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Leshormonesdecroissance:auxines
Auxine naturel
Auxinessynthtiques
er c e s ec
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Rlephysiologiquedesauxines
Contrledeladominanceapicale
+Auxine auxine
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Effetsdauxinessurlapex(coloptile),racineet(fruit)
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Lerledesauxinesdanslenracinementest
connudans
1930s
Impossibled'aff icher l'image.Votreordinateur manquepeut-tredemmoirepour ouvrir l'imageou l'imageestendommage.Redmarrezl'ordinateur,puisouvreznouveau lef ichier.Si lex rougeesttoujoursaff ich,vous devrezpeut-tresupprimer l'imageavantdelarinsrer.
Impossibled'aff icher l'image.Votreordinateur manquepeut-tredemmoirepour ouvrir l'imageou l'imageestendommage.Redmarrezl'ordinateur,puisouvreznouveau lef ichier.Si lex rougeesttoujoursaff ich,vousdevrezpeut-tresupprimer l'imageavantdelarinsrer.
Adventitiousrootsare
stemstreated
with
auxin
Amorerecentexperimentinwhich
radishroots
were
dipped
into
auxin
andinitiatedlateralrootsata
frequencyproportionaltoauxin
concentration. M
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Letransportpolairdesauxinesestconnudans
1930s
Asegmentcutfroma
Whenthesegmentis
inverted,it
is
unable
to
coleoptilecanmove
auxinfromtiptobase.
totip.
Thisexperiment,
carried
out
by
The
u er
a ar
block
was
H.G.Vander Weij revealedthat
auxinintheshootistranslocated
fromtiptobase.
loadedwithauxin,whichthe
segmenttranslocatedtothe
lowerblock.
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Fonctionphysiologiquedesauxines
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Lasynthse,letransportetlasignalisationdes
auxines
Catabolism Conjugation
Synthesis IAA Transport Perception
(receptor)
TFactivation/
inactivation
Target
genes
Biological
Functions
Les effets des auxines dpendent de leur synthse, transport,perception, signalisation et contrle de lexpression de gnes.
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Auxinresponsepathway feedback
regulation
Catabolism Conjugation
Synthesis IAA Transport Perception
(receptor)
TFactivation/
inactivation
Target
genes
Biological
Functions
Les voies designalisationsont contrles
extensivement pardesrgulations feedbackpositives
etnegatives.
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LabiosynthsedIAA
ChezAgrobacteriumtumfaciens
TAMIPA
IAAId
dgradation
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Lhomostasiedauxinesestcontrlaussiparla
conjugaisonet
la
dgradation
IAA
GH3 genes
are auxin-Arabidopsis
Riz
(GH3 genes)induced
GH3.13
surexpressionWildtype
GH3.13Wildt e
surexpression dune enzyme de conjugaison
surexpression
GH3 rduit le niveau dauxine.
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Catabolism Conjugation
Synthesis IAA
maintenuepar
la
synthse,
le
catabolisme,laconjugaisonetle
trans ort.
Transport
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letranopsrtlonguedistancesviale
phlome.
transporteurs
protiques.
.
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Lemouvementdauxineaucotombrag
IAAaccumulatesonthe
shadedsideof
phototropically
Increasedauxinpromotes
cellelongationontheshaded
side causin bendin toward
DR5::GUS
oleraceahypocotyls. thelight.
CelllengthAuxininduced
transcriptionoftheDR5
Auxin
p omo e se eva e on
thedarksideofthis
phototropically
stimulatedArabidopsis
concen ra onhypocotyl.
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PlusieursmutantsdArabidopsis onttidentifis
ayantdes
rsponses
gravitropiques
anormales
pin2
WT
pin2WT Anal sis of these mutants has identifiedseveral types of auxin transport proteins, aswell as proteins that regulate their activity anddistribution.
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Lemouvementdesauxinesviades
transporteursprotiques
defflux
et
dinflux
LesPIN:mouvement
directionneldauxines
vers
ABCB
ext r eur e ace u e.
ABCB
Celltocell
polar
auxin
transport
Lestransporteurs
dinflux
contribuentau
mouvement
Lestransporters B B
contribuent autransport
dauxine dans de
ABCB
cytoplasme.ren es rec ons
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AUX1 importelauxinedanslacellule
AUX1/LAX
Carrier
mediated
auxin
uptake
Plusieurs gnes desprotines like-AUX1; Auxinuptakeis
mutants.
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LesABCB sontimportantespourletransport
aux ne
PGP
abcb1abcb191abcb19
2 abcb19
2
abcb1WT
ABCB
WT abcb191
Lossoffunctionofsome ABCB
genes causesdiverse
phenotypes
Arabidopsisencodes21ABCB
proteins,manyofwhichare
necessar for ro er auxinincludingdwarfismandaltered
tropisms.
transport.
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Lesprotines PIN nommes selon le
phnotype dupin
formedmutant
pin-formed, which has amutation in the PIN1 gene,makes some abnormal leavesand then a bare inflorescence.
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LesPIN auxinsontparunelargefamilledegnesavec
desprofiles
dexpression
spcificques
PIN
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LesprotinesPINsoriententdefaonasymmetrique
ans
esce u es
PIN1localizesto
thelower surface
ofroot
cortex
cells
Root
Base
forauxin
flow
from
shootapextoroot
apex.
