SPIDERS : THAT THIN STRAND AND ITS INTEGRATION WITH CRYSTALS : THE NEXT CONSTRUCTION MATERIAL : INTEGRATED LOGIC WEBS

CONTEMPORARY RELEVANCE OF SPIDROINS' 240-MILLION YEAR EVOLUTIONARY TIMELINE & THE WATER BEARS (TARDIGRADES)
AUG 17TH     SINCE TIME BEGAN : salus populi suprema est lex - the right of the people is the supreme law : IN TRUTH WE TRUST     2019.A.D.E.
Although all spiders make silk, perhaps the greatest complexity of silk production is displayed by araneoid orb-weavers, which possess seven distinct gland types that manufacture different silks with diverse functional applications. Molecular characterizations of araneoid silks has established that six of these glands (major ampullate, minor ampullate, flagelliform, aciniform, tubuliform and pyriform glands) each express unique combinations of spidroin paralogs [9, 19, 29, 59–61]. These paralogs encode proteins with varying proportions of structural motifs that underlie the signature mechanical properties of each fiber type. Outside of araneoids, there is tremendous variation in the number and types of silk glands, as well as the set of spidroin paralogs found across species. The evolution of this striking diversity can be investigated by jointly considering: 1) the phylogenetic relationships of spiders; 2) the distribution of silk glands among these lineages; and 3) the relationships of spidroins expressed by these glands and their sequence features.
2.  The presence of a similar, non-repetitive N-terminal domain in spidroin proteins across divergent spider lineages supports its participation in a general mechanism of spider silk production. Sequence conservation of these N-termini makes them an unequalled resource for reconstructing spidroin phylogeny. The improved understanding of spidroin relationships we provide using both N- and C-terminal domains shows that there is considerable evolutionary flexibility throughout the spider silk system, from the level of gene sequence motif to paralog number and silk gland expression pattern. This dynamic, labile nature of silk evolution is in stark contrast to the incredible homogeneity of repeats within some spidroins (e.g., 100% identity in consecutive 1026 bp repeats; [7]) and the consistently high-performing mechanical properties of silk fibers (e.g., dragline silks, [2]). Given the elevated rate of sequence rearrangement and turnover in the repetitive region, the spidroin N- and C-terminal domains are not only important for the biochemistry of silk fiber production, but also serve as signposts for retracing the history of the ancient and functionally diverse spider silks.


AUG 17TH     SINCE TIME BEGAN : salus populi suprema est lex - the right of the people is the supreme law : IN TRUTH WE TRUST     2019.A.D.E.
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