Identification of Two Brassinosteroids from the Cambial Region of Scots Pine (Pinus silverstris) by Gas Chromatography-Mass Spectrometry, after Detection Using a Dwarf Rice Lamina Inclination Bioassay

A simple and improved dwarf rice ( Oryza sativa var Tan-ginbozu) lamina inclination bioassay for brassinosteroids (BRs) was developed based on a previously published method (K Takeno, RP Pharis [1982] Plant Cell Physiol 23: 1275-1281). The assay used 3-day-old intact seedlings, and detection of BR was made more sensitive by synergizing the response to BR with indole-3-acetic acid (IAA). The minimum detectable amount of BR was less than 0.1 nanogram/rice plant (brassinolide equivalents). Purification steps for isolation of BR from tissue scrapings taken from the cambial region of Scots pine ( Pinus silverstris ) harvested during the period of rapid wood production were guided by this assay. After column chromatography (silica gel and PrepPak C 18 ) and reversed phase C 18 high performance liquid chromatography, the biologically active fractions were analyzed by gas chromatography-mass spectrometry (GC-MS) and/or GC-MS-selected ion monitoring. Two BRs, castasterone (major) and brassinolide (minor) were identified. This is the first identification of BR from the cambial region of a conifer.