Characterization of sequence and structural homology as
well as of the immunological and functional properties of plant
transglutaminases in relation to phylogenetic distribution.
Self-incompatibility in fruit trees and its importance on
productivity. Role of extracellular transglutaminase in signalling
and/or as adhesion factor. Modification of pollen antigens induced
by climate change and its importance in pollen allergenicity and
cross-allergenicity. Studies on pollen phospholipase and
transglutaminase activities and their possible involvement on
allergenicity. Programmed cell death in petals: post-translational
modification of proteins catalyzed by transglutaminase,
localization and possible role of the enzyme. Biotic and abiotic
stresses: involvement of transglutaminase and phospholipase
activities. Transglutaminase as biotecnological tools to improve
the features of food products
TGases are a family of enzyme involved in different
physiological activities as consequences of different reactions on
protein substrates (transamidation, protein cross-linking,
deamidation, GTP hydrolysis, disulphide isomerase reaction);
although TGs carry out various biological functions that are
generally attributed to their protein-modifying activity, in some
instances their biological function is due to specialized
non-catalytic actions, such as scaffolding of the cytoskeleton to
maintain membrane integrity, cell adhesion and possibly signal
transduction.
TGases have been found also in higher plants suggesting a
widespread distribution. One of the plant form has been sequenced
for the first time in this laboratory and its roles are under
investigation in Arabidopsis knock-out plants. Among the
different forms those of chloroplasts have a stabilizing and
protective effects on photosystems whereas those of pollen (with a
localization in cell wall) are involved in the organization and
modification of cell wall as well as in the interaction with
extracellular matrix
Some of these forms are under investigation to check their
sequence and structural homology as well as their immunological and
functional properties. Some of previous data have been shown the
presence of enzyme also in unicellular green alga. Research are in
progress to verify the distribution of TGases also in other plant
organisms to evaluate the distribution in relation to phylogeny.
In style/stigma-pollen self incompatibility of fruit tree, the
role of extracellular TGase will be evaluated as molecular signal
and/or adhesion factor. The products of TGase catalysis will be
studied on: 1) proteins encoded by locus S, as ribonuclease, 2)
proteins involved in the incompatibility mechanisms as the
cytoskeleton, cell wall and extracellular proteins, 3) proteins
responsible of cellular adhesion.
The main objectives are: purification of pollen TGase and its
biochemical characterization; evaluate a possible role of TGase in
self-incompatibility response in fruit tree where the regulative
mechanisms of compatibility is strictly related to fruit production
having indeed strong agro-economical implications.
A streak of research concern the possible involvement of TGase
in the increase of allergy to pollen treated to stress factors
related to climate changes; this hypothesis is based on the
unequivocal increase of allergy due to climate changes and to the
general involvement of TG during stress but also in asthma disease.
The TGase mechanism of action seem related to the modification of
antigen located in the pollen cell wall or in the activation
phospholipase A2, a factor responsible of inflammation response
after the contact with pollen. About the research on the plant
programmed cell death (PCD), as this phenomena is not completely
understood (in particular at cellular compartments level), the
activity is addressed to clarify the involvement of TGase in PCD
phenomena. The corolla of Nicotiana tabacum will be the
model in which to study the presence and the activity of enzyme
during growth, senescence and cell death also in sub-cellular
fraction enriched in chloroplasts, cell walls, cytosol and
microsomes. Parallely also the effects of polyamines (substrates of
TG in the transamitading reaction) will be checked on the
senescence by evaluating the amount and the last of supply. Part of
the research concern applicative aspect in the horticultural
sectors by with the aim to slow the senescence process in the
cutted flowers by the use of molecules with a low impact on the
environment.
The study on biotic and abiotic stresses will be perform on
tobacco plant in which the biotic stress as the HR response due to
virus infection and the mechanical stress due to wound will be
studied. In both cases the TGase activity will be analysed and the
comparison of the two types of stress will allow to understand if
one or both stress could have an influence on TGase activity and
indeed if TGase could be involved in the molecular mechanisms of
response to stresses.
