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. 2021 Feb 6;33(5):1472–1491. doi: 10.1093/plcell/koab044

Figure 7.

Figure 7

Evolutionary and metabolic models of HCT function. A, Evolutionary model for the conservation of the HCT/CYP98 pair in embryophytes. Gray branches represent organismal evolution of species. Green and cyan branches represent HCT (this study) and CYP98 (Alber et al., 2019) gene evolutions, respectively. CYP98 encodes p-coumaroyl 3′hydroxylase (C3′H). B, Metabolic model of P. patens phenylpropanoid pathway. HCT plays a pivotal role in controlling the formation and deconjugation of shikimate esters, the evolutionarily conserved intermediates for phenolic ring functionalization by C3′H enzyme. Shikimate partly derives from the pentose phosphate pathway and is a precursor of l-phenylalanine, potentially establishing a regulatory control of photosynthetic carbon allocation to the phenylpropanoid pathway through two critical steps. The occurrence of a CSE/4CL alternative route toward caffeoyl-CoA in P. patens remains an open question. E4P, D-erythrose 4-phosphate; PEP, phosphoenolpyruvate.