Why Do Plants Convert Sitosterol to Stigmasterol?

Siddique I Aboobucker,Walter P Suza

doi:10.3389/fpls.2019.00354

Abstract

A direct role for cholesterol signaling in mammals is clearly established; yet, the direct role in signaling for a plant sterol or sterol precursor is unclear. Fluctuations in sitosterol and stigmasterol levels during development and stress conditions suggest their involvement in signaling activities essential for plant development and stress compensation. Stigmasterol may be involved in gravitropism and tolerance to abiotic stress. The isolation of stigmasterol biosynthesis mutants offers a promising tool to test the function of sterol end products in signaling responses to developmental and environmental cues.

Highlights

Unlike mammals and fungi, plants produce mixtures of sterols, including sitosterol, stigmasterol, campesterol, and cholesterol (Figure 1)
Campesterol is the precursor of BR (Fujioka and Yokota, 2003), and the crucial role of BR in plant growth and development is well established (Fujioka et al, 1997; Choe et al, 1998, 1999; Noguchi et al, 1999; Nomura et al, 1999; Clouse, 2002), while sitosterol is implicated in cellulose synthesis (Peng et al, 2002; Schrick et al, 2012)
It is intriguing that blocking BR biosynthesis affects Sterol C-22 desaturase (CYP710A) gene expression (Supplementary Figure S1), suggesting a role for BR in regulating stigmasterol metabolism

Summary

Introduction

Plants produce mixtures of sterols, including sitosterol, stigmasterol, campesterol, and cholesterol (Figure 1). The interaction of sterols with phospholipids helps plant cells to maintain plasma membrane fluidity and permeability during stress conditions (Grunwald, 1971; Hartmann, 1998). Functional characterization of genes controlling stigmasterol biosynthesis might help increase our understanding of the direct role of this sterol in plant development and stress responses.

Results

Conclusion