The synthesis of macromolecules in the left colleterial gland of Periplaneta americana during the reproductive cycle.
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The synthesis of proteins and RNA in the left colleterial gland (LCG) of P. americana during the reproductive cycle are cyclic, highly dynamic processes. The patterns of protein synthesis and accumulation in the gland fluctuate very rapidly throughout the reproductive cycle. Three major peaks in levels of protein synthesis are detected during the cycle. Two of these, occurring in close succession, take place before the onset of ootheca synthesis, whereas the last peak occurs shortly before ootheca deposition and extends into the early phases of the new cycle. The patterns of translational activity and protein accumulation in the gland suggest that the LCG could be involved in the production of proteins for export as well as for ootheca synthesis. The pattern of total RNA synthesis in the LCG closely follows that of protein synthesis during the reproductive cycle. Three major peaks in total RNA synthesis are observed, each of which occurs eight hours before a peak in protein synthesis and corresponds to enhanced production of poly(A)-RNA. The major increases in poly(A)+ RNA synthesis in the LCG correlate precisely with the peaks in protein synthesis. The LCG is known to be functionally dependent upon juvenile hormone (JH). However, the transcriptional and translational responses of the gland to the presence of the hormone in vitro are not stereotyped but highly stage-specific. Short term in vitro JH III treatment primarily affects RNA synthesis in the LCG, but the transcriptional response of the gland to the presence of the hormone may be positive (RNA synthesis stimulated), negative (inhibition of RNA synthesis) or null, depending on the stage of the cycle. The stages of high transcriptional activity observed in the LCG during the reproductive cycle correlate precisely with the stages at which in vitro JH III treatment elicits a large positive response from the isolated gland. The immediate translational response of the gland to the presence of JH III in vitro is generally negative, except at the stages of high endogenous translational activity. However, it is not entirely clear whether or not JH III is solely responsible for the initial appearance of the endogenous increases in RNA and protein synthesis observed in the LCG during the reproductive cycle. It is apparent that JH III is not the only regulatory factor controlling LCG activities during the reproductive cycle. A major regulatory system controlling the secretory and possibly transcriptional activities of the LCG during the reproductive cycle has been uncovered. In vitro ecdysterone treatment, of glands isolated at stages far removed from ovulation and the onset of ootheca synthesis, depresses transcriptional activity in the LCG and induces the gland to spontaneously release its luminal content. The inhibitory effects of ecdysterone upon in vitro RNA synthesis are only slightly alleviated by JH III when both hormones are present in equal amounts while ecdysone-induced secretory activity is inhibited. The presence of ovarioles isolated at 64h (onset of in vivo LCG secretory activity) in the incubation medium gives rise to a very strong inhibition of RNA synthesis in the LCG while concurrently inducing secretory activity is inhibited.