Genome and Transcriptome Sequencing of × Identified Sex-Associated Allele-Specific Expression of the Gene.

Transcriptome sequencing of leaves, catkin axes, and flowers from male and female trees of × and genome sequencing of the same plants were performed for the first time. The availability of both genome and transcriptome sequencing data enabled the identification of allele-specific expression. Such an analysis was performed for genes from the sex-determining region (SDR). × is an intersectional hybrid between species from sections () and (, , or × ); therefore, a significant number of heterozygous polymorphisms were identified in the SDR that allowed us to distinguish between alleles. In the SDR, both allelic variants of the (T-complex protein 1 subunit gamma), (Chloride channel protein CLC-c), and (DNA-methyltransferase 1) genes were expressed in females, while in males, two allelic variants were expressed for and but only one allelic variant prevailed for . Targeted sequencing of , , and regions on a representative set of trees confirmed the sex-associated allele-specific expression of the gene in generative and vegetative tissues of × . Our study brings new knowledge on sex-associated differences in species.