Huating Wang and Jyan-Chyun Jang
Department of Horticulture and Crop Science, The Ohio State University, e-mail: jang.40@osu.edu
Although brassinosteroids (BRs) are of known importance for plant development, the function of other plant steroid hormones is not known. We have identified a new Arabidopsis dwarf mutant, extra long lifespan1 (ell1), with both embryonic and postembryonic defects. ELL1 was cloned and found to encode a protein with sequence similarity to the human lamin B receptor/sterol reductase family and yeast C-14 sterol reductase. All the known BR-deficient mutants can be rescued by exogenous BRs, however, application of BRs did not rescue hypocotyl elongation in ell1 mutants. ell1 is allelic to an apical-basal patterning mutant fackel (fk) that also fails to develop a hypocotyl. It seems likely that abnormal sterol regulation of apical-basal axis formation is responsible for the defect of hypocotyl development, greatly increased lifespan, and shoot meristem hyperactivity of ell1 plants.