1. ethylene, and it’s role in fruit ripening
Sarah Minnery

2. ~a tribute to summer~ ….& locally grown seasonal fruit

3. Outline FRUIT defined RIPE FRUIT defined ETHYLENE, the plant hormone
ETHYLENE & RIPENING of FRUIT,on tissue level and molecular aspects
CURRENT APPLICATIONS

4. 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

5. 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

6. 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

7. 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)

8. ethylene plays a active role in..
shoot and root growth and differentiation (triple response)
dormancy
adventitious root formation.
stimulates leaf and fruit abscission.

9. ethylene plays a active role in..
flower induction.
stimulates flower opening.
induction of femaleness in dioecious flowers.
flower and leaf senescence.
fruit ripening.

10. the discovery of ethylene
ancient Egyptians
ancient Chinese
1864; the gas lamps
1901; Dimitry Neljubow
1917; Doubt
1934; Gane
1935; Crocker

11. the discovery of ethylene

12. 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

13. biosynthesis and metabolism
1. Methionine (MET) + enzyme AdoMet synthetase = S-Adenosyl-methionine (Ado-Met)
2. AdoMet + ACC syththase = 1-Aminocyclopropane-1-carboxylic acid (ACC)
3. ACC + ACC oxidase = ethylene

14. 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

15. 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

16. 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

17. 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
Using biochemical methods

18. 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
Hydrolases to break down chemicals
amylases to accelerate hydrolysis of starch into sugar
pectinases to catalyze degradation of pectin

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. current applications carbon application increasing shelf life of fruit
Ethylene controlled environ-ments

27. Thank you & I hope you have a juicy summer