Plant Gene Structure and Transcription Factors

• Plant nuclear genomes are organized at multiple levels, dependent on the cell cycle.
• Levels of organization include DNA double helix, DNA wound around a histone core (nucleosome), nucleosome compaction (higher order chromatin structure), and further compaction into metaphase chromosomes.
• Plant genes have core promoters, additional gene regulatory regions upstream, transcribed regions, coding sequences (exons) interrupted by non-coding sequences (introns), and 5' and 3'untranslated regions (5'UTR and 3'UTR).
• Signal transduction pathways often target transcription factors.
• Developmental or environmental signals can impact regulatory transcription factors.
• Most genes are regulated at the transcriptional level.

Transcription Factors

• Transcription factors (TFs) are proteins binding to gene regulatory regions (DNA sequences), activating gene transcription.
• Transcription factors typically possess a DNA-binding domain for recognizing and binding gene regulatory sequences.
• Transcription factors typically possess a protein-binding domain for binding to other proteins involved in regulating transcription.
• Transcription factors are classified by their DNA-binding domains.
• Major categories of TFs include helix-turn-helix, basic leucine zipper, zinc finger, homeodomain, MADS box, and MYB TFs.
• Combinations of regulatory TFs can bind to genes.
• Gene expression is mainly regulated by regulatory sequences, which regulate gene transcription.
• How gene expression is regulated includes: Developmental or environmental signals, basal/regulatory TFs and activate regulatory TFs.

Gene Regulation Summary

• Transcription of many plant genes is differentially regulated by developmental and environmental signals.
• These genes have a core promoter and additional gene regulatory sequences (AGRS) upstream/downstream.
• AGRS are DNA sequences that serve as binding sites for proteins, specifically transcription factors (TFs).
• TFs may be activated or made available for binding through developmental or environmental signaling mechanisms.
• Regulatory TFs bind to the gene regulatory sequences of target genes.
• Interactions between TFs and regulatory sequences determine events at the core promoter of target genes, including activation, modulation, or silencing of gene expression.
• Environmental or developmental signals can affect the transcription of multiple genes at once (e.g., cold-responsive genes in Arabidopsis).
• Genes regulated by the same signaling mechanisms share a similar regulatory region recognized by the same regulatory TFs.
• Most signal transduction pathways in animals induce a response through directly activating TFs that act as regulators of gene expression.
• Some signal transduction pathways (STPs) in plants induce a response by directly activating TFs.
• Most plant STPs induce a response by removing repression of TFs, exemplified by the auxin, gibberellic acid, jasmonic acid, and light signaling pathways.
• Most plant STPs induce changes in gene expression by removing TF repressor proteins.

Receptors

• Cell receptors generally consist of a ligand binding domain and an effector domain.
• Broad classes of receptors are conserved across kingdoms.
• Three main types of receptors include receptor-linked kinases, G-protein coupled receptors, and ion-channel linked receptors.
• The plasma membrane is a major site of signal perception.

G-Protein Coupled Receptor Systems (GPCRs)

• G protein-coupled receptor systems (GPCRs) are the largest and most diverse superfamily of membrane receptors in eukaryotes.
• GPCRs interact with G proteins at the plasma membrane.
• A typical structural organization of GPCRs includes N-terminal and C-terminal regions and a highly conserved seven-transmembrane core backbone.
• G proteins are specialized proteins that can bind guanosine triphosphate (GTP) and guanosine diphosphate (GDP), and are heterotrimeric proteins (α, β, γ).
• Active G proteins relay messages in the cell by interacting with other proteins involved in signal transduction.
• Mammals possess between 500 and 1,000 GPCRs.
• Humans use GPCRs for sensory perception (vision, smell, flavours).
• The Arabidopsis genome contains only a handful of putative GPCRs that are not well understood.

Ion Channel-Linked Receptors

• Ion channel-linked receptors are multi-subunit membrane-spanning proteins.
• They allow inorganic ions to flow across the membrane.
• Ligand binding to the receptor causes the channel to open
• specific ions (Na+ or Ca2+) flow across the membrane.
• Changes in ion concentration trigger cellular responses.
• Ligand dissociates and the channel closes
• Plants lack ion channels that function as sensors of external ligands.
• Sensing mechanical stimulation in plants involves calcium ion channels.
• Ion channel-linked receptors are important in animal nervous systems at synapses between nerve cells.

