Metabolism in summer, winter and post winter diapausing pupae of Mamestra brassicae

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08660049
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 植物保護
• Research Institution: Yamagata University
• Principal Investigator: GOTO Michiyo Yamagata University, Agriculture Associate Professor, 農学部, 助教授 (10007081)
• Project Period (FY): 1996 – 1997
• Keywords: Mamestra brassicae / Summer diapause / Winter diapause / cryoprotectants / Trehalose / Glucose / Glycogen / Free amino acid

Research Abstract

The seasonal timing of diapause termination in pupae of Mamestra brassicae was determined by transferring overwintering pupae collected from the field at different seasons to an incubator at 26ﾟC under light off condition (OL-24D). When summer generation pupae were transferred to the incubator, the incubation time required for adult emergence was 44.8 days in july, 10.1 days in middle August and 1.9 days in late August. When winter generation pupae were transferred to the incubator, the required incubation time was 21.8 days in November, 16.6 days in December, 15.6 in January and 16.4 days in February. These results suggest that the summer diapause is terminated in summer and winter diapause is terminated before winter. The seasonal changes of carbohydrate and free amino acid content were investigated. Trehalose, glucose and inositol were detected in the haemolymph and body by gas-liquid chromatography. Trehalose was a dominant substance and its content increased with decreasing glycog en in spite of diapause termination in December. Twenty nine kinds of free amino acids were detected in the haemolymph, of these substances, Ala content in winter generation showed an increase from diapausing stage to postdiapausing stage. The relationship between temperature and carbohydrate or free amino acid content were investigated in summer diapausing, winter diapausing and post winter diapausing pupae. Pupae collected in July (summer diapausing stage), in November (winter diapausing stage) and in January (post winter diapausing stage) were incubated for 20 days at six different temperatures (-10 to 30ﾟC). Trehalose in both the summer and winter diapausing pupae were high at 0ﾟC,however, the trehalose content in post-winter diapausing pupae was high at -5ﾟC.Glycogen contents were almost inversely proportional to trehalose contents in summer diapausing pupae and in post-winter diapausing pupae, but glycogen content in winter diapausing pupae showed low level at -5ﾟC.Fifteen free amino acid contents changed significantly by the different acclimation temperatures, but the levels of Ser rose enormously at low temperature (-5ﾟC to -10ﾟC) in winter diapausing pupae. These results suggest that efficient trehalose synthesis occurs under the combination of low temperature and post-diapausing stage, so that cold hardiness in pupae may rise to a high level in winter.