Biology subjects

Paritosh, K.

Publications and source records attributed to Paritosh, K..

3 recordsLinked to original sources

bioRxiv2019

Comparative genomics of Alternaria species provides insights into the pathogenic lifestyle of Alternaria brassicae - a pathogen of the Brassicaceae family

Alternaria brassicae, a necrotrophic pathogen, causes Alternaria Leaf Spot, one of the economically important diseases of Brassica crops. Many other Alternaria spp. such as A. brassicicola and A. alternata are known to cause secondary infections in the A. brassicae-infected Brassicas. The genome architecture, pathogenicity factors, and determinants of host-specificity of A. brassicae are unknown. In this study, we annotated and characterised the recently announced genome assembly of A. brassicae and compared it with other Alternaria spp. to gain insights into its pathogenic lifestyle. Additionally, we sequenced the genomes of two A. alternata isolates that were co-infecting B. juncea. Genome alignments within the Alternaria spp. revealed high levels of synteny between most chromosomes with some intrachromosomal rearrangements. We show for the first time that the genome of A. brassicae, a large-spored Alternaria species, contains a dispensable chromosome. We identified 460 A. brassicae-specific genes, which included many secreted proteins and effectors. Furthermore, we have identified the gene clusters responsible for the production of Destruxin-B, a known pathogenicity factor of A. brassicae. The study provides a perspective into the unique and shared repertoire of genes within the Alternaria genus and identifies genes that could be contributing to the pathogenic lifestyle of A. brassicae.

genomics↗

bioRxiv2019

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

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.

genomics↗

bioRxiv2019

BjuWRR1, a CC-NB-LRR gene identified in Brassica juncea, confers resistance to white rust caused by Albugo candida

White rust caused by oomycete pathogen Albugo candida is a significant disease of crucifer crops including Brassica juncea (mustard), a major oilseed crop of the Indian subcontinent. Earlier a resistance-conferring locus named AcB1-A5.1 was mapped in an east European gene pool line of B. juncea - Donskaja-IV. This line was tested along with some other lines of B. juncea (AABB), B. rapa (AA) and B. nigra (BB) for resistance to six isolates of A. candida collected from different mustard growing regions of India. Donskaja-IV was found to be completely resistant to all the tested isolates. Sequencing of a BAC spanning the locus AcB1-A5.1 showed the presence of a single CC-NB-LRR protein encoding R gene. The genomic sequence of the putative R gene with its native promoter and terminator was used for the genetic transformation of a susceptible Indian gene pool line Varuna and was found to confer complete resistance to all the isolates. This is the first white rust resistance-conferring gene described from Brassica species and has been named BjuWRR1. Allelic variants of the gene in B. juncea germplasm and orthologues in the Brassicaceae genomes were studied to understand the evolutionary dynamics of the BjuWRR1 gene.\n\nHighlightBjuWRR1, a CNL type R gene, was identified from an east European gene pool line of Brassica juncea and validated for conferring resistance to white rust by genetic transformation.

plant biology↗