EMS Mutagenesis in the Pea Aphid [i]Acyrthosiphon pisum[/i]
Résumé
In aphids, clonal individuals can show distinct morphological traits in response to environmental cues. Such phenotypic plasticity cannot be studied with classical genetic model organisms such as [i]Caenorhabditis elegans[/i] or [i]Drosophila melanogaster[/i]. The genetic basis of this biological process remain unknown, as mutations affecting this process are not available in aphids. Here, we describe a protocol to treat third stage larvae with an alkylating mutagen, ethyl methanesulfonate (EMS), to generate random mutations within the [i]Acyrthosiphon pisum[/i] genome. We found that even low concentrations of EMS were toxic for two genotypes of [i]A. pisum[/i]. Mutagenesis efficiency was nevertheless assessed by estimating the occurrence of mutational events on the X chromosome. Indeed, any lethal mutation on the X-chromosome would kill males which are haploid on the X so that we used the proportion of males as an estimation of mutagenesis efficacy. We could assess a putative mutation rate of 0.4 per X-chromosome at 10 mM of EMS. We then applied this protocol to perform a small scale mutagenesis on parthenogenetic individuals, which were screened for defects in their ability to produce sexual individuals in response to photoperiod shortening. We found one mutant line showing a reproducible altered photoperiodic response with a reduced production of males and the appearance of aberrant winged males (wing atrophy, alteration of legs morphology). This mutation appeared to be stable since it could be transmitted over several generations of parthenogenetic individuals. To our knowledge, this study represents the first example of an EMS-generated aphid mutant.
Domaines
Biologie végétale
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