Development of homozygous tetraploid potato lines and the dynamics of their expression, the enrichment of H3K27ac and enhanced resistance to cold-induced sweetening

Cultivated potato is highly heterozygous. Thus, in this study, we developed 2 homozygous autotetraploid lines and 1 homozygous diploid line in parallel from a homozygous diploid potato. We confirmed their ploidy levels using chloroplast counting and karyotyping. Oligo-FISH and genome re-sequencing validated that these potato lines are nearly homozygous. We investigated variations in phenotypes, transcription and histone modifications between 2 ploidies. Both autotetraploid lines produced larger but less tubers than the diploid line. Interestingly, each autotetraploid line displayed ploidy-related differential expression for various genes. We also discovered a genome-wide enrichment of H3K27ac in genic regions upon whole-genome doubling (WGD). However, such enrichment was not associated with the differential gene expression between 2 ploidies. The tetraploid lines may exhibit better resistance to cold-induced sweetening (CIS) than the diploid line in tubers, potentially regulated through the expression of CIS-related key genes, which seems to be associated with the levels of H3K4me3 in cold-stored tubers.