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Uploaded byNistarini College, Purulia (W.B) India
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Pollen wall proteins

The document discusses pollen wall proteins, emphasizing their enzymatic nature and significance for the nutrition and function of pollen tubes during fertilization. It details the distribution and localization of various proteins in different pollen structures and highlights the main enzymes such as esterases and acid phosphatases found within the pollen walls. The conclusions suggest a crucial role for wall enzymes in angiosperms and their connection to gametophyte nutrition and development.

Science◦
Welcome to Pollen Wall Proteins By N.Sannigrahi, Associate Professor, Department of Botany, Nistarini College, Purulia, 723101(W.B) India
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.
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
Different Pollen Morphology
POLLEN WALL PROTEINS
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.
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.
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.
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.
HOPE, THE PLEASURE OF PROTEIN WALL IS A TREASURE OF BIOLOGY TO YOU. THANKS A LOT FOR YOUR MEANINGFUL COMPANY.