Abstract:

The aposymbiotic  Nilaparvata lugens Stål was obtained by three day high temperature treatment (35℃) and then reared on chemically defined diets with one of 20 amino acids deleted. The relative growth rate and number of yeastlike symbiotes of aposymbiotic  N. lugens were studied. The results showed that tenessential amino acids were more important for the growth of aposymbiotic N. lugens than ten non essential ones, and the number of yeast like symbiotes increased in N. lugens, especially in aposymbiotic ones, which were reared on diets with one of essential amino acids deleted. The amino acid composition and activity of transamidase in aposymbiotic N. lugens reared on the complete diet D-97 were also tested. There was no change in protein composition in aposymbiotic N. lugens, but the total amount of free amino acids increased significantly and the ratio of essential amino acids decreased, with the molar percentage of essential amino acids such as histidine, isoleucine, leucine, lysine, methionine and phenylalanine decreased markedly. The results suggested a relative reduction of the essential amino acids be an important factor on  hindering protein synthesis. The activity of glutamine synthetase (GS) and alanine aminotransferase (ALT) increased obviously, while aspartate aminotransferase (AST) decreased distinctly. Combined with the result that glutamine increased remarkably, it was inferred that yeast like symbiotes may use glutamine as resource to synthesize essential amino acids.

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Key words: Nilaparvata lugens, yeast like symbiotes, amino acid, glutamate synthase, aminotransferase