Metamorphic changes in fat body proteins of the southwestern corn borer, Diatraea grandiosella

Abstract

Developmental changes in the fat body proteins of the southwestern corn borer, Diatraea grandiosella, were studied from the beginning of the fifth instar to the newly ecdysed pupal stage. The dry weight of the perivisceral fat body was found to increase markedly from a mean of 1·15 mg/insect at 10 days of age to 7·9 mg in the newly ecdysed pupa (16 days). This rise was partially attributed to the increase in fat body protein content which took place during the same period. The fat body protein content rose from about 0·25 mg/insect at 10 days to a maximum of about 1·7 mg/insect in the newly ecdysed pupa. The rate of protein biosynthesis during this period was estimated using leucine- 14C as a tracer. Results showed that 14-day-old larval fat body, unlike that of newly ecdysed pupae, had a high rate of protein biosynthesis. The chronology of synthesis and accumulation of the major proteins was determined by subjecting the soluble fat body proteins to disk electrophoresis. A changing electrophoretic pattern was detected between 10 and 15 days, which coincided with the period of active protein biosynthesis. Analyses of 15-day-old mature larval fat body revealed the presence of three major soluble proteins whose titre greatly increased after pupal ecdysis. The relationship between fat body and haemolymph proteins and the rôle of the major fat body proteins in adult differentiation are discussed.