The AKR4C family of AKR includes aldose reductase (ALR) from Hordeum vulgare (AKR4C1), Bromus inermis (AKR4C2), Avena fatua (AKR4C3), and Xerophyta viscosa (AKR4C4), two aldose reductases, DpAR1 (AKR4C5) and DpAR2(AKR4C6), from Digitalis purpurea, aldehyde reductase from Zea mays (AKR4C7), four aldo-keto reductases from Arabidopsis thaliana (AKR4C8-11), and another three aldo-keto reductases from Aloe arborescens (AKR4C12) and Oryza sativa (AKR4C14/15). ALR (EC 1.1.1.21), also called AR, aldehyde reductase, or polyol dehydrogenase (NADP(+)), is a cytosolic NADPH-dependent oxidoreductase that catalyzes the reduction of a variety of aldehydes and carbonyls, including monosaccharides. Both DpAR1 and DpAR2 reduce the ketone group of steroid structures. They may be involved in plant steroid metabolism in general and in cardenolide biosynthesis in particular. Plant aldo-keto reductases of the AKR4C subfamily play key roles during stress and are attractive targets for developing stress-tolerant crops.