NGS-based mapping of a morphogenetic mutant in the brown alga Ectocarpus siliculosus, by localization of a locus devoid of SNPs in the mutant segregative population.. Causal mutation locus mapping using NGS in Ectocarpus siliculosus

The mutant named therein “mut” was obtained from UV-B irradiation of E. siliculosus CCAP 1310/4 gametes. A segregative population was generated from the F1 individual by isolating one single haploid gametophyte from one single unilocular sporangium. A segregative parthenosporophyte population was generated from the cross mut x CCAP 1310/334, out of which [mut] individuals from independent meiotic events were isolated. Bulked genomic DNA of the [mut] segregative population was sequenced using the short read technique on a HiSeq2000 (Illumina) sequencer by the CNRS MGX platform (Montpellier, France). SNPs were inferred from the short reads using the DiscoSNP software. Then, each SNP was mapped onto the E. siliculosus genome. Analysis of the SNP density allowed to identify a ≈600kb region of strong SNP depletion, devoid of polymorphism because it is genetically linked to the [mut] phenotype.