Picosynechococcus sp. PCC 7002 Transcriptome or Gene expression. Picosynechococcus sp. PCC 7002

Synechococcus sp. strain PCC 7002 is a unicellular, euryhaline cyanobacterium; it is a model organism for studies of cyanobacterial metabolism and has great potential for biotechnological applications. It exhibits an exceptional tolerance of high light irradiation and shows very rapid growth under optimal conditions. The habitats from which this and related organisms were isolated are subject to changes in several environmental factors, including light, nutrient supply, temperature, and salinity. In this study global transcriptome profiling via RNAseq has been used to perform a comparative and integrated study of global changes in transcript levels in cells grown at different temperatures, at different salinity and under mixotrophic conditions, when a metabolizable organic carbon source was present. Furthermore, the transcriptomes were investigated for cells that were subjected to a heat shock and that were exposed to oxidative stress. Lower growth temperatures caused relatively minor changes of the global transcriptome; the most prominent changes affected fatty acid desaturases. A heat shock caused severe changes of the global transcriptome pattern; transcripts for genes associated with major metabolic pathways declined and those for different chaperones increased dramatically. Oxidative stress, however, left the transcript pattern almost unaffected. Besides the increased expression of genes involved in compatible solute biosynthesis, Synechococcus sp. PCC 7002 showed increased mRNA levels for several genes involved in electron transport, which also generally increased under unfavorable growth conditions. Transcripts of two adjacent genes dramatically increased upon growth at high salinity; the respective proteins are putatively involved in coping with oxidative stress and in triggering ion channels. Only minor changes were observed when cells were grown at low salinity or when the growth medium was supplemented with glycerol. However, the transcriptome data suggest that cells must acclimate to excess reducing equivalents when a reduced C-source is present.

聚球藻属（Synechococcus sp.）菌株PCC 7002是一种单细胞、广盐性蓝细菌，是蓝细菌代谢研究的模式生物，在生物技术应用中具备巨大潜力。该菌株对强光照射具有卓越耐受性，在最优培养条件下生长速率极快。分离得到该菌株及近缘菌株的生境，其环境因子存在多重波动，涵盖光照、营养供给、温度与盐度等维度。本研究通过RNA测序（RNAseq）开展全局转录组分析，对在不同温度、不同盐度条件下以及添加可代谢有机碳源的混合营养条件下培养的细胞，其转录水平的全局变化进行了比较与整合研究。此外，本研究还针对经历热激处理与氧化应激暴露的细胞，开展了转录组分析。较低的生长温度仅对全局转录组造成相对轻微的调控变化，其中最显著的差异涉及脂肪酸去饱和酶相关基因。热激处理则会引发全局转录组模式的剧烈改变：参与核心代谢途径的基因转录本水平显著下调，而各类分子伴侣编码基因的转录本则大幅上调。与之相反，氧化应激几乎未对细胞转录模式造成显著影响。除相容性溶质生物合成相关基因的表达上调外，聚球藻属菌株PCC 7002中多个参与电子传递过程的基因的mRNA水平也有所提升，这类基因在不利生长条件下通常也会呈现表达上调趋势。在高盐度培养条件下，两个相邻基因的转录本水平显著升高，其编码的蛋白推测分别参与氧化应激应对与离子通道激活过程。当细胞在低盐度条件下培养，或培养基中添加甘油时，仅能观测到轻微的转录组变化。但转录组数据分析结果显示，当培养体系中存在还原态碳源时，细胞需要对过量积累的还原当量进行适应性调控。