Specific cell fate determination and differentiation (Xylem and phloem specification, root organization (patterning))
Abiotic stress signaling pathways (salt, drought, heat, cold, metal, vernalization etc.)
(b) the amount of the hormone (dosage or concentration)
(c) the sensitivity of that tissue to the hormone.
(d) the condition of the plant itself is critical: what is the condition of the plant? its age?
(a) ubiquitin-dependent protein degradation (negative regulator)
(b) tow component system (phospho-relay).
6. Manipulation of plant growth and development with knowledge from plant hormone signal transduction pathway. ex. Second green revolution.
Plant Hormone Signal transduction pathway
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Talk Outline
1. General introduction to cell signaling transduction pathways in plant.
2. Different plant hormones and their physiological function in plants.
3. Comparison between plant hormones and animal hormones action.
4. Ways or approaches in studying plant hormone
signaling transduction pathways.
5. Molecular mechanism of various plant hormone signal transduction pathways
3. Each hormone may result in multiple effects -- the particular effect depending on a number of factors:
(a) the presence of other hormones and the presence of activator molecules ( calcium, sugars)
Site of action x developmental stage x concentration of hormone? Crosstalk and specificity?
Chemical Structures of the Plant Hormones
plant hormones synthesis sites and their major functions
Analogy view of cell signaling transduction pathway
Input
(command)
Keyboard
Signal perception
Endogenous: phytohormone
Exogenous: environmental
cue
CPU (Central Processing
in cyclin F
Annals of Botany 99: 787-822 (2007)
Biological significance of ubiquitin/proteosome system (UPS) in plants
1. UPS was involved in different processes of plant life, including organ initiation and embryogenesis patterning, light signalling , circadian clock regulation ,hormone production, perception and signal transduction, and in plant defence.
E1; UBA, ubiquitin activating enzyme E2: UBC, ubiquitin conjugatingenzyme E3: ubiquitin protein ligase RBX: ring-box protein CUL: cullin CRL:cullin ring ligase HECT: homologous to E6-AP
2. Ethylene: histidine kinase Raf-like kinase CTR1 Mitogen activated protein kinase cascade
3. Cytokinin: phosphorelay (two-component system)
4. Gibberellin: G protein and DELLA protein hexosamine (NAcGlu)
Plant hormone signaling transduction (auxin, ethylene, cytokinin, gibberellin, abscisic acid, brasinosteroid, jasmonic acid etc.)
Definition of plant hormone
2007 (CHLH, GCR2)
Summary of molecular components involved
in plant hormone signaling transduction
1. Auxin: TIR1: F-box protein (Ubiquitin conjugated ligase) PIN1 (pin-formed 1) Aux/IAA repressor
COOH terminus RING: really interesting new gene
protein domain SCF: SKP1-Cullin-F-box SKP: S phase kinase associated protein F-box: SKP/ASK interaction motif
5. Abscisic acid: PP2C protein, SnRK protein kinase Farnesylation
6. Brasinosteroid: BRI1 (LRR-RLK)
An overview of the ubiquitination process in plants
Development regulatory pathway e. g. flowering (autonomous), lead, root, trichome formation
root apical meristem (RAM) shoot apical meristem (SAM) formation polarity and cell cytoskeleton rearrangement
2. The covalent attachment of ubiquitin to a substrate protein changes its fate. Notably, proteins typically tagged with a lysine48-linked polyubiquitin chain become substrates for degradation by the 26S proteasome.
Science, 2001
Dissect plant hormone signal transduction pathways by molecular genetic analysis
Chronological events and persons involved in identification of different hormone receptors
Main approaches used to study plant hormone perception,
signal transduction biosynthesis and responses
1. Molecular genetics approach
hormone biosynthetic mutants vs. hormone insensitive mutants
1. The word hormone is derived from the Greek verb meaning to excite.
2. hormones are organic substances synthesized in one tissue and transported out where their presence results in physiological responses ( not always true; may act at or close to synthesis site). They are required in minute amounts (10-6 to 10 -8M).