Rice can absorb less than 40% of applied nitrogen fertilizer, whereas the unabsorbed nitrogen fertilizer may cause environmental problems, such as algal blooms in freshwater and increased production of nitrous oxide, a greenhouse gas which is 300 times more potent than carbon dioxide. Development of nitrogen use efficient (NUE) rice is essential for more environmentally friendly rice production. Recently, NUE rice has been developed by root-specific expression of alanine aminotransferase (AlaAT) gene from barley, a monocot plant. Therefore, we tested the efficacy of AlaAT gene from cucumber in transgenic rice, aiming to provide evidence for the conservation of AlaAT gene function in monocot and dicot. AlaAT gene from cucumber (CsAlaAT2) has been successfully cloned and constructed on pCAMBIA1300 plant expression vectors under the control of tissue-specific promoter OsAnt1. Agrobacterium tumefaciens-mediated transformation of Indonesian rice cv. Fatmawati using this construct produced 14 transgenic events. Pre-screening of T1 seedlings grown in the agar medium containing low nitrogen concentration identified selected events that were superior in the root dry weight. Southern hybridization confirmed the integration of T-DNA in the selected event genomes, each of them carried 1, 2, or 3 T-DNA insertions. Efficacy assay of three lead events in the greenhouse showed that in general transgenic events had increased biomass, tiller number, nitrogen content, and grain yield compared to WT. One event, i.e., FAM13, showed an increase in yield as much as 27.9% and higher plant biomass as much as 27.4% compared to WT under the low nitrogen condition. The lead events also showed higher absorption NUE, agronomical NUE, and grain NUE as compared to WT under the low nitrogen condition. The results of this study showed that root-specific expression of cucumber alanine aminotransferase2 gene improved nitrogen use efficiency in transgenic rice, which indicate the conservation of function of this gene in monocot and dicot.

中文翻译：

---

黄瓜丙氨酸转氨酶2基因的表达提高转基因水稻中氮的利用效率

水稻吸收的氮肥不到40％，而未吸收的氮肥可能引起环境问题，例如淡水中的藻华和氮氧化物的产生增加，一氧化氮的温室效应比二氧化碳高300倍。氮高效利用水稻的发展对于更环保的水稻生产至关重要。近来，通过从单子叶植物大麦中的谷氨酸丙氨酸氨基转移酶（AlaAT）基因的根特异性表达开发了NUE水稻。因此，我们测试了转基因水稻中黄瓜中AlaAT基因的功效，旨在为单子叶植物和双子叶植物中AlaAT基因功能的保守提供证据。在组织特异性启动子OsAnt1的控制下，已成功克隆并构建了pCAMBIA1300植物表达载体上的黄瓜AlaAT基因（CsAlaAT2）。根癌农杆菌介导的印度尼西亚水稻变异。Fatmawati使用此构建体产生了14个转基因事件。在低氮浓度的琼脂培养基中生长的T1幼苗的预筛选确定了在根干重方面优越的选定事件。Southern杂交证实了T-DNA在所选事件基因组中的整合，每个基因组均带有1、2或3个T-DNA插入片段。温室中三个主要事件的功效分析表明，与野生型相比，一般转基因事件增加了生物量，分till数，氮含量和谷物产量。一个事件，即FAM13，在低氮条件下，与野生型相比，大豆产量提高了27.9％，植物生物量提高了27.4％。与低氮条件下的WT相比，铅事件还显示出更高的吸收NUE，农艺NUE和谷物NUE。这项研究的结果表明，黄瓜丙氨酸氨基转移酶2基因的根特异性表达提高了转基因水稻的氮素利用效率，这表明该基因在单子叶植物和双子叶植物中的功能得以保留。