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会随着环境温度的变化而变化。这为在全球变暖的情况下利用Rubisco工程扩大重要农作物的地理范围和保障粮食安全提供了可能性。背景：核酮糖-1，5-二磷酸羧基加氧酶(Rubisco)是地球上含量最丰富的酶，在无机二氧化碳光合作用转化为有机碳化合物的过程中起着关键作用。这一复杂的过程是地球上生命的基础，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温度敏感的过程，了解这一途径中的酶如何响应全球气温上升可能对农业(和藻类生物技术)具有重要意义。该项目旨在通过对酶复合体的特定修饰来建立Rubisco适应高温的机制。Rubisco是一种双功能酶，具有光合作用驱动的羧基酶活性和颠覆性的加氧酶活性。后者以依赖温度的方式降低光合作用效率，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Rbcs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副本会产生不同的小亚基蛋白。拟南芥RBC基因的表达在一定的温度范围内发生变化。此外，不同的中胚性结晶性红细胞基因在C3到CAM的转换过程中有不成比例的下调。此外，在不同温度下驯化后的菠菜Rubisco表现出不同的动力学特征。不同条件下植物中不同的Rbcs表达谱和伴随的Rubisco特性导致了不同的Rbcs基因编码的小亚基在微调Rubisco以适应不同条件方面的作用。观察表明，暴露在季节性温度显著变化中的植物可能会通过改变其最适光合作用来适应外部条件，这一点得到了加强。这项研究的目的是比较研究光合作用系统的温度敏感性/弹性，特别是在一系列模式生物和作物中的Rubisco酶复合体。

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.