Impact of microcystin on RubisCO and the carbon concentrating mechanism of Microcystis aeruginosa

我们最近的研究结果首次显示了毒素微囊藻毒素对宿主细胞的重要细胞内功能。特别是，微囊藻毒素对微囊藻适应和驯化变化的无机碳水平有影响。分子生物学研究为微囊藻毒素与RubisCO的相互作用以及微囊藻毒素对不同碳酸氢盐转运蛋白基因转录的影响提供了证据。目前的项目旨在剖析微囊藻毒素在这些过程中的作用，在体外和体内。我们具体计划测试以下假设：1）微囊藻毒素作为调节因子并影响RubisCO的羧化和氧合反应之间的比率，2）微囊藻毒素特异性地稳定羧化体外RubisCO部分，从而促进胞质溶胶中的氧合反应，3）微囊藻毒素影响RubisCO在羧化体和胞质溶胶之间的分配，4）不同的微囊藻生态型不仅在它们的碳酸氢根吸收基因的含量上不同，而且显示出调节碳酸氢根转运蛋白转录的串扰，5）有毒和无毒菌株在特定光下的碳酸氢盐摄取活性不同。pCO2条件导致不同CCM活动。该项目旨在深入了解微囊藻对无机碳的适应以及微囊藻毒素的作用。了解微囊藻的生活方式将是其他水华蓝藻的代表，因此可能有助于蓝藻水华的新的管理策略的发展。

Our recent findings have shown for the first time an important intracellular function of the toxin microcystin for the host cell. Particularly, microcystin has an impact on the adaptation and acclimation of Microcystis to changing inorganic carbon levels. Molecular studies provided evidence for an interaction of microcystin with RubisCO and an influence of (extracellular) microcystin on the transcription of different bicarbonate transporter genes. The current project aims to dissect the role of microcystin in these processes in vitro and in vivo. We are specifically planning to test the following hypotheses:1) Microcystin acts as a regulatory factor and influences the ratio between the carboxylation and the oxygenation reaction of RubisCO,2) Microcystin specifically stabilizes the extra-carboxysomal RubisCO portion and thereby promotes the oxygenation reaction in the cytosol, 3) Microcystin affects the partitioning of RubisCO between carboxysomes and cytosol, 4) Distinct Microcystis ecotypes differ not only in their content of genes for bicarbonate uptake but show a cross-talk regulating bicarbonate transporter transcription,5) Toxic and non-toxic strains differ in the bicarbonate uptake activities under specific light/ pCO2 conditions leading to different CCM activities.The project aims to provide deeper insights into the inorganic carbon adaptation of Microcystis and the role of microcystin. Understanding the life style of Microcystis will be representative for other bloom-forming cyanobacteria and may thus contribute to the development of new management strategies for cyanobacterial blooms.