Active role of fatty acid amino acid conjugates in nitrogen metabolism in Spodoptera litura larvae.
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 (14)C-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 (15)NH(4)Cl 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.
Yoshinaga
Naoko
N
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
Aboshi
Takako
T
Abe
Hiroaki
H
Nishida
Ritsuo
R
Alborn
Hans T
HT
Tumlinson
James H
JH
Mori
Naoki
N
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D002851:Chromatography, High Pressure Liquid; D004032:Diet; D005227:Fatty Acids / Q000378:metabolism*; D005247:Feeding Behavior; D005973:Glutamine / Q000378:metabolism; D007814:Larva / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D009584:Nitrogen / Q000378:metabolism*; D018411:Spodoptera / Q000378:metabolism*
D000596:Amino Acids; D005227:Fatty Acids; D005973:Glutamine; D009584:Nitrogen