Abstract
The genome size of the phytoseiid Metaseiulus (=Typhlodromus or Galendromus) occidentalis (Nesbitt) needs to be estimated before the whole nuclear genome can be sequenced. Two different procedures were used to estimate the genome size of M. occidentalis; (1) flow cytometry (Marescalchi et al. in Genome 33:789–793, 1990) and (2) quantitative real-time PCR (qRT-PCR) (Wilhelm et al. in Nucleic Acids Res 31:e56, 2003). Fluorescence intensity of propidium iodide-stained nuclei of M. occidentalis was measured by flow cytometry using females, males, and eggs. Only the eggs yielded peaks, which ranged in size from 35 to 160 Mb, with a tall peak of 140 Mb in 1-day-old eggs and 65 Mb in 2-day-old eggs, respectively. However, the peaks are broad and do not provide an accurate estimate. The qRT-PCR procedure required single-copy nuclear gene sequences from this phytoseiid. This was accomplished by designing degenerate primers, amplifying the Actin and EF1α sequences from M. occidentalis, and then designing M. occidentalis-specific primers that amplified a unique sequence. The standard qRT-PCR protocol was inefficient and amplification failed frequently, so we developed a high-fidelity qRT-PCR protocol, which utilizes a mix of two DNA polymerases (Taq and a proof-reading Tgo or ACCUZYME) to consistently amplify sequences. This allowed us to estimate the nuclear genome size of M. occidentalis as 88–90 ± 5 Mb. When compared to other arthropod genomes, this appears to be very small.
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This research was supported by the Davies, Fischer, and Eckes endowment to M. A. Hoy and the Institute of Food and Agricultural Sciences at the University of Florida.
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Jeyaprakash, A., Hoy, M.A. The nuclear genome of the phytoseiid Metaseiulus occidentalis (Acari: Phytoseiidae) is among the smallest known in arthropods. Exp Appl Acarol 47, 263–273 (2009). https://doi.org/10.1007/s10493-008-9227-x
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DOI: https://doi.org/10.1007/s10493-008-9227-x