A phased genome of the highly heterozygous 'Texas' almond uncovers patterns of allele-specific expression linked to heterozygous transposon insertions
The vast majority of traditional almond varieties are self-incompatible and the level of variability of the species is very high, resulting in a highly heterozygosity genome. Therefore, information on the different haplotypes is particularly relevant to understand the genetic basis of trait variability in this species. However, although reference genomes for several almond varieties exist, none of them is phased and has genome information at the haplotype level. Here we present a phased assembly of genome of the almond cv. Texas. Our analysis shows that the “Texas” genome has a high degree of heterozygosity, both as SNPs, short indels, and structural variants (SV) level. Many of the SVs are due to heterozygous Transposable Element (TE) insertions, and in many cases they also contain genic sequences. In addition to the direct consequences of this genic variability on the presence/absence of genes, our results show that variants located close to genes tend to be associated with allele-specific gene expression (ASE), which highlights the importance of heterozygous SVs in almond. Overall design: Flowers (pink stage) and immature fruits of Prunus dulcis cv Texas and Prunus persica cv Early Gold were collected. For RNA-seq analysis, we used three biological replicates per genotype.