Root
Apex
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LesdiffrentesPINsoriententdiffremment
PIN2 localizestothelower
surface of root cortex cells andtheuppersurfaceofepidermal
cells.
PIN2isfunctions
pr mar y n e
redistributionof
auxinduringroot
gravitropism
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LadistributiondesPINcontribuentla
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LtatdephosphorylationdesPINsaffecteleurdistribution
pro e nsarep osp ory a e y
theproteinkinasePINOID(PID)and
dephosphorylatedby
the
protein
PPPP
.
P P
Control Staurosporine
treated
Staurosporineinhibitsprotein
kinases
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Leseffetsdesauxinessontmedisparaumoins2types
ofrcepteurs
Perception
(receptor)ABP1
IAA
Perception
(receptor)SCFTIR1
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AUXINBINDINGProtein1est ncessaire pourla
divisionet
lexpansion cellulaire
WildtypeEtOH
induced
LossoffunctionofABP1is
embryo
lethal.
ABP1
antisense Plantswereproducedthat
carryaninducibleantisense
ABP1 gene.They
were
grown
for12daysinnoninductive
conditions.
Atday12,ABP1 wassilenced
andplant
growth
was
severely
restricted.
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LereceptorTIR1estuncomposantducomplexe
SCFTIR1dela
SCF
ubiquitin
ligase
FboxTIR1
auxinreceptor
SKP1
FboxTIR1
protein
SCFcomplex
CUL1
SCFubiquitinligasecomplex
(NamedforSKP1,CUL1andFbox
proteins)
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LescomplexesUbiquitin ligase(E3)
ubiquitinylent lesprotines cibles
Ubiquitine
The F-box protein
ciblecible
recognizes and bindsto the target protein.The complex then
SKP1
rans ers u qu nproteins to the target.
CUL1
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TIR1ncessite lafixationdauxine pour
tre activ
TargetAuxin
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cibleAuxineQuesontlesciblesde
laprotolyse mdie
SCFTIR1?
I II III IV
Lesprotines Aux/IAAetpourleur dgradation
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LademieviedesprotinesAux/IAAesttrscourte
PSIAA6
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Lesprotines Aux/IAArpriment lactivit desfacteurs de
transcriptionappels
Auxin Response
Factors
(ARFs)
III IVDNAbinding
domain
Activation/
repression
domain
an ux pro e ns ave
sequencesimilarityintheirC
terminalregionsthroughwhich
I II IVAux/IAA
III
.
ARFhomodimer
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R ressiondes nes
parIAA/Aux
en
absence
dauxine
Ds rpressiondela
transcription
des
gnes
ARF:FTactivateur
Aux/IAA:rpresseur
Auxineinduitladgradation
desAux/IAA
via
ubqitination.
LadgradationdesIAA/AuxparlAuxinencessitedelaprotineTIRquifonctionnedansE3
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g / p p q
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Rsum
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Commentlesauxines peuventaffecterdenombre
processusdu
dveloppement
de
la
plante?
Perception
(receptor)
Target
genes
Auxin
induced
gene
productsAux/IAAproteins
GH3(auxinconjugation)
Jasmonicacidsynthesis
CKX(cytokinindegradation)
Transcriptionfactors Biological
FunctionsAuxinrepressedgeneproducts
Cellwallproteins
ARRs(Cytokininsignaling)
Transcriptionfactors
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Dfautdanslasynthse,letransportoulasignalisation
causeun
phnotype
identique,
sans
racine
pin1,3,4,7Wildtype yucca1,4,10,11
yucca1,4,10,11,
mp and
pin1,3,4,7mutantsareallrootless
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Inthecurrentmodelforauxin
inducedcellwallelongation,
auxinstimulates
a
lasma
H+ H+
AuxinH+
membraneboundproton
pump,whichacidifiesthecell
wall.H+
H+
Length
Cellwallacidificationis
sufficientto
induce
cell
Time
elongation.
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Lauxinefonctionnecommeunmorphognedanslapex
racinaire
Auxinamount
Cellsatthequiescent
center ex erience
Cellsexperiencinga
lowauxinlevel
thehighestauxin
concentrationsand
remainquiescent.
elongateand
differentiate
Quiescent
Cellsnearthetip
experience
intermediate
auxin
centerlevelsanddivide
frequently
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Lauxinefonctioneaussicommeundclencheurpour
initierdes
vnements
de
dveloppement
Alocalizedauxinmaximum(orminimum)canbesufficientto
n a ea
eve opmen a
even .
ere
ere
n ca es
ce s
triggeredtodifferentiatebyelevatedauxinlevels.
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., ,
The inflorescence meristem of theArabidopsispin1 mutant does not make flowers. Applicationof a spot of auxin (red) triggers organogenesis.
La synthse enforce de lauxine dans une seule cellule
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Lasynthseenforcedel auxinedansuneseulecellule
latrale
Theexperimental
increase
of
auxin
synthesisinonecellissufficientto
triggeralateralrootformation.
Singlecell
biosynthesis
(monitoredby
DR5::GUS .
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Ungradientdauxineformdurantladiffrentiation
cellulairepour
la
formation
de
bois
Cambial
ZonePhloem Tracheids
(xylem)