Role of Arabidopsis sterol 4α-methyl oxidase2 family in embryo and postembryonic development.

Sterols play important roles in plant growth, including embryogenesis, cell expansion, vascular differentiation, male fertility, and endocytosis. Sterols become functional only after removal of the 2 methyl groups at C-4. There are 2 distinct sterol C-4-methyl oxidase (SMO) families in higher plants, SMO1 and SMO2, which contain 3 and 2 isoforms, respectively, involving in the removal of the first and second C4 methyl groups during sterols biosynthesis. In a recent study we showed that single smo2-1 and smo2-2 mutants displayed no significant phenotype, while smo2-1 smo2-2 double mutant was embryonic lethal. smo2-1/+ smo2-2 and smo2-1 smo2-2/+ mutants showed defect in abnormal embryo patterning and smo2-1 smo2-2/+ mutant displayed dwarf phenotype. In this mini-review, we summarize the functions and regulatory mechanisms of SMO2-1 and SMO2-2 in embryo and postembryonic development.