BACKGROUND The tricarboxylic acid (TCA) cycle is crucial for cellular energy metabolism and carbon skeleton supply. However, the detailed functions of the maize TCA cycle genes remain unclear. RESULTS In this study, 91 TCA genes were identified in maize by a homology search, and they were distributed on 10 chromosomes and 1 contig. Phylogenetic results showed that almost all maize TCA genes could be classified into eight major clades according to their enzyme families. Sequence alignment revealed that several genes in the same subunit shared high protein sequence similarity. The results of cis-acting element analysis suggested that several TCA genes might be involved in signal transduction and plant growth. Expression profile analysis showed that many maize TCA cycle genes were expressed in specific tissues, and replicate genes always shared similar expression patterns. Moreover, qPCR analysis revealed that some TCA genes were highly expressed in the anthers at the microspore meiosis phase. In addition, we predicted the potential interaction networks among the maize TCA genes. Next, we cloned five TCA genes located on different TCA enzyme complexes, Zm00001d008244 (isocitrate dehydrogenase, IDH), Zm00001d017258 (succinyl-CoA synthetase, SCoAL), Zm00001d025258 (α-ketoglutarate dehydrogenase, αKGDH), Zm00001d027558 (aconitase, ACO) and Zm00001d044042 (malate dehydrogenase, MDH). Confocal observation showed that their protein products were mainly localized to the mitochondria; however, Zm00001d025258 and Zm00001d027558 were also distributed in the nucleus, and Zm00001d017258 and Zm00001d044042 were also located in other unknown positions in the cytoplasm. Through the bimolecular fluorescent complimentary (BiFC) method, it was determined that Zm00001d027558 and Zm00001d044042 could form homologous dimers, and both homologous dimers were mainly distributed in the mitochondria. However, no heterodimers were detected between these five genes. Finally, Arabidopsis lines overexpressing the above five genes were constructed, and those transgenic lines exhibited altered primary root length, salt tolerance, and fertility. CONCLUSION Sequence compositions, duplication patterns, phylogenetic relationships, cis-elements, expression patterns, and interaction networks were investigated for all maize TCA cycle genes. Five maize TCA genes were overexpressed in Arabidopsis, and they could alter primary root length, salt tolerance, and fertility. In conclusion, our findings may help to reveal the molecular function of the TCA genes in maize.

中文翻译：

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玉米中TCA循环基因的鉴定和表征。

背景技术三羧酸（TCA）循环对于细胞能量代谢和碳骨架供应至关重要。然而，玉米TCA循环基因的详细功能仍不清楚。结果在这项研究中，通过同源搜索在玉米中鉴定出91个TCA基因，它们分布在10条染色体和1个重叠群上。系统发育结果表明，几乎所有玉米TCA基因都可以根据其酶家族分为8个主要进化枝。序列比对揭示同一亚基中的几个基因共享高蛋白序列相似性。顺式作用元件分析的结果表明，几个TCA基因可能参与信号转导和植物生长。表达谱分析表明，许多玉米TCA循环基因在特定组织中表达，复制基因总是共享相似的表达模式。此外，qPCR分析显示在小孢子减数分裂期的花药中某些TCA基因高表达。另外，我们预测了玉米TCA基因之间的潜在相互作用网络。接下来，我们克隆了位于不同TCA酶复合体上的五个TCA基因，Zm00001d008244（异柠檬酸脱氢酶，IDH），Zm00001d017258（琥珀酰-CoA合成酶，SCoAL），Zm00001d025258（α-酮戊二酸脱氢酶，αKGDH），Zm00001d027558（acom） （苹果酸脱氢酶，MDH）。共聚焦观察表明，它们的蛋白质产物主要定位于线粒体。但是，Zm00001d025258和Zm00001d027558也分布在原子核中，Zm00001d017258和Zm00001d044042也位于细胞质的其他未知位置。通过双分子荧光互补法（BiFC），确定Zm00001d027558和Zm00001d044042可以形成同源二聚体，并且两个同源二聚体主要分布在线粒体中。但是，这五个基因之间未检测到异二聚体。最后，构建了过量表达上述五个基因的拟南芥品系，这些转基因品系显示出改变的初生根长度，耐盐性和育性。结论研究了所有玉米TCA循环基因的序列组成，重复模式，系统发生关系，顺式元件，表达模式和相互作用网络。五个玉米TCA基因在拟南芥中过表达，它们可以改变初级根长，耐盐和肥力。总之，我们的发现可能有助于揭示TCA基因在玉米中的分子功能。