Involved in vascular strand development. Catalyzes the stereospecific conversion of progesterone to 5-beta-pregnane-3,20-dione. Can use progesterone, testosterone, 21-acetyl cortexone, 2-cyclohexenone, but-1-en-3-one, ethyl acrylate, ethylmethacrylate, cortisone and canarigenone as substrates, lower activity with 3-methyl-2-cyclohexenone and 3,5,5-trimethyl-2-cyclohexenone as substrate, and no activity with canarigenin, canarigenin digitoxoside and pregnenolone. May be involved in the formation of 5-beta phytoecdysteroids. 5beta-cholestan-3-one + NADP(+) = cholest-4-en-3-one + H(+) + NADPH 4,5beta-dihydrocortisone + NADP(+) = cortisone + H(+) + NADPH kcat is 10.11 min(-1) with progesterone as substrate. kcat is 66.85 min(-1) with 2-cyclohexen-1-one as substrate. Optimum pH is 8.0. Optimum temperature is 45 degrees Celsius. Homodimer. Expressed in roots, stems, leaves, flowers, seeds and siliques. Expressed in the vascular bundles. Up-regulated by wounding. Not induced by drought, high salt, low temperature or herbicide treatment. Belongs to the short-chain dehydrogenases/reductases (SDR) family. Highly divergent.