Conservation of function between mammalian and plant steroid 5alpha-reductases.
Arabidopsis det2 mutants are small dark-green dwarfs displaying pleiotropic defects in light-regulated development during multiple stages of the plant life cycle. The DET2 gene encodes a protein that shares approximately 40% sequence identity with mammalian steroid 5alpha-reductases and is implicated in the synthesis of a class of plant steroids, the brassinosteroids. Here we show that the DET2 protein, when expressed in human embryonic kidney 293 cells, catalyzes the 5alpha-reduction of several animal steroid substrates and has similar kinetic properties to the mammalian steroid 5alpha-reductase enzymes. Moreover, human steroid 5alpha-reductases expressed in det2 mutant plants can substitute for DET2 in brassinosteroid biosynthesis. These data indicate that DET2 is an ortholog of the mammalian steroid 5alpha-reductases and provide further evidence that brassinosteroids play an essential role in light-regulated plant development. The structural and functional conservation between DET2 and human steroid 5alpha-reductases raise interesting issues concerning the evolutionary origin of the steroid hormone signaling system.
Li
J
J
Plant Biology Laboratory, The Salk Institute, La Jolla, CA 92037, USA.
Biswas
M G
MG
Chao
A
A
Russell
D W
DW
Chory
J
J
D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000235:genetics*; D000818:Animals; D029681:Arabidopsis Proteins; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D008322:Mammals; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics*; D010944:Plants; D030821:Plants, Genetically Modified
D029681:Arabidopsis Proteins; C098907:DET2 protein, Arabidopsis; D018076:DNA, Complementary; D010940:Plant Proteins; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase