Transgenic alfalfa (Medicago sativa) with increased sucrose phosphate synthase activity shows enhanced growth when grown under N2-fixing conditions
Transgenic alfalfa (Medicago sativa) with increased sucrose phosphate synthase activity shows enhanced growth when grown under N2-fixing conditions
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DOI：
10.1007/s00425-015-2342-0
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发表时间：
2015-10-01
期刊：
影响因子：
4.3
通讯作者：
Sengupta-Gopalan, Champa
中科院分区：
文献类型：
--
作者：
Gebril, Sayed;Seger, Mark;Sengupta-Gopalan, Champa
当在固氮条件下生长时，SPS 在苜蓿中的过度表达伴随着提早开花、植物生长加快以及元素氮和蛋白质含量的增加。蔗糖磷酸合酶（SPS；EC 2.3.1.14）是植物中蔗糖合成的关键酶。使用转基因方法在不同植物中过度表达 SPS 的结果差异很大，但普遍的共识是，SPS 活性的增加与新库的产生和库强度的增加有关。在豆科植物中，根瘤是一个强大的碳汇，在这项研究中，我们的目标是了解增加豆科植物中的 SPS 活性将如何影响根瘤的数量和功能。在这里，我们用由组成型 CaMV35S 启动子驱动的玉米 SPS 基因转化了苜蓿（Medicago sativa，cv. Regen SY）。我们的结果表明，SPS 在苜蓿中的过度表达伴随着根瘤数量和质量的增加以及整个植物水平固氮酶活性的总体增加。结节表现出有助于氮同化的关键酶水平的增加，包括谷氨酰胺合成酶和天冬酰胺合成酶。此外，转化体的茎显示出较高水平的运输氨基酸Asx，表明根瘤中氮的输出增加。转化体的芽和根的生长显着增加，并且开花时间提前，从而导致产量增加。此外，转化体显示元素氮和蛋白质含量增加。总体结论是，增加的 SPS 活性改善了氮状态和植物性能，表明以蔗糖形式提供更多碳可以增强根瘤中氮的获取和同化。
Overexpression of SPS in alfalfa is accompanied by early flowering, increased plant growth and an increase in elemental N and protein content when grown under N (2) -fixing conditions.Sucrose phosphate synthase (SPS; EC 2.3.1.14) is the key enzyme in the synthesis of sucrose in plants. The outcome of overexpression of SPS in different plants using transgenic approaches has been quite varied, but the general consensus is that increased SPS activity is associated with the production of new sinks and increased sink strength. In legumes, the root nodule is a strong C sink and in this study our objective was to see how increasing SPS activity in a legume would affect nodule number and function. Here we have transformed alfalfa (Medicago sativa, cv. Regen SY), with a maize SPS gene driven by the constitutive CaMV35S promoter. Our results showed that overexpression of SPS in alfalfa, is accompanied by an increase in nodule number and mass and an overall increase in nitrogenase activity at the whole plant level. The nodules exhibited an increase in the level of key enzymes contributing to N assimilation including glutamine synthetase and asparagine synthetase. Moreover, the stems of the transformants showed higher level of the transport amino acids, Asx, indicating increased export of N from the nodules. The transformants exhibited a dramatic increase in growth both of the shoots and roots, and earlier flowering time, leading to increased yields. Moreover, the transformants showed an increase in elemental N and protein content. The overall conclusion is that increased SPS activity improves the N status and plant performance, suggesting that the availability of more C in the form of sucrose enhances N acquisition and assimilation in the nodules.