Analysis of Silk Gene Expression Profiles in Latrodectus hesperus for MaSp1&2

The black widow spider, Latrodectus hesperus, has the ability to produce a large variety of different silk types; these silks can be spun in different combinations so that the spider can utilize their distinct mechanical properties for specific functions in the web. Because different silks are secreted and stored in specific glands in the abdomen of the spider, we were interested in establishing which glands were actively transcribing specific silk genes. We previously isolated two silk genes, Major Ampullate Spidroin I (MaSp1) and Major Ampullate Spidroin 2 (MaSp2), which appear to code for proteins that compose dragline silk. To quantify the expression of these genes we dissected various silk glands from numerous black widow spiders to isolate mRNA from the glands. Since varying levels of mRNA generally correspond to varying levels of protein, we then quantified different mRNA levels in the glands by utilizing Real Time Quantitative Polymerase Chain Reaction (RT-QPCR). Using this method, we found high mRNA levels for both MaSp1 and MaSp2 in the major and minor ampullate glands, as well as high levels in the white tubuliform gland. This is significant in that previous publications indicate that silk gene expression is primarily gland specific. Given that expression was found outside of the major ampullate gland, our data indicate that silk gene expression may not be entirely gland specific.