chapter 24 brassinosteroids novel growth-promoting substances in pollen 1970 mitchel et al the...
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Chapter 24 Brassinosteroids
novel growth-promoting substances in pollen
1970 Mitchel et al the pollen of rape plant (Brassica napus L.)
in the organic solvent fraction
physiological tests:
cell elongation, division, bending, swelling,
splitting of the second internode,
also increased total biomass and seed yield
1979 Grove et al 227 kg of bee-collected rape pollen
4 mg bioactive brassin compound,
named brassinolide
X-ray analysis: a polyhydroxylated steroid,
a steroidal lactone
1982 Yokota et al
chestnut galls purified castasterone, the precursor of brassinolide
1992 Abe and Yokota
the broadleaf evergreen tree Dystillium racemosum, a mixture of
biologically active brassinolide-like substance
1998 Clouse and Sasse
involved shoot growth, root growth, vascular differentiation,
fertility, and seed germination
Brassinosteroids have been identified in
27 families of seed plants, one pteridophyte, one bryophyte,
and one green alga
ubiquitous plant hormone
Two main bioassays of brassinosteroid
1. Bean second-internode bioassay
For several days
Stem thickening, bending, and splitting
Two main bioassays of brassinosteroid
2. The rice lamina inclination
amounts of [BS]
Biological active brassinosteroids brassinolide (BLs), side chain structure
Ring A C-2 and C-3
Cis-vicinal glycol function
Ring B
7-membrane lactone
24-epiBL: often used
28-homoBL
form
Brassinosteroids biosynthesis pathways
DET2 encode
5α-reductase
CPD encodes
Cyto P450 monooxygenase
Why?
(CL)
(CT)
(TE)
Brz
(CS)
(BL)
Light grown
det 2 mutant wild
Dark grown
det 2 wild
BRs act locally near their sites of synthesis
Reciprocal grafting
wild root
Endogenous BRs do not seem to undergo root-to-shoot (a long-distance) translocation
wild shoot
BRs: effects on growth and development
fiber development in cotton
development of lateral roots
maintenance of apical dominance
vascular differentiation
male sterility (pollen tube growth)
plant defense (resistance to infection)
seed germination
leaf senescence
Small- scale studies and large-scale trials using BRs
are bound to emerge,
is most beneficial to growth under stress conditions