A two-parter playing straight to my interests. Firstly, from last year, Industrial Melanism in the Peppered Moth Is Not Associated with Genetic Variation in Canonical Melanisation Gene Candidates from Ilik Saccheri and Arjen van't Hof. Work on an iconic evolutionary system, a possible role for a developmental switch between alternatives, in a Lepidopteran no less and from Liverpool as well! All the boxes ticked!
The authors initially look at all the usual suspects for melanic (darkened) phenotypes; the genes encoding tyrosine hydroxylase, ebony, tan, yellows etc. using targeted PCR (looking to selectively amplify and sequence genes of interest by hoping that the sequence is sufficiently similar to that from previously studied species) and from sequencing particular expressed genes (PCR and sequencing messenger RNAs by a technique called 3` RACE).
They find that NONE of the usual suspects appear to be involved (unless they have also been duplicated and the second copy has undergone unprecedented sequence change): none of the genes involved show association with either the normal or the darkened forms.
So what is going on? It appears that none of the identified candidates are involved. It could be that a copy of one of the candidates has escaped undetected (most likely in the large family of yellow genes), but this is quite unlikely. It seems that the melanisation in the iconic peppered moth is underlain by changes in a previously unsuspected gene - perhaps a regulatory gene, such as a transcription factor, which directs the patterning and the levels of expression of melanisation genes in the developing wing discs. The alternative forms (alleles) of such a gene would underpin a switch between two alternative developmental paths - one leading to a 'peppered' moth and the other to a darkened form better disguised against soot-darkened trees. Natural selection by predators acting on conspicuous moths would have added a new switch to the developmental 'programme' of these moths.
More on this tomorrow....
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