Petersen Jörn, Brinkmann Henner, Cerff Rüdiger
Institute of Genetics, University of Braunschweig, D-38106 Braunschweig, Germany.
J Mol Evol. 2003 Jul;57(1):16-26. doi: 10.1007/s00239-002-2441-y.
NAD-specific glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a cytosolic marker enzyme of eukaryotes (GapC; EC 1.2.1.12). Land plants possess an additional NADP+-dependent enzyme (EC 1.2.1.13) within their chloroplasts which is composed of two subunits, GapA and GapB. Another plastid GAPDH enzyme (GapCp) was recently discovered in gymnosperms and ferns. This novel GapCp is closely related to cytosolic GapC and displays glycolytic NAD+ cosubstrate specificity. Here we show that this new gene GapCp is also present and actively expressed in angiosperms, mosses, and liverworts. Phylogenetic analyses of the available GapC and GapCp sequences suggest that the gene duplication giving rise to GapCp occurred in ancestral charophyte algae. The data are also consistent with a monophyletic origin of charophytes and land plants and further support the view that land plants arose from a Coleochaete-like green alga. Northern hybridizations were employed to study the expression of the genes GapCp, GapC, GapA, and GapB in green and nongreen tissues from pepper (Capsicum annuum). The results demonstrate that GapCp mRNAs are mainly expressed in red pepper fruit and roots, in which the transcript levels of photosynthetic GapA and GapB are downregulated. This suggests that in flowering plants GapCp plays a specific role in glycolytic energy production of nongreen plastids such as chromoplasts and leukoplasts and that angiosperms may be the only land plants where glycolysis is absent in green chloroplasts.
NAD特异性甘油醛-3-磷酸脱氢酶（GAPDH）是真核生物的一种胞质标记酶（GapC；EC 1.2.1.12）。陆地植物在其叶绿体中还拥有一种额外的依赖NADP⁺的酶（EC 1.2.1.13），它由两个亚基GapA和GapB组成。最近在裸子植物和蕨类植物中发现了另一种质体GAPDH酶（GapCp）。这种新的GapCp与胞质GapC密切相关，并表现出糖酵解NAD⁺共底物特异性。在这里我们表明，这个新基因GapCp在被子植物、苔藓和地钱中也存在并活跃表达。对现有GapC和GapCp序列的系统发育分析表明，产生GapCp的基因复制发生在祖先轮藻中。这些数据也与轮藻和陆地植物的单系起源一致，并进一步支持了陆地植物起源于类似鞘毛藻的绿藻这一观点。采用Northern杂交技术研究了辣椒（Capsicum annuum）绿色和非绿色组织中GapCp、GapC、GapA和GapB基因的表达。结果表明，GapCp mRNA主要在红辣椒果实和根中表达，其中光合GapA和GapB的转录水平下调。这表明在开花植物中，GapCp在非绿色质体如有色体和白色体的糖酵解能量产生中起特定作用，并且被子植物可能是绿色叶绿体中不存在糖酵解的唯一陆地植物。
