Galvez-Valdivieso Gregorio, Delgado-Garcia Elena, Diaz-Baena Mercedes, Montaño Oscar, Quiles Francisco A, Pineda Manuel, Piedras Pedro
Departamento de Botánica, Ecología y Fisiología Vegetal. Plants Molecular Physiology and Biotechnology Group, Campus de Rabanales, Edif. Severo Ochoa, Universidad de Córdoba, 14071 Córdoba, Spain.
Plants (Basel). 2020 Feb 1;9(2):171. doi: 10.3390/plants9020171.
Nucleotides are molecules of great importance in plant physiology. In addition to being elementary units of the genetic material, nucleotides are involved in bio-energetic processes, play a role as cofactors, and are also components of secondary metabolites and the hormone cytokinin. The common bean () is a legume that transports the nitrogen fixed in nodules as ureides, compounds synthetized from purine nucleotides. The first step in this pathway is the removal of the 5'-phosphate group by a phosphatase. In this study, a gene that codes for a putative nucleotidase () has been identified in . The predicted peptide contains the conserved domains for haloacid dehalogenase-like hydrolase superfamily. The protein has been overexpressed in and the purified protein showed molybdate-resistant phosphatase activity with nucleoside monophosphates as substrates, confirming that the identified gene codes for a nucleotidase. The optimum pH for the activity was 7-7.5. The recombinant enzyme did not show special affinity for any particular nucleotide, although the behaviour with AMP was different from that with the other nucleotides. The activity was inhibited by adenosine, and a regulatory role for this nucleoside was proposed. The expression pattern of shows that it is ubiquitously expressed in all the tissues analysed, with higher expression in nodules of adult plants. The expression was maintained during leaf ontogeny, and it was induced during seedling development. Unlike PvNTD1, another NTD previously described in common bean, the high expression of was maintained during nodule development, and its possible role in this organ is discussed.
核苷酸是植物生理学中非常重要的分子。除了作为遗传物质的基本单位外，核苷酸还参与生物能量过程，作为辅助因子发挥作用，并且还是次生代谢产物和激素细胞分裂素的组成成分。菜豆（Phaseolus vulgaris）是一种豆科植物，它将根瘤中固定的氮以脲类的形式运输，脲类是由嘌呤核苷酸合成的化合物。该途径的第一步是由磷酸酶去除5'-磷酸基团。在本研究中，已在菜豆中鉴定出一个编码假定核苷酸酶（PvNTD2）的基因。预测的肽含有卤代酸脱卤酶样水解酶超家族的保守结构域。该蛋白已在大肠杆菌中过表达，纯化后的蛋白以核苷单磷酸为底物表现出耐钼酸盐的磷酸酶活性，证实所鉴定的基因编码一种核苷酸酶。该活性的最适pH为7 - 7.5。重组酶对任何特定核苷酸都没有表现出特殊亲和力，尽管其对AMP的行为与对其他核苷酸的行为不同。腺苷对该活性有抑制作用，并提出了该核苷的调节作用。PvNTD2的表达模式表明它在所有分析的组织中普遍表达，在成年植物的根瘤中表达较高。在叶片发育过程中表达保持稳定，在幼苗发育过程中被诱导。与菜豆中先前描述的另一种NTD（PvNTD1）不同，PvNTD2在根瘤发育过程中保持高表达，并讨论了其在该器官中的可能作用。