Receptor-Linked Kinases (RLKs)

• Signal perception in plants relies on plasma membrane-bound or intracellular receptor-linked kinases (RLKs).
• RLKs phosphorylate target proteins, often serine/threonine or tyrosine kinase receptors.
• RLKs transduce extracellular signals through phosphorylation of intracellular targets.
• Membrane-bound RLPKs consist of an extra-cellular signal/ligand-binding domain, a transmembrane domain (single α helix), and an intracellular kinase domain.
• Activation is a 2-step process signal (ligand) binding -> dimerization
• Kinase Activation
• Receptor linked protein Kinases, are the largest group of membrane receptors in plants (>600 in Arabidopsis, over 1,100 in rice)
• Examples of such membrane receptors are found in the plant immunity section of B1306.
• Not all receptors are located at the plasma membrane.
• The plasma membrane is no barrier to small lipophilic signalling molecules and many physical cues (e.g. light).
• Some photoreceptors (phytochrome and cryptochrome) are in located in the cytoplasm or nucleus, depending on light conditions.
• Ethylene is detected by receptors on the endoplasmic reticulum membrane.
• Auxin and gibberellin are perceived by soluble receptors in the cytoplasm interact with the cell's protein degradation machinery.

Receptor & Receptor Linked Kinase Summary

• Environmental and developmental signals are perceived by cell receptors.
• Receptors typically consist of a ligand domain and an effector domain.
• Receptors can be membrane-bound or intracellular.
• Three major classes of plasma membrane-bound receptors are: receptor-linked protein kinases, G protein-coupled receptors, and ion channel receptors.
• RLPKs are the largest group of membrane receptors in plants.
• Membrane-bound RLPKs consist of an extra-cellular signal/ligand-binding domain, a transmembrane domain, and an intracellular kinase domain.
• Many plant receptors are located within cells – on ER membrane (ethylene), in the cytoplasm (auxin and GA), or in the cytoplasm or nucleus (phytochrome and cryptochrome).

Signal Transduction

• Signal transduction is the transfer of information from the site(s) of perception to the site(s) of response.
• Intracellular signal transduction can involve very few steps, such as activated photoreceptors relocating from the cytoplasm into the nucleus and directly affecting transcription factors (no secondary messengers).
• Signal transduction can also involve many steps using secondary messengers and relay proteins.
• Calcium (Ca2+) is the most ubiquitous second messenger in plants.

Intracellular Calcium

• Cytoplasmic [Ca2+] is low (100-350 nM).
• Vacuole and ER [Ca2+] : 1-2 mM
• Cell wall [Ca2+]: 0.5-1 mM.
• Ca2+ is actively pumped out of the cytoplasm and actively imported by the ER and other cellular compartments.
• Many cell surface receptors activate the enzyme phospholipase C (PLC).
• PLC hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) to form IP3 and diacylglycerol (DAG), which are two classic secondary messengers.
• IP3 diffuses within the cell and binds to the IP3 receptor, a Ca2+ channel.
• IP3 binding releases Ca2+ into the cytoplasm, resulting in a Ca2+ spike in response to a signal.
• Ca2+ release from the endoplasmic reticulum occurs through phospholipase C (PLC).
• Spikes in cytoplasmic [Ca2+] (up to 1 µM) can occur in response to biotic and abiotic stimuli like pathogen infection, nodulation factors, the hormones GA and ABA, red and blue light, UV-B radiation, temperatures, touch, wind, and changes in the gravity vector, and anerobic, drought and salt stress.
• Ca2+ can directly bind to target proteins and regulate them (kinases).
• Ca2+ can bind to calmodulin proteins, which are [Ca2+] sensor proteins.
• Ca2+/calmodulin activates target proteins through direct binding or phosphorylation.
• Targets can include proteins in transcription factors, protein kinases and enzymes producing reactive oxygen species (ROS).
• Ca2+ pumps/exchangers remove cytosolic Ca2+ to terminate signaling.
• Removal of Ca2+ from the cytosol against its electrochemical gradient to the apoplast or intracellular organelles requires energized 'active' transport, catalyzed by Ca2+-ATPases.
• Protein phosphorylation is a major signal transduction mechanism.
• Many relay molecules in signal-transduction pathways are protein kinases.
• Combinations of different kinases within a pathway create a mitogen-activated protein kinase (MAP kinase) cascade.
• When no activating signal is present, phosphatases predominate and the signal transduction cascade and cellular response is shut down.

