Our studies have shown that the production of fibroin by the large ampullate glands of the spider Nephila clavipes consists of a series of well-orchestrated events which we have been able to detect through time-course studies. These have revealed four transient waves of molecular syntheses elicited by the mechanical stimulation of the glands, reproducible in both timing and relative amplitudes. A dramatic wave of fibroin synthesis peaks after 90 minutes of incubation of the glands. The latter is preceded by 60 minutes by the generation of the template. Intercalated between these two activities, at 45 minutes after stimulation, is a wave which enriches the glands with specific tRNAs cognate to fibroin´s predominant aminoacids: alanine, glycine and proline. The earliest of the waves at 15 minutes after stimulation, enriches the glands with small RNAs involved in template processing. The temporal and tissue-specific expressions of this system have led us to seek answers at the level of regulated expressions of the corresponding genes. Our search, thus far, has revealed a cluster of four alanine tRNA genes, one of which contains a distal upstream regulatory sequence, while two others contain proximal upstream regulatory sequences with AT-rich regulatory regions. We have also isolated and sequenced a 5S rRNA gene with an impressive level of homology (99.7%) with a corresponding 5S rRNA silkworm gene.
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