International research has significantly expanded our understanding of how brassinosteroids – one of the most important groups of plant hormones – function. The scientists have described how plants recognise these hormones. The results of the study were published in the prestigious scientific journal Nature Plants. The research involved scientists from the University of Geneva and the Laboratory of Growth Regulators, a joint facility of the Faculty of Science at Palacký University in Olomouc and the Institute of Experimental Botany of the Czech Academy of Sciences.
Brassinosteroids regulate a number of essential processes in plant life. They influence cell growth, the development of vascular tissues, reproduction, and plants' ability to respond to adverse conditions, such as drought and high or low temperatures. An international team led by researchers from the University of Geneva has now described in detail how individual brassinosteroids are recognised by cellular receptors and what determines their biological activity.
Plants recognise more hormones than previously thought
Using the model plant Arabidopsis thaliana, the researchers analysed the interactions between fifteen brassinosteroids and four receptors. It turned out that a greater number of these hormones bind effectively to the receptors than had previously been assumed. Previous research had focused primarily on brassinolide, which was considered the main biologically active member of this group.
The Olomouc team carried out the entire chemical and analytical part of the research. They prepared all the necessary synthetic and some natural brassinosteroid derivatives, whilst also analysing their natural concentrations in plants.
The chemical part of the research was carried out by scientists from Olomouc
“Without the preparation of a whole series of brassinosteroid derivatives, it would not have been possible to carry out this research on such a scale. At the same time, we found that, for example, castasterone or 28-homocastasterone occur in plants at significantly higher concentrations than brassinolide. Taken together with the results of the binding studies, this suggests that more brassinosteroids play a physiologically significant role than previously assumed,” said Miroslav Kvasnica from the Laboratory of Growth Regulators.
“We have clarified the chemical principles that determine the recognition of brassinosteroids by receptors. Although some compounds bind very strongly, they are unable to form a functional receptor complex and therefore do not trigger a biological response.” Jana Oklešťková
The study also showed that the biological activity of these hormones does not depend solely on how strongly they bind to the receptor. The correct orientation of the molecule within the receptor and its ability to form a functional complex with another protein, known as a co-receptor, are also crucial.
“We have elucidated the chemical principles that govern the recognition of brassinosteroids by receptors. Although some compounds bind very strongly, they cannot form a functional receptor complex and therefore do not elicit a biological response. ‘These findings may be important for further basic research into plant signalling,’ added Jana Oklešťková.
The results pave the way for further research
The new findings may facilitate the design of synthetic brassinosteroid analogues that are simpler and cheaper to produce than the currently known active compounds. However, the significance of the results lies primarily in expanding our fundamental understanding of how plant hormones function and in opening up new avenues for research into the regulation of plant growth and development. The authors point out that any potential practical application in agriculture will require further research.
In addition to the University of Geneva, the study involved scientists from the Laboratory of Growth Regulators, a joint research unit of the Institute of Experimental Botany of the Czech Academy of Sciences and the Faculty of Science at Palacký University in Olomouc. The Czech team consisted of Miroslav Kvasnica, Jana Oklešťková, Karoll Ferrer and Miroslav Strnad.