We made quinoneless Bombardier beetles. That’s right. Weird and cool. We are practicing our mad-scientist cackling laughs now.
It’s very exciting news from my lab, or more correctly from the collaborative consisting of Wendy Moore’s Lab (U. of AZ), who developed the transcriptome data, provided beetles and help me conceptualize the study; Athula Attygalle’s lab (Stevens Tech. Un.) who did all the GC/MS analyses; Aman Gill (currently at SUNY, Stony Brook) who did the molecular genetics and bioinfomatics work; and me. I am the beetle whisperer doing the injections and dissections (usually what I’m whispering to the beetles is “hold the fuck still, this won’t hurt…much” Fig. 1).
In a nutshell this is what we did: Transcriptome data was acquired for Brachinus elongatus and explored for genes potentially related to the production of defensive secretions by scanning transcriptomes from secretory cells and non-secretory cell tissues, focusing on transcripts with higher relative abundance and expression in secretory cells. From those we selected target genes and used RNAi, i.e designed dsRNA to block the function of those genes. Beetles were forced to spray to exhaustion and then injected with the dsRNA solution. As they refilled their gland reservoirs the quinone genes were shut down and so they filled up with hydrocarbons, water and other constituents, but not quinones!
So we get a quinoneless phenotype (Fig. 2). A bombardier with all the pop and not so much bitter taste. (Okay I didn’t really taste them. Should I?). We submitted a preliminary proposal for funding to take this study to a much higher, comparative level. If funded (LOL) we will do this across exemplars of carabid beetles that produce different primary defensive compounds, like the Promecognathus in my last post; which produces methacrylic acid. We will tie the gene function to biosynthesis using labeled amino acid precursor injections and quantify effects on predation by subjecting altered phenotypes to predation studies.
Though the techniques still need refining, we see a ton of interesting questions about the function and evolution of allomone defenses that can be addressed using these methods and taxa. We plan to flesh out this preliminary effort into a proper paper-worthy study in the near future.
In the mean time I’ll be: