Growth regulators 1.Auxins 2.Cytokinins 3.Gibberellins 4.Abscisic Acid 5.Ethylene

Growth regulators 1.Auxins 2.Cytokinins 3.Gibberellins 4.Abscisic Acid 5.Ethylene

Growth regulators 1.Auxins 2.Cytokinins 3.Gibberellins 4.Abscisic Acid 5.Ethylene 6.Brassinoteroids

7.Jasmonic Acid 8.Salicylic Acid 9.Strigolactones 10.Nitric Oxide 11.Sugars 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 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

Brassinosteroids Validated by mutants BR synthesis mutants are dwarf & defective rescued by BR BR-insensitive mutants are dwarf & defective dont respond to BR

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 Strigolactones

Growth regulators derived from carotenoids Released from roots to attract endomycorrhizae trigger germination of parasitic plants, e.g. witchweed (Striga asiatica) 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 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

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 Salicylic Acid

Affects plant growth and development Photosynthesis Transpiration ion uptake and transport 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 Salicylic Acid SA induces expression of defense proteins via NPR1

Ethylene and Jasmonic Acid induce an overlapping set of defenses Nitric Oxide Affects many aspects of plant life cycle Primarily made in response to stress Inhibits respiration under anoxia Enhances tolerance of many stresses

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

Nitric Oxide Figuring out signaling mechs is ongoing, involves multiple processes Nitric Oxide Figuring out signaling mechs is ongoing, involves multiple processes In germination appears to up-regulate ABA destruction

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

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 Peptides

1. Systemins 18 aa peptides released in response to herbivory Peptides 1. Systemins 18 aa peptides released in response to herbivory

Peptides 1. Systemins 18 aa peptides released in response to herbivory Trigger synthesis of jasmonic acid & ethylene in target cells Peptides 1. Systemins

18 aa peptides released in response to herbivory Triggers synthesis of jasmonic acid & ethylene in target cells Some attract parasitoids Peptides 1. Systemins 18 aa peptides released in response to herbivory

Trigger synthesis of jasmonic acid & ethylene in target cells Activate defense genes Peptides 1. Systemin 18 aa peptide released in response to herbivory Triggers synthesis of jasmonic acid & ethylene in target cells

Activates defense genes 2. hydroxyproline-rich glycopeptides Unrelated structures, but similar size and also activate JA Other Peptides 1. Clavata 3-Wuschel signaling WUSCHEL is a transcription factor made in the Organizing

Center of the shoot apical meristem Promotes stem cell formation Other Peptides 1. 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 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 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 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 Other Peptides 1. Clavata 3 type Large gene family ~ 150 members

Act over short distances Promote differentiation Other Peptides 1. Clavata 3 type Large gene family ~ 150 members Act over short distances

Promote differentiation Other Peptides 1. Clavata 3 type Large gene family ~ 150 members Act over short distances Promote differentiation

Act via Pm-bound receptor protein kinases Carbohydrates Cell wall fragments mainly involved in stress signaling Carbohydrates Cell wall fragments mainly involved in stress signaling

Released by pathogens digesting cell walls 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

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