Abstract Detail

Comparative Genomics/Transcriptomics

Buchheim, Mark [1], Alanagreh, Lo'ai [2].

Intragenomic variation of ribosomal genes and evidence of concerted evolution in the opportunistic pathogen Candida.

Varying levels of intragenomic variation (IGV) in the ribosomal array (ITS2) have been reported for a broad range of organisms. Our interest in the topic has focused on comparing IGV levels in reproductively diverse strains of algae and fungi. We recently obtained sexual, parasexual and asexual strains of Candida with the goal of comparing IGV in these organisms with data from sexual and asexual strains of green algae. We used our recent adaptation of the Illumina metagenomics protocol for deep-sequencing of ITS2 amplicons from all genomic extracts. Raw reads were filtered using the FASTQ toolkit. High quality reads were paired and merged using the CLC Genomics Workbench. Results from deep sequencing showed that all sexual and parasexual Candida isolates showed no ITS2 variation. In contrast, the asexual isolate, Candida tropicalis, exhibited four variants, with the major variant constituting 71% of all copies. These observations parallel comparisons of selected green algae. The level of ITS2 variation in isolates of Chlamydomonas reinhardtii, a sexual green alga, was generally lower (2-4 variants) than in the asexual lineages of Haematococcus pluvialis (3-6 variants). Moreover, the levels of IGV as assessed by p-distances were substantially lower in C. reinhardtii than in H. pluvialis and its allies. Collectively, these observations are consistent with the hypothesis that concerted evolution—through unequal crossing over in meiosis—plays an important role in maintaining ribosomal homogeneity. These observations also support the notion that parasexuality involves some form of mitotic recombination that contributes to ribosomal homogeneity. The data presented here indicate that a survey of IGV in a broad sampling of sexual, parasexual and asexual organisms is needed to provide a more robust test of the concerted evolution hypothesis.

1 - University Of Tulsa, The, Biological Science, 800 South Tucker Drive, Tulsa, OK, 74014, United States
2 - The Hashemite University, Medical Laboratory Sciences, P.O. Box 330127, Zarqa, 13133, Jordan

Keywords:
Candida
Chlamydomonas
Haematococcus
concerted evolution
parasexuality
intragenomic variation
ITS2.

Presentation Type: Poster
Session: P, Comparative Genomics and Transcriptomics
Location: Grand Ballroom - Exhibit Hall/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PGT013
Abstract ID:943
Candidate for Awards:None