Carbon metabolism in sink limited conditions

未来五年，我们将继续研究春季短命植物碳（C）代谢的调控。1)春季短命植物在低温下比在高温下产生更大的贮藏器官（鳞茎或球茎），这是温带物种中的一个独特情况。然而，这些器官的碳代谢也呈现出与其他主要汇，如马铃薯块茎或谷物的碳代谢的相似性。蛋白质组学方法将被用来确定的主要蛋白质的存储器中的生长温度调制。那些与C代谢关系更密切的蛋白质将被进一步研究。2)春季短命植物的叶片衰老显然是由反馈抑制一旦库生长放缓。淀粉不积累在这些物种的叶子，反馈抑制似乎使用一个不同的途径比一个已经描述的淀粉积累物种。我们将尝试使用不同的方法来识别导致叶片衰老的级联事件：体内叶绿素荧光，气体交换和蛋白质组学。3)分配到球茎细胞壁物质中的C随生长温度的升高而增加。这可能是一种在淀粉储存能力降低的条件下转移一些C并避免反馈抑制的方法。我们将分析细胞壁的组成和测试的假设，半纤维素被用作碳水化合物储存库时，库的增长放缓。呼吸率-通过细胞色素和替代途径-也将作为另一种途径进行监测，在生长受到汇活动限制的情况下，这种途径可以使用额外的碳。对春季短命植物碳代谢的研究将有助于揭示一些使它们在低温下达到大尺寸的机制。这项研究也将导致更好地了解碳代谢的调节在汇有限的物种，即在碳水化合物过量的条件下，这种情况下，物种将遇到更经常在未来的CO2浓度继续增加。

In the next five years, we will continue to study the regulation of carbon (C) metabolism in spring ephemerals. 1) Spring ephemerals produce much larger storage organs (bulb or corm) under low than under higher growth temperature, a unique case amongst temperate species. However, the C metabolism of these organs also presents similarities with the C metabolism of other major sinks such as potato tuber or cereal grain. A proteomic approach will be used to identify the main proteins in the storage organ that are modulated by growth temperature. Those proteins more closely related to C metabolism will be further studied. 2) Leaf senescence in spring ephemerals is apparently induced by feedback inhibition once sink growth has slowed down. Starch does not accumulate in the leaves of these species; feedback inhibition appears to use a different pathway than the one already described for starch accumulating species. We will try to identify the cascade of events leading to leaf senescence using different approaches: in vivo chlorophyll fluorescence, gas exchanges, and proteomics. 3) C partitioned to cell wall material in the corms increases with growth temperature. This could be a way to divert some of the C and avoid feedback inhibition under conditions of reduced starch storage capacity. We will analyse cell wall composition and test the hypothesis that hemicelluloses are used as carbohydrate storages when sink growth slows down. Respiratory rates - both through the cytochrome and the alternative pathways - will also be monitored as another pathway that can use extra C in conditions where growth becomes limited by sink activity. Study of the C metabolism of spring ephemerals will help unravel some of the mechanisms that allow them to reach large sizes under low temperatures. This study will also lead to a better understanding of the regulation of C metabolism in sink limited species, i.e. in conditions where carbohydrates are in excess, a situation that species will encounter more often in the future as CO2 concentrations continue to increase.