Metabolome analysis using multiple data mining approaches suggests luteolin biosynthesis in Physcomitrella patens

Area of Science:

• Plant biochemistry
• Moss metabolomics
• UV protection mechanisms

Background:

• The model land plant *Physcomitrella patens* is known to synthesize flavonoids.
• Flavonoids may play a role in protecting plants from ultraviolet-B (UVB) radiation damage.
• Understanding the flavonoid profile of *P. patens* can provide insights into plant stress responses.

Purpose of the Study:

• To investigate the flavonoid profile of the moss *Physcomitrella patens*.
• To identify specific flavonoids synthesized by *P. patens* and their potential roles.
• To explore the presence of enzymes involved in flavonoid biosynthesis, such as flavone synthase.

Main Methods:

• Metabolome analysis using liquid chromatography coupled with Ion trap/Orbitrap mass spectrometry (LC-MS).
• Analysis of 80% methanol extracts to detect and identify compounds.
• Utilized stable isotope labeling (¹³C, ¹⁵N, ¹⁸O, ³⁴S) for elemental composition confirmation.
• Compared MS/MS spectra with authentic standards for compound identification.

Main Results:

• Detected 661 valid peaks from *P. patens* extracts.
• Annotated 47 peaks as secondary metabolites, with 13 identified as potential flavonoid derivatives.
• Identified a peak corresponding to luteolin (C₁₅H₁₀O₆), a flavone, which was unexpected given the absence of known flavone synthase in *P. patens*.
• Confirmed the elemental composition and identified the compound as luteolin or related flavone isomers through spectral comparison.

Conclusions:

• This study reports the first evidence of luteolin or related flavone synthesis in *Physcomitrella patens*.
• The findings suggest the potential existence of a previously unknown enzyme with flavone synthase activity in this moss.
• The identified flavonoids may contribute to the plant's protection against UVB radiation.