Abstract
A cDNA library from a pool of all the seven silk glands from a tropical spider species was constructed. More than 1000 expressed sequence tag (EST) clones were created. Almost 65% of the EST clones were identified and around 50% were annotated. The cellular and functional distribution of the EST clones indicated high protein synthesis activity in spider silk glands. Novel clones with repetitive amino acid sequences, which is one of the most important characteristics of spider silk genes, were isolated. One of these clones, namely TuSp2 in current research, contains two almost identical fragments with one short C-terminal domain. Reverse transcription (RT) PCR and expression analysis showed that it is expressed in the tubuliform gland and involved in eggcase silk formation. Furthermore, its single repetitive domain can be induced to form various types of materials, including macroscopic fibers, transparent film and translucent hydrogel. This study implies promising potentials for future identification of novel spidroins and development of new spidroin-based biomaterials.
Highlights
Spider silks have been renowned for their extraordinary mechanical properties
In addition to the major component of TuSp1, ADF-2 and ECP-1,2 were isolated from the tubuliform gland or egg case[5,12,13], which may be involved in the silk formation and/or conformation transition of the silk fiber assembly
Besides the attempt of identifying novel spider silk cDNA/genes, many efforts have been put on the spinning process, through which the soluble highly concentrated fibroin dope is converted to insoluble fibers[23,24,25,26,27]
Summary
Overview of EST clones in spider silk glands. A cDNA library from the 7 types of silk glands of 5 adult female N.a. was constructed. Fasta analysis showed that 698 of the 1076 clones had statistically significant similarity (Poisson P value ≤ 10−5, sequence overlap > 150 bp) to the available sequences in the public DNA database. This high identification rate may be mainly due to the pre-selection of the insert size, leading to sequencing only the coding region, which is more conservative than the 3′ UTR (un-translated region). Distribution of the identified clones in spider silk glands cDNA library. The cellular distribution of the genes expressed in one tissue represents roughly the energy distribution of this source tissue It provides us a profile of the energy flow and the molecular events involved in it.
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