Analysis of the arabidopsis dry2/sqe1-5 mutant suggests a role for sterols in signaling.

Sterols play multi-faceted roles in all eukaryotes. In plants, there are mounting evidences pointing to sterols, other than BRs, can act as signaling molecules. The Arabidopsis dry2/sqe1-5 mutant has multiple developmental defects caused by a point mutation in the SQE1 gene that generates a hypomorphic allele. SQE1 encodes a squalene epoxidase, which converts squalene into 2,3-oxidosqualene the precursor of plant sterols. Genetic, molecular and biochemical analyses suggest that dry2/sqe1-5 defective phenotypes cannot be simply explained by a depletion of bulk sterols but rather by altered ROS. It remains to be elucidated whether the altered ROS production of the mutant is caused by membrane composition, which in turn affect the lipid rafts composition and/or an altered signaling.