Brassinosteroid

These brassinosteroids were first explored during the 1970s when Mitchell et al. reported promotion in stem elongation and cell division by the treatment of organic extracts of rapeseed (Brassica napus) pollen.

The biosynthetic pathway was elucidated by Japanese researchers and later shown to be correct through the analysis of BR biosynthesis mutants in Arabidopsis thaliana, tomatoes, and peas.

One well-supported hypothesis is that all tissues produce BRs, since BR biosynthetic and signal transduction genes are expressed in a wide range of plant organs, and short distance activity of the hormones also supports this.

[6][7] Experiments have shown that long distance transport is possible and that the flow is from the base to the tips (acropetal), but it is not known if this movement is biologically relevant.

[citation needed] 24-Epibrassinolide (EBL), a brassinosteroid isolated from Aegle marmelos Correa (Rutaceae), was further evaluated for the antigenotoxicity against maleic hydrazide (MH)-induced genotoxicity in Allium cepa chromosomal aberration assay.

Based on extensive research BR has the ability to improve the quantity and quality of horticultural crops and protect plants against many stresses that can be present in the local environment.

"[19] There are some bioassays that can detect BRs in the plant such as the bean second internode elongation assay and the rice leaf lamina inclination test.

Brassinolide , the first brassinosteroid isolated and shown to have biological activity
Brassinosteroid signal cascade: in the absence of BR, BKI1 blocks BRI1 activity and BIN2 inhibits transcription factors. When BR is present, BKI1 dissociates from BRI1 and the BRI1:BAK1 complex is formed. This complex promotes the inactivation of BIN2 and transcription factors can then exert their effects.