BAC-pool sequencing and analysis of large segments of A12 and D12 homoeologous chromosomes in upland cotton

PLoS One. 2013 Oct 8;8(10):e76757. doi: 10.1371/journal.pone.0076757. eCollection 2013.

Abstract

Although new and emerging next-generation sequencing (NGS) technologies have reduced sequencing costs significantly, much work remains to implement them for de novo sequencing of complex and highly repetitive genomes such as the tetraploid genome of Upland cotton (Gossypium hirsutum L.). Herein we report the results from implementing a novel, hybrid Sanger/454-based BAC-pool sequencing strategy using minimum tiling path (MTP) BACs from Ctg-3301 and Ctg-465, two large genomic segments in A12 and D12 homoeologous chromosomes (Ctg). To enable generation of longer contig sequences in assembly, we implemented a hybrid assembly method to process ~35x data from 454 technology and 2.8-3x data from Sanger method. Hybrid assemblies offered higher sequence coverage and better sequence assemblies. Homology studies revealed the presence of retrotransposon regions like Copia and Gypsy elements in these contigs and also helped in identifying new genomic SSRs. Unigenes were anchored to the sequences in Ctg-3301 and Ctg-465 to support the physical map. Gene density, gene structure and protein sequence information derived from protein prediction programs were used to obtain the functional annotation of these genes. Comparative analysis of both contigs with Arabidopsis genome exhibited synteny and microcollinearity with a conserved gene order in both genomes. This study provides insight about use of MTP-based BAC-pool sequencing approach for sequencing complex polyploid genomes with limited constraints in generating better sequence assemblies to build reference scaffold sequences. Combining the utilities of MTP-based BAC-pool sequencing with current longer and short read NGS technologies in multiplexed format would provide a new direction to cost-effectively and precisely sequence complex plant genomes.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chromosomes, Artificial, Bacterial / genetics*
  • Chromosomes, Plant / genetics*
  • Contig Mapping
  • DNA, Plant / chemistry
  • DNA, Plant / genetics*
  • Genome, Plant / genetics
  • Genomic Library
  • Gossypium / genetics*
  • Polyploidy
  • Reproducibility of Results
  • Retroelements / genetics
  • Sequence Analysis, DNA / methods*

Substances

  • DNA, Plant
  • Retroelements

Grants and funding

The authors would like to acknowledge the funding support for this work by USDA-CSREES grants ALAX-011-706 to RVK, ALAX-011-206 to GCS and NSF-PGRP grant 0703470 to RVK. The authors would like to acknowledge the support offered by Padmini Sripathi during data analysis and submissions. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.