Interactions of C4 subtype metabolic activities and transport in maize are revealed through the characterization of DCT2 mutants.
Interactions of C4 subtype metabolic activities and transport in maize are revealed through the characterization of DCT2 mutants.
复制标题
通过 DCT2 突变体的表征揭示了玉米中 C4 亚型代谢活动和转运的相互作用。
DOI：
10.1105/tpc.15.00497
复制
发表时间：
2016
期刊：
影响因子：
11.6
通讯作者：
Brutnell TP.
中科院分区：
文献类型：
--
作者：
Weissmann S;Ma F;Furuyama K;Gierse J;Berg H;Shao Y;Taniguchi M;Allen DK;Brutnell TP.
禾本科植物的C4光合作用需要代谢产物通过叶肉和维管束鞘两种特殊的叶细胞进行协调运动，以将CO2聚集在Rubisco周围。尽管转运蛋白在这一过程中的重要性，很少有被确定或严格的特点。在玉米（Zea mays）中，DCT 2被认为是一种定位于质体的苹果酸转运蛋白，并优先在BS细胞中表达。在这里，我们使用Activator标记的突变等位基因来表征DCT2在玉米叶片中的作用。我们的结果表明，DCT 2使苹果酸运输到BS叶绿体。同位素标记实验表明，DCT2的丢失导致代谢网络的运作明显不同，生物量的生产显着减少。在没有苹果酸穿梭的情况下，dct2系通过增强磷酸烯醇丙酮酸羧激酶碳穿梭途径的使用而存活，在野生型玉米中，磷酸烯醇丙酮酸羧激酶碳穿梭途径占光合活性的约25%。这些结果强调了C4光合作用过程中苹果酸运输的重要性，定义了BS细胞中初级苹果酸转运蛋白的作用，并支持了玉米BS和M细胞之间的碳交换模型。
C4photosynthesis in grasses requires the coordinated movement of metabolites through two specialized leaf cell types, mesophyll (M) and bundle sheath (BS), to concentrate CO2around Rubisco. Despite the importance of transporters in this process, few have been identified or rigorously characterized. In maize (Zea mays),DCT2has been proposed to function as a plastid-localized malate transporter and is preferentially expressed in BS cells. Here, we characterized the role ofDCT2in maize leaves usingActivator-tagged mutant alleles. Our results indicate thatDCT2enables the transport of malate into the BS chloroplast. Isotopic labeling experiments show that the loss ofDCT2results in markedly different metabolic network operation and dramatically reduced biomass production. In the absence of a functioning malate shuttle,dct2lines survive through the enhanced use of the phosphoenolpyruvate carboxykinase carbon shuttle pathway that in wild-type maize accounts for ∼25% of the photosynthetic activity. The results emphasize the importance of malate transport during C4photosynthesis, define the role of a primary malate transporter in BS cells, and support a model for carbon exchange between BS and M cells in maize.