Li J, Biswas M G, Chao A, Russell D W, Chory J
Plant Biology Laboratory, The Salk Institute, La Jolla, CA 92037, USA.
Proc Natl Acad Sci U S A. 1997 Apr 15;94(8):3554-9. doi: 10.1073/pnas.94.8.3554.
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.
拟南芥det2突变体是矮小的深绿色矮化植株，在植物生命周期的多个阶段的光调节发育中表现出多效性缺陷。DET2基因编码一种与哺乳动物类固醇5α-还原酶具有约40%序列同一性的蛋白质，并且参与一类植物类固醇即油菜素类固醇的合成。我们在此表明，当在人胚肾293细胞中表达时，DET2蛋白催化几种动物类固醇底物的5α-还原，并且具有与哺乳动物类固醇5α-还原酶相似的动力学性质。此外，在det2突变体植物中表达的人类固醇5α-还原酶可以在油菜素类固醇生物合成中替代DET2。这些数据表明DET2是哺乳动物类固醇5α-还原酶的直系同源物，并进一步证明油菜素类固醇在光调节的植物发育中起重要作用。DET2与人类固醇5α-还原酶之间的结构和功能保守性引发了有关类固醇激素信号系统进化起源的有趣问题。
