Whole Transcriptome Changes Followed By Natural and Artificial Hybridization and Polyploidization in Peanut

Peanut (Arachis hypogaea L.) is a grain legume and also an oilseed crop widely cultivated in the world. Cultivated peanut is an allotetraploid (AABB type genome; 2n=4x=40), which contains A and B genome via hybridization and genome doubling. A. duranensis Krapov. & W.C.Gregory. and A. ipaensis Krapov. & W.C.Gregory are A- and B-genome diploid progenitors of cultivated peanut L.), respectively. Studies on plant polyploidization have reported that gene expression is altered by hybridization and polyploidy. In order to analyze the genomic changes that occur after allopolyploidization we explored genome-wide gene expression analysis of the synthetic allopolyploids: (A. ipaensis x A. duranensis)^4x, `resynthesized peanut`. We also used an interspecific diploid F₁ hybrid, and two natural allopolyploids. The F₁ hybrid is derived from the same parents and represents a genome merger without chromosome doubling. The synthetic allopolyploid derived from doubling this hybrid was included to observe the effect of polyploidization. A. monticola is considered as the immediate wild tetraploid ancestor of cultivated peanut and was therefore included in this study to detect signatures of domestication. First of all, novel expression and homoeolog silencing patterns were investigated. Furthermore, homoeolog expression bias and homoeolog expression level dominance were measured using orthologs between A- and B- genome ancestors. We also analyzed how homoeolog expression biases change during the course of evolutionary events. Novel patterns of gene expression and transposon activation were also observed.