatosis 1, viral infections, and venous thromboembolism. Further investigating these new functions of LRPPRC should provide novel opportunities for a better understanding of its pathological role in diseases from tumors to viral infections and as a potential biomarker and molecular target for disease treatment.

Fyn, a member of the Src family of tyrosine kinases, is a key regulator in cytoskeletal remodeling in a variety of cell types. Recent studies have demonstrated that Fyn is responsible for nephrin tyrosine phosphorylation, which will result in polymerization of actin filaments and podocyte damage. Thus detailed involvement of Fyn in podocytes is to be elucidated. In this study, we investigated the potential role of Fyn/ROCK signaling and its interactions with paxillin. Our results presented that high glucose led to filamentous actin (F-actin) rearrangement in podocytes, accompanied by paxillin phosphorylation and increased cell motility, during which Fyn and ROCK were markedly activated. Gene knockdown of Fyn by siRNA showed a reversal effect on high glucose-induced podocyte damage and ROCK activation; however, inhibition of ROCK had no significant effects on Fyn phosphorylation. These observations demonstrate that in vitro Fyn mediates high glucose-induced actin cytoskeleton remodeling of podocytes via promoting ROCK activation and paxillin phosphorylation.

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) is one of the most important indigenous tree species in China. Owing to their rapid growth, good timber quality and short rotation time, increasing numbers of plantations are being established with successive rotations. Numerous competing hypotheses have been described to explain the decline in yield that occurs with successive rotations of the plantations. In addition, there are some uncertainties regarding the changes and characteristics of biomass carbon pools in Chinese fir forests in subtropical China, and information is lacking regarding how to improve carbon sequestration by this biomass sink. The total biomass carbon stock of the Chinese fir forest in China increased from 91.57 Tg C in 1977Á1981 to 238.50 Tg C in 2004Á2008, accounting for 2.48Á4.32% of the national forest biomass carbon in the corresponding period. Due to the decreased yield during successive rotation for Chinese fir plantations before the 1990s, the biomass carbon stock of Chinese fir forests decreased in several regions in China during the 1980s and 1990s, and increased in the 2000s when several silvicultural measures were implemented to improving the quality of Chinese fir plantations. When compared with the age-based volume to biomass (VÁB) method of determining biomass carbon stock in Chinese fir forests in Jiangxi Province, the site specific-based and the mixed forests-based scenarios would both help offset CO 2 emissions by sequestrating more CO 2 from the atmosphere.

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