3.3 Genome synteny and Phylogeny analysis
To gain insights into an evolutionary perspective for M. dirhodum , a whole genome-based phylogenetic analysis was performed with eight other hemipteran insect species, including M. persicae ,D. noxia , A. pisum ,R. maidis , M. sacchari , N. lugens , B. tabaciand A. lucorum . D. melanogaster was used as the outgroup. A total of 209,881 genes to 22,945 orthogroups for the 10 species comparison were assigned (Fig. 2). A phylogenetic tree was constructed using the single-copy orthologous genes (Table S3). As a result,M. dirhodum and the five other Aphididae insects formed an Aphididae cluster, which showed that M. dirhodum is close toA. pisum and separated from M. sacchari and R. maidis . Three other Hemipteran insects, including B. tabaci ,N. lugens and A. lucorum, formed another cluster (Fig. 2).
Syntenic relationships between the M. dirhodum and A. pisum genomes were compared. The results reveal high levels of genome rearrangement between chromosomes of M. dirhodum and A. pisum , and a number of fission and fusion events were observed. Chr1 inM. dirhodum shares 81.9% of the syntenic blocks of chr X inA. pisum (Fig. 3). Considering the conservation of the X chromosome in Aphidini insects (Biello et al., 2021), we inferred that chr 1 might be the sex chromosome in M. dirhodum . In addition, chrA1 in A. pisum is mainly syntenic to chr2, chr4, chr5 and chr8 of M. dirhodum . ChrA2 in A. pisum is mainly syntenic to chr6, chr7 and chr9 of M. dirhodum . ChrA3 in A. pisum is mainly syntenic to chr3 in M. dirhodum . However, many fusion events covering small regions occurred in all chromosomes between these two insect species (Fig. 3).