Investigating the molecular basis for Rubisco acclimation to increasing temperature

假设：多亚基Rubisco酶的蛋白质异构体组成随环境温度的变化而变化。这开启了Rubisco工程可以用于增加重要作物的地理范围和在全球变暖之后保障粮食安全的可能性。背景：核酮糖-1,5-二磷酸羧化酶（Rubisco）是地球上最丰富的酶，在将无机CO2转化为有机碳化合物的光合作用中起着关键作用。这个复杂的过程是地球上生命的基础，也是所有自然生态系统和人类食物链的基础。然而，像所有酶驱动的过程一样，二氧化碳固定是一个对温度敏感的过程，了解这一途径中的酶如何对全球气温上升做出反应，可能对农业（和藻类生物技术）具有重要意义。本项目旨在通过对酶复合物的特定修饰，建立Rubisco适应高温的机制。Rubisco是一种具有光合驱动羧化酶活性和破坏加氧酶活性的双功能酶。后者以温度依赖的方式降低光合效率，导致植物生产力下降。植物Rubisco有8个由叶绿体基因rbcL编码的大亚基和8个由核红细胞基因家族编码的小亚基。叶绿体rbcL是一个单拷贝基因，它确保产生相同的大亚基蛋白。然而，核红细胞基因的多个拷贝产生不相同的小亚基蛋白。拟南芥红细胞抗原基因的表达在不同温度下发生变化。此外，在C3到CAM的转换过程中，不同的晶体间胚红细胞基因不成比例地下调。此外，在不同温度下驯化后，菠菜rubisco表现出不同的动力学特征。在变化的条件下，植物中不同的红细胞表达谱和伴随的Rubisco特性导致人们提出，不同的红细胞基因编码的小亚基在微调Rubisco以适应不同的条件中起作用。观察表明，暴露于季节温度显著变化的植物可能通过改变其光合作用最佳值来适应外部条件，从而加强了这一点。研究目的是对光合系统的温度敏感性/弹性进行比较研究，特别关注一系列模式生物和作物中的Rubisco酶复合物。

HYPOTHESIS: Protein isoform composition of the multi-subunit Rubisco enzyme changes in response to environmental temperature. This opens the possibility that Rubisco engineering could be used to increase the geographical range of important crops and safeguard food security in the wake of global warming.BACKGROUND: Ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), the most abundant enzyme on earth, has a key function in photosynthetic conversion of inorganic CO2 into organic carbon compounds. This complex process is fundamental to life on earth and underpins all natural ecosystems and the human food chain. However, like all enzyme-driven processes, CO2 fixation is a temperature-sensitive process and an understanding of how enzymes in this pathway respond to rising global temperatures could have important implications in agriculture (and algal biotechnology). This project aims to establish the mechanism by which Rubisco acclimates to high temperatures through specific modifications to the enzyme complex.Rubisco is a bifunctional enzyme with photosynthesis-driving carboxylase activity and the subversive oxygenase activity. The latter decreases photosynthetic efficiency in a temperature-dependent fashion, leading to reduced plant productivity. Plant Rubisco has eight large subunits encoded by the chloroplast gene rbcL and eight small subunits encoded by a family of nuclear rbcS genes. The chloroplast rbcL is a single-copy gene, which ensures production of identical large-subunit proteins. However, multiple copies of nuclear rbcS genes produce nonidentical small-subunit proteins. Expression of Arabidopsis rbcS genes changes under a range of temperatures. Additionally, different Mesembryanthemum crystallinum rbcS genes are disproportionately down-regulated during C3 to CAM switch. Furthermore, rubisco of Spinacia oleracea displays different kinetic profiles after acclimation at different temperatures. Different rbcS expression profiles and attendant Rubisco properties in plants under changing conditions led to the proposal that different rbcS gene-encoded small subunits have a role in fine-tuning Rubisco to acclimate to different conditions. This is reinforced by observations suggesting that plants exposed to significant changes in seasonal temperature may acclimate by shifting their photosynthetic optimum to match the external conditions. The study objective is a comparative study of the temperature sensitivity/resilience of photosynthetic systems, with particular focus on the Rubisco enzyme complex in a range of model organisms and crops.