MAPK Cascades

• MAPK cascades function in diverse signal transduction pathways.
• MAPK cascades exist in all eukaryotic cells.
• Plant MAPK cascades are involved in almost all aspects of plant growth/development and response to environmental stimuli, including pathogen attack.
• The core cascade consists of a series of three kinases: a MAPKK kinase (MAPKKK), a MAPK kinase (MAPKK), and a MAPK.
• Signalling through the cascade is induced by activation of the MAPKKK.
• Plants have a complex network of kinases involved in a range of diverse processes.
• These processes include hormone signalling, responses to stress and responses to pathogens.
• Arabidopsis has about 60 MAPKKKs, 10 MAPKKs, and 20 MAPKs, giving the potential for thousands of MAPK cascade-forming combinations.
• Individual upstream signals can activate multiple MAPK cascades.
• Individual kinases can be activated by multiple upstream signals. Summary
• Many signal transduction pathways involve intracellular second messengers
• Ca2+ is a significant second messenger in plant cells
• Ca2+ can regulate target proteins directly or via calmodulin
• Many relay molecules in signaling pathways are protein kinases
• MAPK cascades are involved in many plant signal transduction pathways including those responding to stress, pathogens, and drought.
• In plants, signal transduction pathways are a complex web of signaling interactions.

Light as a Signal

• The source of energy that drives photosynthesis is NOT light acting as an environmental signal
• Responses to light are critical for plant success.
• Light acts as a signal for key events in plant growth and development.
• Plants can detect not only the presence of light but also its direction, intensity, quality, and duration.
• Photomorphogenesis describes the effect of light on plant growth and development.
• Adaptive responses include phototropism, shade avoidance, and biosynthesis of photoprotective pigments (e.g., carotenoids) in response to UV-B irradiation.
• Cellular responses to light includes regulates the position of chloroplasts (maximize light capture; minimize photodamage) and controls opening and closing of the stomata
• Plant grown in shade conditions display stem elongation.
• A tightly folded apical hook characterizes dark-grown seedlings that are etiolated, characterized by an elongated hypocotyl, and closed/yellow cotyledons.
• Hypocotyl elongation is inhibited, hook and cotyledons open, and chlorophyll is synthesized once exposed to the light de-etiolating the seedling

Light Developmental Signals

• Light inhibits hypocotyl length and internode length.
• Light promotes radial expansion of the hypocotyl and the stem.
• Light promotes apical hook unfurling during de-etiolation.
• Light promotes cotyledon expansion and leaf expansion.
• Light promotes chlorophyll biosynthesis.
• Mutants can help answer biological questions
• Individuals that contain specific changes in their DNA sequence are called mutants.
• Mutations in genes can knockout gene function
• Use of mutants can infer biological functions.
• Mutagenizing a population, screening mutants, and their specific phenotype, identifying the gene helps scientists infer the function of a gene.
• The cop1 mutant in Arabidopsis grown in the dark looks identical to light grown wild-type seedlings.

COP1

• COP1 is the Constitutive Photomorphogenesis 1 gene.
• The cop1 mutant exhibits aspects of seedling photomorphogenesis when grown in the dark. The role of COP1 in wild-type plants is to actively repress seedling photomorphogenesis in the dark.
• Light removes repression of photomorphogenesis
• COP1 plays a role in repressing photomorphogenic responses.
• COP1, codes for a Really Interesting New Gene (RING)-finger E3 ubiquitin ligase.
• Activity of COP1 depends on its interaction with SUPPRESSOR OF PHYA-105 (SPA) proteins.
• COP1/SPA are part of at least two CUL4-based E3 ubiquitin ligase complexes
• E3 ubiquitin ligases polyubiquitinate proteins and target them for proteasome-mediated degradation.
• A single ubiquitin molecule is transferred on a ubiquitin activating enzyme (E1) in an ATP-dependent reaction.
• The ubiquitin molecule is transferred from E1 to a ubiquitin conjugating enzyme (E2).
• In the final step, ubiquitin is transferred to the protein substrate in a process mediated by an E3 ubiquitin ligase
• Poly-ubiquitinated proteins are targeted to the proteasome for degradation.
• In the dark COP1/SPA ubiquitinates and promotes the degradation of TFs that control the expression of light regulated genes (e.g. HY5).
• Light signals removes this repression signals.
• Some STPs induce a response by directly activating TFs that act as regulators of gene expression and are regulatory TFs in plants.
• Most plant STPs induce a response by removing repression of TFs.
• An example of repressor proteins includes: Repressed RTF-JA
• Auxin signaling, Gibberrellic signaling, Jasmonic acid signaling and Light signaling

