Download Functional markers in plants

AUXIN AND OTHER SIGNALS
ON THE
MOVE IN PLANTS
Chairman:
Dr. P. Balasubramanian
Professor.
Student:
S. Saravanan
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 Auxin
 Derive their name from the Greek word "auxano“ -"I
grow/increase”.
 The first of the major plant hormones to be discovered
 Their patterns of active transport through the plant are
complex
 They typically act in concert with, or in opposition to other
plant hormones
Molecular level
 An 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 Auxins
 Indole -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 Auxin
 In 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 Auxin
 Indole pyruvic acid pathway
 Tryptamine pathway
 Indole acetaldoxime pathway
Indole pyruvic acid pathway
Tryptophan
Indole pyruvic acid
Indole acetaldehyde
IAA
Tryptamine pathway
Tryptophan
Tryptamine
Indole acetaldehyde
IAA
Indole acetaldoxime pathway
Tryptophan
Indole acetaldoxime
Glucobrassicin
Indoleacetonitrile
IAA
Effects
 Wounding response
 Root growth and development
 Apical dominance
 Ethylene biosynthesis
 Fruit growth and development
 Flowering
Brief view
 The 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 networks
2. 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 cell
 It regulate and integration of various signal
 Signal regulating the expression or activity of transporter
 There are two main transmembrane transport mechanism
viz,
1. Import epidermal cell and export from endodermal
cell
2. 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