Beta-ketoacyl-coenzyme A reductase required for the elongation of fatty acids precursors of sphingolipids, triacylglycerols, cuticular waxes and suberin. Responsible for the first reduction step in very long-chain fatty acids (VLCFAs) synthesis. Decreased expression of KCR1 (RNAi) leads to plants with fused vegetative and reproductive organs, and abnormal trichome, epidermal cell and root morphology. Cannot be complemented by KCR2. a very-long-chain (3R)-3-hydroxyacyl-CoA + NADP(+) = a very-long-chain 3-oxoacyl-CoA + H(+) + NADPH Lipid metabolism; fatty acid biosynthesis. Part of the fatty acid elongase complex which contains a beta-ketoacyl-CoA synthase (KCS), a beta-ketoacyl-CoA reductase (KCR), a beta-hydroxyacyl-CoA dehydratase (HCD) and an enoyl-CoA reductase (ECR). Expressed in green siliques, flowers, inflorescence stems, leaves and roots. Expressed in embryos of different stages and young developing seedlings, but absent from mature seeds. Embryo lethal when homozygote. Belongs to the short-chain dehydrogenases/reductases (SDR) family. Truncated N-terminus.