Lanosterol synthase in dicotyledonous plants

Area of Science:

• Biochemistry
• Plant Biology
• Molecular Evolution

Background:

• Sterols are vital membrane components and hormone precursors in plants and animals.
• Plant sterols exhibit significant structural diversity and differ from animal sterols.
• Sterol biosynthesis pathways diverge early, with animals forming lanosterol and plants cycloartenol from 2,3-oxidosqualene.

Purpose of the Study:

• To investigate the origin of structural diversity in plant sterols.
• To explore alternative pathways in plant sterol biosynthesis.
• To identify genes involved in novel sterol backbone formation in plants.

Main Methods:

• Phylogenetic analysis of oxidosqualene cyclases.
• Heterologous expression of plant genes in yeast.
• Biochemical characterization of enzyme activity.

Main Results:

• Identified the Arabidopsis gene LAS1 (At3g45130) encoding a functional lanosterol synthase in plants.
• Demonstrated that plants can directly synthesize lanosterol from 2,3-oxidosqualene.
• Phylogenetic analysis revealed LAS1 belongs to a distinct branch of oxidosqualene cyclases, separate from cycloartenol synthases.
• Confirmed Panax PNZ on the same branch also functions as a lanosterol synthase.

Conclusions:

• Plants possess the capability to synthesize lanosterol, indicating a novel pathway for sterol biosynthesis.
• The existence of both lanosterol and cycloartenol synthase pathways may contribute to the extensive structural diversity observed in plant sterols.
• This discovery opens new avenues for understanding plant sterol metabolism and evolution.