Effect of Cytochrome P450 on the Early Stage of Speciation
The selected and differentially expressed genes identified in the four
groups of A. viridiflora were enriched in cytochrome P450
(ko00199, CYP450) (Figure S7). CYP450 is the largest family of enzyme
proteins in plants and is involved in fatty acid metabolism, antioxidant
biosynthesis, plant defense, secondary metabolite biosynthesis, hormone
regulation and xenobiotic metabolism (Pandian, Sathishraj,
Djanaguiraman, Prasad, & Jugulam, 2020). These pathways play a key role
in the biosynthesis of secondary metabolites, antioxidants, and hormones
in higher plants. In our study, the 11 genes enriched in CYP450 belong
to eight subfamilies — CYP71, CYP76, CYP79, CYP81, CYP90, CYP98,
CYP707, and CYP711. For example, CYP98 is located at a key position in
the biosynthesis of phenylpropanoids, and the diversification of
phenylpropanoids provides a driving force for the development and
adaptation of terrestrial plants in new environments (A. Alber &
Ehlting, 2012; A. V. Alber et al., 2019). ABA 8’-hydroxylase protein is
encoded by the CYP707 gene and is the key step in ABA catabolism.
It can regulate the ABA level, thereby regulating the physiological
state of plants in response to environmental signals (Janda et al.,
2021; Zheng, Huang, Xian, Wang, & Liao, 2012). Other subfamilies play a
prominent role in the plant stress response (Irmisch, Zeltner, Handrick,
Gershenzon, & Köllner, 2015; Johnson et al., 2014; M. Wang et al.,
2020). Additionally, in response to environmental changes, the gene
expression levels of these subfamilies have also changed accordingly
(Baron, Schroeder, & Stasolla, 2012; Chan, 2012; Tao et al., 2017).
Therefore, the differentiation of the CYP450 superfamily may have driven
the speciation of A. viridiflora , and its diversification
provides a genetic basis to adapt to different environments. Because the
CYP450 superfamily is widely present in angiosperms, its important role
in the early speciation of angiosperms warrants further exploration.