Transcript Her rash hand in evil hour, Forth reaching to the fruit

ethylene, and it’s role in fruit
ripening
Sarah Minnery
~a tribute to summer~
….& locally grown seasonal
fruit
Outline
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FRUIT defined
RIPE FRUIT defined
ETHYLENE, the plant hormone
ETHYLENE & RIPENING of FRUIT,on
tissue level and molecular aspects
• CURRENT APPLICATIONS
Fruit defined..
• fruit is a mature ovary of the flower
• the wall of the ovary in the fruit is known as
the pericarp, becomes differenetiated into
– 1.outer exocarp
– 2.middle mesocarp
– 3.inner endocarp
• dlb fertilization is the trigger that evokes
endosperm development and embryogenesis
fruit defined..
• AFTER FERTILIZATION………
• transforming of ovule into seed
• the ovary increases in size and undergoes a
variety of morphological, anatomical and
biochemical changes leading to formation
of fruit with enclosed seeds
ripe fruit
• as a process, the term ‘fruit ripening’ is
misleading
• ripening is the final stage of fruit
development
• changes in biochemical pathway that are
studied;
– respiration, ethylene output, cartenoid
synthesis, chlorophyll degradation, production
of cell wall hydrolases and softening process
ripe fruit
• ripening is a differentiating process
– fruit have an increase in protein content
– fruit retain the capacity to synthesize proteins &
RNA
– inhibitors of protein & RNA synthesis prevent
the process of ripening ( I will come back to
this later)
ethylene plays a active role in..
1. shoot and root growth and
differentiation (triple response)
2. dormancy
3.adventitious root formation.
4.stimulates leaf and fruit abscission.
ethylene plays a active role in..
5. flower induction.
6. stimulates flower opening.
7. induction of femaleness in dioecious
flowers.
8. flower and leaf senescence.
9. fruit ripening.
the discovery of ethylene
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ancient Egyptians
ancient Chinese
1864; the gas lamps
1901; Dimitry Neljubow
1917; Doubt
1934; Gane
1935; Crocker
the discovery of ethylene
biosynthesis and metabolism
• Produced in all higher plants
• produced from methionine in essentially all
tissues
• products of ethylene depend on type of
tissue, the plant species, and the stage of
developement
biosynthesis and metabolism
– 1. Methionine (MET) + enzyme AdoMet
synthetase = S-Adenosyl-methionine (AdoMet)
– 2. AdoMet + ACC syththase = 1Aminocyclopropane-1-carboxylic acid (ACC)
– 3. ACC + ACC oxidase = ethylene
signals to ethylene production
• ripening signals are a burst of ethylene
production
• a wound, picking fruit, infection of bacteria
or fungi all will initiate the production
responses to ethylene
• Ethylene production or exposure to exogenous
ethylene initiates different responses in
different fruit.
• There are two types of fruit
• Climateric and non-climateric
• Climateric fruit show a large increase in ethylene
production at the onset of ripening. After ripening
ethylene output reaches a peak and continues at a
high level through ripening
responses to ethylene
• climateric fruit also respond to exogenous ethylene and
causes the ethylene production to increase and advances
the respiratory climateric in the fruits
• examples of climateric fruit are banana’s, apples and
pears
• non-climateric fruit do not produce ethylene during
ripening process but respond to exogenous and also
causes respiratory rate to increase. It does not promote
natural ripening of these fruits.
• examples of non-climateric fruit are citrus and different
berries such as strawberries
ethylene transport
• Ethylene transport within the plant
– Ethylene is released by the tissues & diffuses in the gas
phase through intracellular spaces & outside the tissues
• Ethylene transport within the fruit
– In comparison to ACC synthase and ACC oxidase, less
is known about ethylene perception and signal
transduction, because of difficulties in isolating and
purifying ethylene receptors or ethylene binding
proteins
ethylene signals result in the
ripening of fruit
1.Chlorophyll is broken
down, new pigments
surface, red, yellow or
blue
2. Acids are broken down
fruit changes from sour to
neutral to sweet
the ripening of fruit cont’
3. Amylase degrades starch
to sugar, hence the mealy
quality to juiciness
4. The breakdown of pectin
between the fruit cells
unglues them so they can
slip past each other, hence
the softer fruit
the ripening of fruit cont’
5. Breakdown of large
organic molecules to a
variety of type and
quantity of small volatile
molecules that produce
the aroma and tastes we
associate with ripe fruit
fruit ripening at molecular level
• changes in mRNA subsets
– include new gene transcription in mature fruit,
– a decrease in other transcriptions with
advancing maturity of fruits
– disappearance of certain mRNA’s in
overripened fruits
• in some more detail………activities of
cellulases, PG and PME
fruit ripening at molecular level
• cellulases are enzymes normally
functioning in cell walls causing breakdown
of cellulose and hemicellulose
• PME and polygalacturonase (PG) causing
pectin degradation
• above mentioned have led to
characterization of genes
fruit ripening at molecular level
• psbA, transcription in the chromoplasts which is at
least 20 fold than the transcript level of other
photosynthetic genes in ripe fruit
• PSY-phytoene synthase, 1st enzyme in cartenoid
pathway
• PME-enzyme causes pectin deformation of the
middle lamella of plant cell walls
– activity of enzyme inc. 2-3 fold during ripening
• PG, protein accumulates in pericarp first and
accounts for 3-5% of soluble proteins
– 2000 fold inc. in mature ripe fruits
current research
• Use of 1-MCP as a tool to investigate
whether exogenous ethylene binds to
the receptor to induce the respiratory
rise and to affect ripening in strawberry
fruit
• Use of cyclohexamide as protein
inhibitor to test whether the ethylene
effects are the result of new protein
synthesis. Changes in ionic
conductivity and peroxidase activity in
ethylene treated strawberries were
measured as markers
conclusions in research
• Ethylene induced ionic leakage and
associated water loss and peroxidase
activity
• Results suggest that non-climateric
fruit may have different ethylene
receptors and/or ethylene receptors
may have different regulatory functions
current applications
• carbon
application
• increasing
shelf life of
fruit
• Ethylene
controlled
environments
Thank you
& I hope
you have a
juicy
summer