Light-Signalling summary

• In plants photomorphogenic responses including COP1/SPA are actively repressed
• COP1/SPA are part of at least two CUL4-based E3 ubiquitin ligase complexes that ubiquitinate and promote the degradation of TFs that activate the expression of light regulated genes (e.g. HY5) in the dark.
• Light signals stop this COP1/SPA-mediated degradation of TFs that are needed to activate light regulated genes
• In the light TFs such as HY5 have access to gene regulatory sequences and activate the transcription of many light regulated genes

Light Perception

• Light perception involves receptors (photoreceptors) that can detect specific wavelengths of light.
• Plants have several photoreceptors that can detect light.
• The UVR8 receptor perceives UV-B light (280 nm to 320 nm)
• Cryptochrome receptors perceive UV-A and blue light (320 nm to 500 nm).
• Phototropins and Zeitlupe receptors perceive blue light (350 nm to 500 nm).
• Phytochrome receptors perceive red and far-red light (620 nm to 800 nm)
• Most photoreceptors consist of proteins (holoproteins) bound to light absorbing pigments (i.e. chromophores.
• The spectral sensitivity of each photoreceptor depends on its chromophore.
• Downstream signalling is initiated in response to light absorption, and is mediated by the activated photoreceptor.
• The light-sensitivity of each photoreceptor depends on its chromophore.

Different Chromophores

• UVR8: Tryptophans on the protein
• Cryptochrome: Phytochromes: Flavin adenine dinucleotide (FAD)
• Phototropins and Zeitlupe: A flavin mononucleotide (FMN)
• Phytochromes: (pterin 5,10-methyltetrahydrofolate (MTHF)
• A linear tetrapyrrole called phytochromobilin

Blue light photoreceptors

• Blue light photoreceptors respond to the blue/UV-A region of the spectrum (320-500 nm), and are Cryptochromes and Phototropins
• Cryptochromes are UV-A/blue photoreceptors
• First blue-light photoreceptors to be characterized
• Identified in Arabidopsis, later discovered in a wide range of organisms (cyanobacteria, ferns, algae, Drosophila, mouse, humans).
• The only photoreceptors present in all evolutionary lineages ranging from bacteria to mammals
• Important in the establishment of animal and plant circadian rhythms.
• CRYs are involved in regulating almost every stage and aspect of the plant life cycle which includes the circadian clock, de-etiolation, flowering, guard cell development, stomatal opening, senescence, and pathogen responses
• Arabidopsis has three cryptochrome photoreceptors - CRY1, CRY2 and CRY3 and Plant CRY1 and CRY2 are best understood
• CRY1 and CRY2 are are soluble proteins – found in the cytoplasm and nucleus and contain two chromophores: a flavin adenine dinucleotide (FAD) and the pterin 5,10-methyltetrahydrofolate (MTHF).
• A FAD is the primary chromophore
• CRY1 and CRY2 exist as inactive monomers in darkness and have overlapping, but also distinct functions
• Both CRY1 and CRY2 have important functions during seedling de-etiolation in blue light – some redundancy in their role and Cryptochrome 2 plays a role in blue-light mediated perception of flowering time
• A cry2 mutant causes in flowering
• CRY Structure consists of two domains, a highly conserved N-terminal photolyase homology region (PHR) and a more divergent, unstructured CRY Carboxy Terminus (CCT or CCE domain); The PHR domain binds the primary chromophore, FAD, and is responsible for light detection by the photoreceptors and mediate oligomerization of CRYs which is essential activity
• CCT domain is important for the blue light-induced interaction with signalling proteins

Cryptochrome photo-activation

• Cryptochromes exist as inactive monomers in darkness.
• Both CRY1 and CRY2 are phosphorylated in response to blue light by a family of four related Ser/Thr protein kinases
• Known as the PHOTOREGULATORY PROTEIN KINASES (PPK1–PPK4)
• Photoexcited cryptochromes undergo oligomerization to become biochemically and physiologically active (homo-or heteromers).
• Regulate transcription factor activity indirectly via the COP1/SPA E3 ubiquitin ligase complex or directly by activating regulatory TFs
• Phosphorylated isoforms of both CRY1 and CRY2 can interact with the COP1/SPA complex that polyubiquitinates multiple transcription factors acting in the various light responses
• Photoactivated CRY1 relocates to the nucleus and cause the disassembly of a ubiquitin ligase complex and COP1 removal from the nucleus

