Progesterone is a mammalian hormone that has also been discovered in plants but its physiological function in plants is not explained. Experiments using inhibitors of progesterone synthesis and binding would be useful in studies on the significance of this compound in plants. Until now, trilostane and mifepristone have been used in medical sciences as progesterone biosynthesis and binding inhibitors, respectively. We tested these synthetic steroids for the first time in plants and found that they reduced the content of progesterone in wheat. The aim of further experiments was to answer whether the potential disturbances in the production/binding of progesterone, influence resistance to environmental stress (drought) and the development of wheat. Inhibitors and progesterone were applied to plants via roots in a concentration of 0.25-0.5mg/l water. Both inhibitors lowered the activity of CO2 binding enzyme (Rubisco) in wheat exposed to drought stress and trilostane additionally lowered the chlorophyll content. However, trilostane-treated plants were rescued by treatment with exogenous progesterone. The inhibitors also modulated the development of winter wheat, which indicated the significance of steroid regulators and their receptors in this process. In this study, in addition to progesterone and its inhibitors, brassinosteroid (24-epibrassinolide) and an inhibitor of biosynthesis of brassinosteroids were also applied. Mifepristone inhibited the generative development of wheat (like 24-epibrassinolide), while trilostane (like progesterone and an inhibitor of biosynthesis of brassinosteroids) stimulated the development. We propose a model of steroid-induced regulation of the development of winter wheat, where brassinosteroids act as inhibitors of generative development, while progesterone or other pregnane derivatives act as stimulators.

Department of Plant Physiology University of Agriculture in Krakow Podłużna 3 30 239 Krakow Poland

Laboratory of Growth Regulators Centre of the Region Haná for Biotechnological and Agricultural Research Institute of Experimental Botany ASCR and Palacký University Šlechtitelů 11 783 71 Olomouc Czech Republic

The Franciszek Górski Institute of Plant Physiology Polish Academy of Sciences Niezapominajek 21 30 239 Krakow Poland

References provided by Crossref.org

Pregnane derivatives in wheat (Triticum aestivum) and their potential role in generative development

Naturally Occurring Ecdysteroids in Triticum aestivum L. and Evaluation of Fenarimol as a Potential Inhibitor of Their Biosynthesis in Plants