Discussion
Comparative genomics of
Saxifragales
Although seven species from four families of Saxifragales have published
whole-genome sequence assemblies (Fu et al., 2017; Yang et al.,
2017 ; Wai et al., 2019 ; Lv et al., 2020; Zhu et al.,
2020; Korgaonkar et al., 2021 ), only those of Paeonia
ostii and Cercidiphyllum japonicum were assembled at the
chromosomal level. Here, we successfully assembled the genome ofTiarella polyphylla , which is the first chromosome-level
sequencing, assembly, and annotation of the genome of Saxifragaceae. The
final size is 412.2 Mb, similar to the estimated genome size (393.29 Mb)
based on k-mer analysis. It is much smaller than estimates reported in
other genera of Saxifragaceae tribe Heuchereae (e.g., Mitella
diphylla , 1C = 0.57 pg; Bai et al., 2012 ; Heuchera
cylindrica, 1C = 0.48–0.52 pg; Godsoe et al., 2013 ). Our
results demonstrated that T. polyphylla , C. japonicum andHamamelis virginiana had no additional genome duplication after
the ancestral gamma hexaploidization event shared with all core
eudicots. These three genera span Saxifragales, demonstrating that there
is no ancestral genome-wide duplication characteristic of the entire
order. More details on comparative genomics and whole-genome duplication
are available in Discussion S1.