Carbon metabolism in sink limited conditions

未来5年，我们将继续研究春季植物碳(C)代谢的调控。1)春季短生植物在较低的生长温度下比在较高的生长温度下产生更大的贮藏器官（球茎或球茎），这在温带物种中是独特的。然而，这些器官的碳代谢也与马铃薯块茎或谷物等其他主要碳汇的碳代谢有相似之处。蛋白质组学方法将用于鉴定受生长温度调节的储存器官中的主要蛋白质。那些与C代谢密切相关的蛋白将被进一步研究。2)春季短生植物叶片衰老明显是由于汇生长放缓后的反馈抑制引起的。淀粉不会在这些植物的叶子中积累；反馈抑制似乎使用了一种不同的途径，而不是已经描述的淀粉积累物种。我们将尝试使用不同的方法来确定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)随着生长温度的升高，球茎内分配给细胞壁物质的碳含量逐渐增加。这可能是一种在淀粉储存能力降低的情况下转移部分C和避免反馈抑制的方法。我们将分析细胞壁组成，并验证当碳汇生长减缓时半纤维素被用作碳水化合物储存的假设。呼吸速率——通过细胞色素和其他途径——也将被监测，作为另一种途径，在生长受到汇活性限制的情况下，可以使用额外的C。对春季蜉蝣的C代谢的研究将有助于揭示使它们在低温下达到大尺寸的一些机制。本研究还将有助于更好地了解碳汇受限物种（即碳水化合物过量的物种）对碳代谢的调节，随着二氧化碳浓度的持续增加，碳水化合物过量的物种将在未来更频繁地遇到这种情况。

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.