Additional notes on CRY

• TFs that regulate light-regulated (photomorphogenic) genes are stabilized in the nucleus and facilitate target gene expression
• blue light stabilized TF's genes involved in regulating hypocotyl and internode elongation (CRY1 and CRY2), flowering time (CRY2), and Genes involved in anthocyanin biosynthesis (CRY1)
• Photoactivate CRYs can also directly interact with several transcription factors
• Photoactivated CRY2 interacts with a family of CRYPTOCHROME-INTERACTING BHLH (CIB) transcription factors to regulate flowering time in Arabidopsis
• Photoactivated CRY2 interacts with other CIB TFs to regulate seedling de-etiolation.
• Cryptochromes are photoreceptors that respond to the blue/UV-A region of light (320-500 nm).
• Arabidopsis has three cryptochrome photoreceptors - CRY1, CRY2 and CRY3
• CRY1 and CRY2 soluble proteins are partitioned between the cytoplasm and nucleus
• These exist as inactive monomers in the dark.
• Light activated cryptochromes undergo homo- and hetero-oligomerization to become biochemically and physiologically active.
• Activated cryptochromes can remove COP1-mediated repression of TFs needed to transcribe blue light regulated genes, e.g. HY5 and CONSTANS (CO)

UVR8

• Activated Cryptochrome can also directly interact with CIB TFs and positively regulate light regulated genes, e.g. FLOWERING LOCUS T (codes for a TF required to activate downstream genes involved in flowering).
• UVR8 is responsible for UV-B and photomorphogenic responses (tryptophan)
• Phototropins and Zeitlupe chromophores = A flavin mononucleotide (FMN)
• Phytochromes linear tetrapyrrole called phytochromobilin
• Inactive UVR8 and exists as inactive dimers in the dark.
• UV-RESISTANCE LOCUS 8 (UVR8) photoreceptor activates large changes in gene expression, which leads to morphological adaptations and the production of flavonoids that act as UV-B protectant ‘sunscreen'.
• Photoactived UVR8 moves into the nucleus, and Activates UVR-8 inactivates the COP1/SPA complex that polyubiquitinates multiple transcription factors
• HY5 activates UV-B responsive genes in the flavonoid biosynthesis pathway, Flavonol synthase 1 (FLS) and Chalcone synthase (CHS) genes are included
• UVR8 photoreceptors respond to the UV-B region of light (280-320 nm) lacking a separate chromophore
• UVR8 exists as inactive dimers in the dark.
• Light activated UVR8 undergoes monomerization to remove COP1-mediated repression of TFs

Phototropins & Zeitlupe

• A flavin mononucleotide (FMN)
• Phytochromes: A linear tetrapyrrole called phytochromobilin:
• Inactive UVR8 is a dimer and photoactivated UVR8 is a monomer: Absorption
• Phototropins are Involved in light regulation of: Phototropism,Light-induced chloroplast movement and Stomatal openings

Phototropins in Arabidopsis

• Arabidopsis has two phototropin receptors - Phot 1 and Phot2 - Cell membrane localized The phot1 phot2 double mutant is also impaired in other blue-light responses No chloroplast movement and no stomatal in blue light
• Phototropins are involved in regulating phototropism, stomatal opening and chloroplast migration
• Phototropins contain 2 photosensory LOV which bind flavin mononucleotide.
• A C-terminal part consists of a serine-threonine kinase
• In the dark phototropins are located on the plasma membrane, Membrane localization depends on the c-terminus
• Blue light promotes autophosphorylation and partial internalization of Phot1 and Phot2 to the golgi appratus .
• Phototropins trigger asymmetric auxin distribution

Phototropin Signalling Summary

• Arabidopsis has two Phototropin photoreceptors - PHOT1, PHOT2
• Phototropins and have been shown to be plasma membrane - bound serine/threonine kinases-linked receptors

• redistribution of auxin in case of phototropic response

• cells on side of the stem elongate more relative to cells on the other side

• stem bends towards unidirectional light

• Activated blue light and UV-B photoreceptors
• Induce a response by removing TF’s Cryptochrome activated signalling In Arabidopsis:
• Activated signalling requires the induction a response by directly activating TFs that act as regulators of gene expression
• cryptochrome activated signalling is needed to Induce signaling of a response that does not directly activate TFs

Phytochrome

• Red light generally activates a phytochrome response; but the effect photo-reversibility can be reversed with a far-red light (700-780 nm) Soon after red treatment

Phytochrome structure

• Dimeric chromoproteins in which the two apoproteins are covalently bound to phytochromobilin, a linear tetrapyrrole chromophore The protein : a molecular mass of about 124 kDa (dimer 250kDa) and Serine/threonine kinase activity.

