auxin and other signals on the move in plants
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AUXIN AND OTHER SIGNALS ON THE MOVE IN PLANTS. Chairman:Student: Dr. P. BalasubramanianS. Saravanan Professor.08-807-003. Auxin. They are a class of plant growth substance and morphogens - PowerPoint PPT PresentationTRANSCRIPT
AUXIN AND OTHER SIGNALS ON THE
MOVE IN PLANTS
Chairman: Student:Dr. P. Balasubramanian S. SaravananProfessor. 08-807-003.
Auxin
They are a class of plant growth substance and morphogens
An essential role in coordination of many growth and behavioral processes in the plant life cycle
Auxins and their role in plant growth were first revealed by the Dutch scientist Frits went
About the AuxinDerive their name from the Greek word
"auxano“ -"I grow/increase”.The first of the major plant hormones to be
discoveredTheir patterns of active transport through
the plant are complexThey typically act in concert with, or in
opposition to other plant hormones
Molecular levelAn aromatic ring and a carboxylic acid
group.The most important member of the auxin
family is Indole – 3 - acetic acid(IAA).It generates the majority of auxin effects in
intact plants, and is the most potent native auxin. However, molecules of IAA are chemically labile in aqueous solution, so IAA is not used commercially as a plant growth regulator.
(Taiz and Zeiger, 1998)
Naturally-occurring auxins include 4-chloro-indoleacetic acid,phenylacetic acid (PAA) and indole-3-butyric acid (IBA).
Synthetic auxin analogs include 1-napthaleneacetic acid (NAA),2,4-dichlorophenoxyacetic acid (2,4-D), and others.
Gallery of native AuxinsIndole -3-acetic acid (IAA)
Indole -3-butyric acid (IBA)
4-chloroindole-3-acetic acid (4-CI-IAA)
2-phenylacetic acid (PAA)
Gallery of synthetic Auxins
2,4-dichlorophenoxyacetic acid (2,4-D)
α-napthaleneacetic acid (α-NAA)
2-Methoxy-3,6-dichlorobenzoic acid(dicamba)
4-Amino-3,5,6-trichlorolinic acid (tordon or picloram)
α-(p-Chlorophenoxy)isobutyric acid (PCIB, an antiauxin)
Molecular mechanism
Auxins directly stimulate or inhibit the expression of specific genes
It induces transcription by targeting for degradation members of the Aux/IAA family of transcriptional repressor proteins, The degradation of the Aux/IAAs leads to the derepression of Auxin Respose Factors -mediated transcription.
Aux/IAAs are targeted for degradation by ubiquitination, catalysed by an SCF-type ubiquitin-protein ligase
Cellular level
Is essential for cell growth, affecting both cell division and cellular expansion
Specific tissue, auxin may promote axial elongation (as in shoots), lateral expansion (as in root swelling), or isodiametric expansion (as in fruit growth)
Promoted cell division and cell expansion may be closely sequenced within the same tissue (root initiation, fruit growth)
Location of AuxinIn shoot and root meristematic tissue
In young leaves
In mature leaves in very tiny amounts
In mature root cells in even smaller amounts
Transported throughout the plant more prominently downward from the shoot apices
Biosynthesis of AuxinIndole pyruvic acid pathway
Tryptamine pathway
Indole acetaldoxime pathway
Effects
Wounding response
Root growth and development
Apical dominance
Ethylene biosynthesis
Fruit growth and development
Flowering
Brief viewThe plants have specialized transport
pathway
Xylem flow from root to shoot
phloem flow from photosynthetic active tissue
Process based on inter cellular transport mechanism
Plant life strategy Regulation of plant size and architecture
Regulating and coordinating plant growth and development process
Transport mechanism include;1.Vascular networks2.Intercellular transport
Transported substances
The substances get transported plant by one or several transport mechanism
The mineral elements to form inorganic to organic
Transported mechanism regulated by external and internal factors
Types of transport
Long distance transport
Short range transport
Long distance transport
The xylem and phloem constitute vasculature based transport and continuous tubular columns
Xylem essential for structural and maintain body height
Phloem sieve elements connected into long sieve tube
In shoot system- collateral vascular bundles
In root system- bilateral symmetry
Long distance transport
Short range transport
Apoplastic transport
Symplastic transport
Transcellular transport
Apoplastic transport
The transport of molecules through from root surface to endodermis
It can control by casparian strip
This structure restrict entry of pathogen, nutrients into out from the vasculature
An example of ABA
Symplastic transport
Connect the cytoplasm of two neighboring cells directly through the plasmodesmata
Symplastic domain vary in size during development
It is important in non-cell autonomous signaling
It is control by plasmodesmata pore
Transcellular transport
The movement of molecule from cell to cellIt regulate and integration of various signalSignal regulating the expression or activity
of transporterThere are two main transmembrane
transport mechanism viz,1.Import epidermal cell and export from
endodermal cell2.Polarly localized plasma membrane
Intercellular pathway
Boron transport
Phloem based transport chemiosmotic model for
polar auxin transport
PIN polar localization during embryo and root
development
Conclusion