The first isolated brassinosteroid, it was discovered when it was shown that pollen from rapeseed (Brassica napus) could promote stem elongation and cell division.

[2] The production of brassinolide begins with a closely related sterol called campesterol, which is found in the cell membrane.

If the plant cannot perform C6 oxidation, it results in the "Dwarf phenotype," characterized by severe growth deficits.

[3] Finally, in Arabidopsis, the Baeyer-Villiger lactonization process occurs through the action of the two homologous enzymes CYP85A1 and CYP85A2, leading to the formation of brassinolide.

[5] Brassinosteroids, particularly the potent brassinolide, play a crucial role in controlling various plant processes such as germination, aging, and the ability to withstand environmental and biological stresses.

[6] Because of this, researchers from around the world have extensively studied model organisms like Catharanthus roseus and Arabidopsis since they were first isolated in 1979.

This interaction results in both proteins being chemically modified by the addition of phosphate groups in a process called phosphorylation.

This, in turn, sets off a chain reaction within the cell, activating some proteins and inhibiting others, including various kinases, phosphatases, and transcription factors.

As a result, protein phosphotase 2A (PP2A) can remove phosphate groups from two transcription factors, brassinazole-resistant-1 (BZR1) and BRI1-EMS-suppressor-1 (BES1), allowing them to accumulate within the cell's nucleus.

[6] The two transcription factors BES1 and BZR1 regulate a large number of genes involved in the synthesis of hormones, growth processes and stress response.

The enzyme CYP85A2 catalyzes the final biosynthesis step namely the Baeyer-Villiger lactonization of castasterone to brassinolide.