A telomere-to-telomere reference genome provides genetic insight into the pentacyclic triterpenoid biosynthesis in Chaenomeles speciosa

Amplification of transposable elements 转座元件的扩增

Sequence mining disclosed that TEs were one main event in the expansion of the genome size of C. speciosa. To understand the roles of TEs in this expansion, the TE content of V. vinifera, R. chinensis, P. armeniaca, P. persica, P. communis, C. speciosa, and M. domestica were determined for comparison (Fig. 3A). Based on the types of TE, the genomes were classified into non-repeat, LTR-repeat, and non-LTR-repeat types. The results showed that the genomes of apple and C. speciosa had a similar LTR-repeat and non-LTR-repeat content that expanded during their evolution. In contrast, the LTR-repeat and non-LTR-repeat contents were contracted in the P. armeniaca and P. persica genomes. Further analysis of the insertion times of LTRs indicated that the proliferation of LTRs was ~0.05 and 0.08 MYA in P. armeniaca and C. speciosa, respectively and ~ 0.15 MYA in R. chinensis, pear, apple, and peach (Fig. 3B). This analysis also disclosed that the insertion time of LTRs was much earlier in grape than in the other six species.

序列挖掘揭示了转座元件（TEs）是C. speciosa基因组大小扩张的一个主要事件。为了理解TEs在这一扩张中的作用，研究人员对V. vinifera（葡萄）、R. chinensis、P. armeniaca（杏）、P. persica（桃）、P. communis（梨）、C. speciosa