Download presentation
Presentation is loading. Please wait.
1
Growth regulators Auxins Cytokinins Gibberellins Abscisic Acid Ethylene Brassinoteroids Jasmonic Acid Salicylic Acid Strigolactones Nitric Oxide Sugars
2
Brassinosteroids First identified in pollen from Brassicas (= brassins) Stimulate both elongation and cell division At low [] induce elongation At high [] induce division Assayed with bean stems or rice lamina
3
Brassinosteroids First identified in pollen from Brassicas (= brassins) Stimulate both elongation and cell division At low [] induce elongation At high [] induce division Assayed with bean stems or rice lamina Purified 4 mg from 227 kg of bee-collected pollen & determined structure by X-ray crystallography
4
Brassinosteroids Validated by mutants BR synthesis mutants are dwarf & defective rescued by BR BR-insensitive mutants are dwarf & defective don’t respond to BR
5
Brassinosteroids & other growth regulators
These gene products create BR responses Note overlap with Auxin! - interaction with ABA, eg in seed germination - interaction with ethylene & IAA transport in apical hook Promote skotomorphogenesis: BR mutants have COP phenotype. - interaction with jasmonate I in inhibition of root growth
6
Strigolactones Growth regulators derived from carotenoids Released from roots to attract endomycorrhizae trigger germination of parasitic plants, e.g. witchweed (Striga asiatica)
7
Strigolactones Growth regulators derived from carotenoids Interact with auxin to inhibit shoot branching Synthesized in response to P or N starvation increase lateral roots and root hairs & attract symbionts Trigger degradation of proteins that stimulate branching by an E3 ligase
8
Strigolactones Growth regulators derived from carotenoids Trigger degradation of proteins that stimulate branching by an E3 ligase Trigger degradation of SMAX1 via MAX2 E3 receptor Allows seed germination, seedling growth & development Link with karrikin signaling
9
Karrikins Growth regulators derived from carbohydrates by burning Stimulate germination of dormant seeds waiting for fire Trigger degradation of SMAX1 via MAX2 E3 receptor Allows seed germination, seedling growth & development
10
Salicylic Acid Affects plant growth and development Photosynthesis Transpiration ion uptake and transport
11
Salicylic Acid Best characterised role is in systemic acquired resistance Whole plant response following exposure to a pathogen Necrotic lesion releases phloem-mobile signal inducing Sa in target (could be methyl-SA or a lipid) SA induces expression of defense proteins via NPR1
12
Salicylic Acid SA induces expression of defense proteins via NPR1 Ethylene and Jasmonic Acid induce an overlapping set of defenses
13
Nitric Oxide Affects many aspects of plant life cycle Primarily made in response to stress Inhibits respiration under anoxia Enhances tolerance of many stresses
14
Nitric Oxide Affects many aspects of plant life cycle Primarily made in response to stress Inhibits respiration under anoxia Enhances tolerance of many stresses Made at least 6 different ways
15
Nitric Oxide Figuring out signaling mechs is ongoing, involves multiple processes
16
Nitric Oxide Figuring out signaling mechs is ongoing, involves multiple processes In germination appears to up-regulate ABA destruction
17
Nitric Oxide Figuring out signaling mechs is ongoing, involves multiple processes In germination appears to up-regulate ABA destruction In guard cells is signaling intermediate Triggers degradation of Ethylene-response factors
18
Nitric Oxide Figuring out signaling mechs is ongoing, involves multiple processes In germination appears to up-regulate ABA destruction In guard cells is signaling intermediate Triggers degradation of Ethylene-response factors
19
Peptides Systemins 18 aa peptides released in response to herbivory
20
Peptides Systemins 18 aa peptides released in response to herbivory
21
Peptides Systemins 18 aa peptides released in response to herbivory Trigger synthesis of jasmonic acid & ethylene in target cells
22
Peptides Systemins 18 aa peptides released in response to herbivory Triggers synthesis of jasmonic acid & ethylene in target cells Some attract parasitoids
23
Peptides Systemins 18 aa peptides released in response to herbivory Trigger synthesis of jasmonic acid & ethylene in target cells Activate defense genes
24
Peptides Systemin 18 aa peptide released in response to herbivory Triggers synthesis of jasmonic acid & ethylene in target cells Activates defense genes hydroxyproline-rich glycopeptides Unrelated structures, but similar size and also activate JA
25
Other Peptides Clavata 3-Wuschel signaling WUSCHEL is a transcription factor made in the “Organizing Center” of the shoot apical meristem Promotes stem cell formation
26
Other Peptides Clavata 3-Wuschel signaling WUSCHEL is a transcription factor made in the “Organizing Center” of the shoot apical meristem Promotes stem cell formation Is secreted and taken up by cells above it, where it induces expression of Clavata 3 which is only made in a few cells of the SAM and promotes differentiation
27
Clavata 3-Wuschel signaling
Clavata 3 which is only made in a few cells of the SAM and promotes differentiation Is secreted and represses WUSCHEL expression in underlying cells This feedback loop controls size of the apical meristem
28
Clavata 3-Wuschel signaling
Clavata 3 which is only made in a few cells of the SAM and promotes differentiation This feedback loop controls size of the apical meristem Acts via at least 4 different receptor protein kinases
29
Clavata 3-Wuschel signaling
Clavata 3 which is only made in a few cells of the SAM and promotes differentiation Acts via at least 4 different receptor protein kinases CLV1 best understood: sets off cascade that results in repression of WUS
30
Other Peptides Clavata 3 type Large gene family ~ 150 members Act over short distances Promote differentiation
31
Other Peptides Clavata 3 type Large gene family ~ 150 members Act over short distances Promote differentiation
32
Other Peptides Clavata 3 type Large gene family ~ 150 members Act over short distances Promote differentiation Act via Pm-bound receptor protein kinases
33
Carbohydrates Cell wall fragments mainly involved in stress signaling
34
Carbohydrates Cell wall fragments mainly involved in stress signaling Released by pathogens digesting cell walls
35
Carbohydrates Cell wall fragments mainly involved in stress signaling Released by pathogens digesting cell walls Can also inhibit cell growth Role in normal development is uncertain
Similar presentations
