A chromosome-scale assembly of allotetraploid Brassica juncea (AABB) elucidates comparative architecture of the A and B genomes

Kumar Paritosh, Satish Kumar Yadava, Priyansha Singh, Latika Bhayana, Arundhati Mukhopadhyay, Vibha Gupta, Naveen Chandra Bisht, Jianwei Zhang, David Kudrna, Dario Copetti, Rod A. Wing, Vijay Bhaskar Reddy Lachagari, Akshay Kumar Pradhan, Deepak Pental

Research output: Contribution to journalArticlepeer-review

Abstract

Brassica juncea (AABB; genome size ∼920 Mb), commonly referred to as mustard, is a natural allopolyploid of two diploid species – B. rapa (AA) and B. nigra (BB). We report a highly contiguous genome assembly of an oleiferous type of B. juncea variety Varuna, an archetypical Indian gene pool line of mustard, with ∼100x PacBio single-molecule real-time (SMRT) reads providing contigs with an N50 value of >5Mb. Assembled contigs were corrected and scaffolded with BioNano optical mapping. Three different linkage maps containing a large number of GBS markers were developed and used to anchor scaffolds/contigs to the 18 linkage groups of B. juncea. The resulting chromosome-scale assembly is a significant improvement over the previous draft assembly of B. juncea Tumida, a vegetable type of mustard. The assembled genome was characterized for transposons, centromeric repeats, gene content, and gene block associations. Both A and B genomes contain highly fragmented gene block arrangements. In comparison to the A genome, the B genome contains a significantly higher content of LTR/Gypsy retrotransposons, distinct centromeric repeats and a large number of B. nigra specific gene clusters that break the gene collinearity between the A and the B genomes. The genome assembly reported here will provide a fillip to the breeding work on oleiferous types of mustard that are grown extensively in the dry land areas of South Asia and elsewhere.

Original languageEnglish (US)
JournalUnknown Journal
DOIs
StatePublished - Jun 25 2019

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • Immunology and Microbiology(all)
  • Neuroscience(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)

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