Vacuoles are membrane-bound organelles present in plant, fungal, and some protist and animal cells. There are three main types of vacuoles: storage vacuoles, contractile vacuoles involved in osmoregulation, and vacuoles involved in autophagy. Plant cell vacuoles occupy most of the cell volume and provide structural support and storage. Fungal vacuoles maintain a low pH through V-type ATPase pumps. During cell division, vacuoles are segregated into daughter cells through actin filament transport mediated by myosin motor proteins.

1. VACUOLE
Presented by: Arjama Dhar Roy
M.Sc. ; Life Sciences, 1st Semester, CUG; 2014.

2. §
Topics to be discussed:
•
What is Vacuole?
•
Where is it present?
•
How many types of them are there?
•
What are their functions?
•
Short discussion about their versatility in structure and function.
•
Fungal vacuoles have special ATPase system to maintain their Low PH.
•
The fate of vacuoles during cell division.

3. •
Where is it present?
Vacuoles are present in large significance in plant cells. Fungal
cells and some protists(Paramoecium sp.) and even animal
cells also content vacuoles which are small, numerous and
functionally less significant than plant cell vacuoles. Bacteria
•
What is vacuole?
Vacuoles are membrane bound enclosed compartments
which are rich in different types of organic and inorganic
Molecules including enzymes and pigments and other
metabolic products.

4. Ø
Because vacuoles are present inside a
cell and participate in cellular functions,
they are cell organelles and membrane
bound- tonoplast.
•
Basically there are three types of vacuoles:
ü
Storage vacuoles [nutrients and pigments and waste
product].
ü
Contractile vacuoles[osmotic regulation].
ü
Vacuoles involved in autophagy.

5. Ø
Functions:
•
Plant cells have large vacuoles. Occupying the central region
of the cell[approx. 80% of the cell volume].They provide
structural support, disposal of waste products, storage of
pigments and nutrients, help in growth. Also maintains
turgor pressure.
•
Animal cells contain numerous small vacuoles those
function in storage and transport: exocytosis and
endocytosis.
•

6. •
Exocytic Vesicle
-ü
They transport specific molecules[generally
Proteins or peptides or other molecules with specific
Export sequence. Transport happens from inside the
Cell to the outside.
•
ENDOCYTIC VESICLE:
ü
Transport of molecules from outside of the cell
to the inside. i) receptor mediated , ii)phagocytosis
iii) pinocytosis.

7. ü
Contractile vacuole:
a. Contractile vacuoles are present in Amoeba and
Chlmydomonus sp.
b. Contractile vacuoles are involved in transcytosis .
c. Osmotic regulation and waste products are
Transported from inside the
Cell to the outside.

8. Ø
Fungal vacuoles maintain High [H+] in them: V-
type ATPase
ü
Fungal vacuoles maintain high proton concentrations inside their lumen.
ü
For maintaining low PH vacuoles of
fungal cells have specialized
ATPase[ V-type] to pump H+ ions
from cytosol to vacuolar lumen
against the expenditure of ATP. Low
PH is needed for the optimal
activation of enzymes.

9. •
V-type ATPase are also important for vesicular transport of proteins.
•
V-ATPase activity is maintained by i) assembly and disassembly of two
subunits[V0 and V1], ii)n the transcription and translational level and
•
iii) by chloride channels.
Ø
Chloride channel dependent regulation: Voltage gated Cl(-) channels are
present on tonoplast. They antiport the Cl(-) ions and dissipating the
proton gradient; ratio- 2:1.
•
V type ATPase translocates H+ ions from the cytosol to the vacuolar
lumen and a positive charge generated across the membrane limits the
activity of the pump. So Chloride ion pumps transport Cl(-) ions to the
lumen also!!

10. Ø
Autophagy mediated by certain vacuoles:
•
Autophagy involves transport of cellular organelles to the vacuoles and
their degradation- result of prolonged starvation.
•
Overlaps biosynthetic pathway-CVT[ cytoplasm to vacuole
targeting]..
•
Macroautophagy and microautophagy.
•
PMSF treated cells can`t digest cellular
Cargo – formation of intravacuolar
Vesicles[ autophagic bodies] .

11. Continuation……
•
Autophagy may be specific[ CVT pathway] or nonspecific.
•
Many proteins including CVT9, CVT3. TLG2P are necessary
for CVT pathway- mutation of any of these proteins leads to
accumulation of PrAPI.
•
Vac8 mutants are defective in autophagy.

12. Ø
Segregation of Vacuoles During Cell
Division:
•
During cell division cell organelles are not synthesized de novo
•
Dramatic translocation of vacuolar portion is observed during cell cycle in
yeast.
•
Actin mutants can`t `segregate vacuoles into daughter cells.
•
Myo2P, an unusual molecular motor protein is involved in translocation-
along the actin filaments.
•
Vacuolar inheritance depends upon localization of cytoskeletal proteins
towards tonoplast.

13. ü
In brief:
•
Vacuoles are membrane bound cell organelles.
•
They are important in cellular transport, maintenance of pH,
storage of substances, and induction of cell death during
starvation.[Other than apoptosis].
•
Segregation of them is dependent upon cellular cytoskeletal
movements[S. cerevisiae]

14. THANK YOU!