Phytochrome interactions

• A intracellular receptor that that is the cytoplasm and nucleus
• The chromophore undergoes a cis-trans isomerisation at
• Pr & PFR exist in a photostationary/equilibrium and has absorption spectra
• Saturating irradiation: fully drives into PR as PR or PFR

More details On PFR

• Saturating Red irradiation: results to 15% PR and 85% PFR Saturating Far Red irradiation : results in : 97% R -3% PFR. These is partitioned between the cytosol and the nucleus Biosynthesized as the inactive Pr forms Cytoplasm – phytochrome proteins dimerise in the inactive PR state Photoactivation to PFR associated with conformational change in the dimer so the - PFR moves from the cytosol into the nucleus.

• Phytochrome Regulates a set of transcription factors

Phytochromes

• Extensive changes in gene expression: expression as the initial exposure of seedlings to light.
• Phytochrome signals largely depending on modulation of transcription factor stability.

13. (PIFs promote degradation of TFs
14. That are negative regulators of light responses by phosphoryltaion and ubiquitin
15. Stabilizes transcription factors: of positive regulators • Pfr aggregates into discrete subnuclear foci
16. Photobodies colocalizes signaling components
17. that at and negative

Signaling molecules summary- Phytochrome

• Phytochrome: responds primarily to red light and far-red light & is critical almost every aspect of plant growth and development and exists interconvertible forms: PR which absorbs red light and PFR absorbs far - red

Where phytochrome acts

• Phytochrome response occurs in both in the cytosol and the nucleus
• Pfr forms large aggregates within photobodies colocalizes key signalling components
• Pfr signal then stimulates degradation and transcription: of negative light response, or stimulate. Pfr signalling Stabilizers: activators.
• Arabidopsis plant: 5 genes of a family
• PHYA labile under light:
• PHYB and others are stable

More Phytochrome facts

PHYA labile

• Seeds that imbibe and are in etiolated seedling

PHYB involved regulating

• Resoponsible PHYA - early
• Plays little.
• Redundant VLF and seedling:
• Seed: senesitive
• VLF

Phytochrome: Key Information

• PRA = absorption 36. PRA shows some activity after any irradiation at VLF *VLF
• • Arabidopsis: phenotype: all:
• Deficient in chlorophyll
• Deficient in photo-reversible
• flowering
• Unable shade Phenotype lower: 16 C later: 16 C earlier: 22 CC phyb Shade

Summary on light interactions

• PFR medates responses as its presence modulates the direct responses
• MAPK
• Response Potential Membrane ,
• Double

Photoperiods

• Photoperiod requires the combined. phyA double do not . Cry
• Blue light
• PhB B and is light in seedlings Apoproteins

Further information

• Responses modulated TF’s, some by membrane signalling

The most dramatic process : Flowering

• Change in plants of programme
• Apical produces Vegetative : or
• The most of reproductive flowering
• Seeds and and as for

Reproduction details

Major change

• Flowering at are a
• Levels regulators

Details about flowering

Flowering is for to ensure

What is required ?

1. of : • Days of A1 of a

• Is the part perception Is photoperiodic (leaf

Additional Notes about Flowering

A) plant of

1- In represses mutants dependant) photoperiod

Details On the Flower

1. of and represses represses

2- Is in (23oc) PHYA A

What where

• It’s leaves.

3- Is

• (SAM -vegetative)

Flowering Summary

1. In (leaf

Summary about PFL

• • • and

• Plants can duration

Details Of SAM

• Photoperiod the (23oc1)

FLOWERING & LIGHT

• 1 The - PHT
• • Photoperiod. A and CO long in
• ***Details ON FLOWERING
• There so protein at promote 1 in days- C = FL,

1. Of is under. and signal

Arabidopsis Specific notes

1. Tf and over time CO of signal

flowering LOCUS T

FT in the move: - In the

More Info On PFL

1. Plants at in -The light the external

Additional factors

1. Is of the with in 1

Flowering, cont’d

Floral and a

• And 1. That a days.
• And as

Details About Photoperiod

• 1 of in that plant

Important Notes

• *1 of are temperature the 8
• 1 of is does
• Is of FLC

(2 FLC CRY2 PHYA CO FT SOC1 FD

1 -

• • **1 F at