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Pollen wall proteins
1. Welcome to
Pollen Wall Proteins
By N.Sannigrahi, Associate Professor, Department of
Botany, Nistarini College, Purulia, 723101(W.B) India
2. POLLEN WALL PROTEINS
• Pollen walls-exine or intine along with other zones
are treasure of proteins mostly enzymatic in
nature.Cytochemical methods are used to examine the
distribution of acid phosphatases, esterase, amylases
and protease activity and proteins in the walls of
pollen grains and spores. In all aperturate grains,
activity concentrated in or around the aperturate
intine and this is over or near the potential site of the
emergence of the pollen tube. Protein concentrations
in the intine can be explored by many ways.
• The intine enzymes are readily leachable and their
function is connected with the early nutrition of the
pollen tube and the penetration of the stigma.
3. SITE OF LOCALIZATION OF POLLEN WALL PROTEIN
• 5 classes of proteins- monaperturate, monoporate,
polyporate, monocolpate and tricolpate and triporate
• On the basis of localization of wall proteins other
than enzymatic activity, representing 4 of the above
structural classes-
• In the superficial materials contributed by the tapetum
during the later stages of pollen maturation, the
tryphine or pollen kit
• The cavities within sexine or between the sexine and
nexine
• In association with the cellulose of intine
6. Location of Pollen Wall Proteins
• T.Singer & Petrovsky-Baranova(1961) were the first to
demonstrate the existence of proteins along with the
enzymes in certain layers of the pollen walls of Paeonia
and Amaryllis. Subsequently, Makienen & MacDonald
(1968) demonstrated the pollen enzymes and isozymes in
the flowering plants of angiosperms. Pollen proteins are
very important as far as structure & function is concerned.
It is distributed in three layers-
• Cellulosic intine-endintine at the aperture part in the form
of radially arranged tubules,
• Exine proteins in the cavities between baculae of the
tectate grains or in the surface of the depressions of the
intactate or subtactate grains
• Either in the tapetum or the pollen kit.
7. Main Enzymes cum Protein
• Esterase –predominant enzymes of the exine
• Acid phosphatases-Chief enzymes in intine, so, the two
proteins are marker enzymes
• Helianthus pollen contain both in exine & intine-an
exception
• Maltase, lipase, several phosphorylases and zymases not
been reported in pollen.
• The activity of some enzymes like alkaline phosphatase,
ATPase, DNA synthetase & β-1,3-gluconase are reported
to be very low or absent in pollen grains.
• Pollen slowly loses certain types of enzymatic activity
during storage but these can not account for the rapid loss
of viability.
8. FORMATION OF INTINE PROTEIN
• After the release of the monad grain from tetrad, the plasma
lemma, of pollen cytoplasm put out radially oriented tubules
with their protein addition into the developing intine.
• Subsequently, these tubules disconnect from plasmalemma and
are sealed off from the cell surface with the deposition of a
further layer of intine from tubules.
• In aperaturate grains, proteins are dispersed throughout the
intine while in aperturate grains intine proteins are mostly
condensed in the aperatural region.
• Exine proteins originate from the sporophytic tapetum tissue
and the proteins and lipids are free into the thecal cavity after
breaking down the tapetal cells. So, exine proteins are the
product of the tapetal cells , hence they are sporophytic in
origin.
9. CONCLUSION
• From the above observations, it has been found that several
acid hydrolyses are present in the pollen wall , specifically
associated with intine. Since all of the angiosperm and one
gymnosperm tested uniformly possess the wall enzymes, a
connection with the heterophytic mode of the nutrition of the
male gametophyte is suspected. The incorporation of the wall
enzymes is concluded before the end of the intine growth , and
so precedes pollen mitosis and final accumulation of reserves
in pollen cytoplasm.
• Thus, pollen grains, the 1st cell of the male gametophytes
caters a strong biological heritage as far as its protein and
enzymes chemistry is concerned.
10. HOPE, THE PLEASURE OF PROTEIN WALL IS A
TREASURE OF BIOLOGY TO YOU.
THANKS A LOT FOR YOUR MEANINGFUL COMPANY.
