Active role of fatty acid amino acid conjugates in nitrogen metabolism in Spodoptera litura larvae
Active role of fatty acid amino acid conjugates in nitrogen metabolism in Spodoptera litura larvae
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DOI：
10.1073/pnas.0809623105
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发表时间：
2008-11-18
影响因子：
11.1
通讯作者：
Mori, Naoki
中科院分区：
文献类型：
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作者：
Yoshinaga, Naoko;Aboshi, Takako;Mori, Naoki
自从1997年从夜蛾幼虫的反刍物中分离到第一个脂肪酸氨基酸偶联物（FAC） [volicitin: N-（17-羟基亚麻烯酰）- l -谷氨酰胺]以来，它们作为植物诱导反应的激发子的作用已经得到了很好的报道。然而，对FACs在昆虫体内的生物合成和生理作用的研究很少。通过c -14标记的谷氨酰胺、谷氨酸和亚麻酸对斜纹夜蛾幼虫的摄食研究，结合组织分析，我们发现中肠细胞中的谷氨酰胺是FACs生物合成的主要来源。此外，FACs中20%的谷氨酰胺片段是通过谷氨酰胺合成酶（GS）的酶促反应从谷氨酸和氨中获得的。为了确定FACs是否能提高GS产量，我们研究了斜纹夜蛾幼虫在人工饲料中(NH4Cl)-N-15和谷氨酸的氮同化效率。饲粮中添加亚麻酸后，氮同化效率从40%提高到60%。在管腔内，生物合成的fac被水解成脂肪酸和谷氨酰胺，再被组织和血淋巴吸收。这些结果有力地表明，鳞翅目幼虫体内含有谷氨酰胺的FACs在氮同化过程中起着积极的作用，肠道内含有谷氨酰胺的FACs可能是谷氨酰胺的一种储存形式，谷氨酰胺是氮代谢的关键化合物。
Since the first fatty acid amino acid conjugate (FAC) was isolated from regurgitant of Spodoptera exigua larvae in 1997 [volicitin: N-(17-hydroxylinolenoyl)-L-glutamine], their role as elicitors of induced responses in plants has been well documented. However, studies of the biosyntheses and the physiological role of FACs in the insect have been minimal. By using C-14-labeled glutamine, glutamic acid, and linolenic acid in feeding studies of Spodoptera litura larvae, combined with tissue analyses, we found glutamine in the midgut cells to be a major source for biosynthesis of FACs. Furthermore, 20% of the glutamine moiety of FACs was derived from glutamic acid and ammonia through enzymatic reaction of glutamine synthetase (GS). To determine whether FACs improve GS productivity, we studied nitrogen assimilation efficiency of S. litura larvae fed on artificial diets containing (NH4Cl)-N-15 and glutamic acid. When the diet was enriched with linolenic acid, the nitrogen assimilation efficiency improved from 40% to >60%. In the lumen, the biosynthesized FACs are hydrolyzed to fatty acids and glutamine, which are reabsorbed into tissues and hemolymph. These results strongly suggested that FACs play an active role in nitrogen assimilation in Lepidoptera larva and that glutamine containing FACs in the gut lumen may function as a form of storage of glutamine, a key compound of nitrogen metabolism.