Flavone synthases from Lonicera japonica and L. macranthoides reveal differential flavone accumulation

Abstract

Flavones are important secondary metabolites found in many plants. In Lonicera species, flavones contribute both physiological and pharmaceutical properties. However, flavone synthase (FNS), the key enzyme responsible for flavone biosynthesis, has not yet been characterized in Lonicera species. In this study, FNSII genes were identified from Lonicera japonica Thunb. and L. macranthoides Hand.-Mazz. In the presence of NADPH, the recombinant cytochrome P450 proteins encoded by LjFNSII-1.1, LjFNSII-2.1, and LmFNSII-1.1 converted eriodictyol, naringenin, and liquiritigenin to the corresponding flavones directly. The different catalytic properties between LjFNSII-2.1 and LjFNSII-1.1 were caused by a single amino acid substitution at position 242 (glutamic acid to lysine). A methionine at position 206 and a leucine at position 381 contributed considerably to the high catalytic activity of LjFNSII-1.1. In addition, LjFNSII-1.1&2.1 and LmFNSII-1.1 also biosynthesize flavones that were further modified by O-glycosylation in transgenic tobacco. The expression levels of the FNSII genes were consistent with flavone accumulation patterns in flower buds. Our findings suggested that the weak catalytic activity of LmFNSII-1.1 and the relatively low expression of LmFNSII-1.1 in flowers might be responsible for the low levels of flavone accumulation in flower buds of L. macranthoides.

Pseudospins and Topological Effects of Phonons in a Kekulé Lattice

“…2(b)]. This result agrees with previous data [21][22][23][44][45][46], verifying our physical interpretation. The pseudospin-polarized interface states are ideal phonon conduction channels for topological pseudospin transport.…”

“…Therefore, Dirac states at the K and K ′ couple with each other, resulting in exotic physics in the distorted graphene, like chiral symmetry breaking, charge fractionalization, soliton, etc [41][42][43]. Recently, Wu et al theoretically proposed the realization of QSH-like states in a Kekulé lattice for photons [44] and electrons [45,46]. The proposal was soon generalized for acoustic systems that were examined experimentally [21][22][23].…”

Higher-Order Topological Phase in a Honeycomb-Lattice Model with Anti-Kekulé Distortion

“…Recently, such a modulated structure has been revisited in the context of topological phases protected by crystalline symmetries. [12][13][14][15][16][17] Indeed, it has been found that the single-orbital tight-binding model hosts a topological crystalline insulator, accompanied by characteristic edge states 13,14) as a typical example of the bulk-edge correspondence. 18) Such an implementation of the topological nature is also applied to photonic crystals.…”

π -fluxes, semimetals, and flat bands in artificial materials

“…1, in which we assign intra-hexagon hopping t 0 = t+δ for black bonds and inter-hexagon hopping t 1 = t − δ for red bonds. This modulation gaps out Dirac cones of the original honeycomb lattice model through the coupling between the Dirac cones at the K and K' points in the Brillouin zone [29][30][31]. Importantly, the states near zero energy are described by a massive Dirac equation where the sign of the mass term can be flipped by changing the ratio between |t 0 | and |t 1 |, or the sign of δ.…”