PubMed · 10592760
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G Adam, J Schmidt, B Schneider. 1999. Brassinosteroids.. https://doi.org/10.1007/978-3-7091-6394-8_1
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A number of [26-2H(3)]brassinosteroids were prepared for biochemical studies. The parent, nondeuterated compounds were considered to be biosynthetic intermediates in brassinosteroid biosynthesis. Claisen rearrangement was used to construct the steroidal side chain. Deuterium was introduced by reducing the corresponding intermediates with lithium aluminium deuteride.
Plants express a variety of proteins at the cell surface responsible for the transduction of regulatory information into the cell via receptors. In the present study, an attempt has been made to identify the components of the brassinosteroids (BRs) signaling transduction cascades in transgenic rice (Oryza sativa) expressing the antisense strand of OsBRI1 transcript. A 60 kDa protein, immunologically characterized as mitogen-activated protein kinase (MAPK), showed reduced phosphorylation activity in the membrane fractions of the OsBRI1 antisense rice over control, demonstrating the inhibition in the perception of BRs by the BRI1 receptor, when compared with the exogenously applied brassinolide. The phosphorylation activity of the 50 kDa Ca(2+)-dependent protein kinase was however increased in the cytosolic fractions of OsBRI1 antisense over control. The data obtained suggest that MAPK and Ca(2+)-dependent protein kinase in rice are discrete but parallel signaling cascades and might involve receptors other than BRI1 in response to BR stimulus.
Ten novel compounds, each consisting of two subunits and a linker, were designed with the aid of molecular modeling to resemble the natural steroidal phytohormone brassinolide. The mimetics were synthesized and subjected to the rice leaf lamina inclination bioassay to test for brassinosteroid activity. Most of the mimetics displayed very weak or no bioactivity, but two were strongly active when coapplied with the auxin indole-3-acetic acid (IAA), which synergizes the activity of brassinosteroids. Thus, 1-(4,6 alpha,7 alpha-trihydroxy-5,6,7,8-tetrahydronaphthyl)-2-(6 alpha',7 alpha'-dihydroxy-5',6',7',8'-tetrahydronaphthyl)ethyne (4) and (E)-1,2-bis[trans-(4a alpha,8a beta)-4-oxo-6 alpha,7 alpha-dihydroxy-4a,5,6,7,8,8a-hexahydro-(3H)-naphthyl]ethylene (11) showed exceptional activity at doses as low as 0.01 ng and 0.001 ng/plant, respectively. These compounds are the first biologically active nonsteroidal brassinolide mimetics.