Proceedings of the XLVI Italian
Society of Agricultural Genetics - SIGA Annual Congress
Giardini
Naxos, Italy - 18/21 September, 2002
ISBN 88-900622-3-1
Poster
Abstract - 4.01
WHEAT
THERMOTOLERANCE: FROM CELLULAR TO MOLECULAR ANALYSIS
CORRADI M.*,
GULLÌ M.*, DE VITA P.**,
PERROTTA C.*-***
*) Dipartimento
di Scienze Ambientali, Università di Parma
**) Istituto
Sperimentale per la Cerealicoltura Sez. Foggia
***) Dipartimento
di Scienze e Tecnologie Biologiche ed Ambientali, Università di Lecce
thermotolerance,
wheat, heat shock proteins
Plants
are exposed, more than animals, to various environmental stresses. One of the
more common is due to temperatures higher than the optimal requirement. In
these situations there are several kinds of response, acting from molecular to
physiological level: one of the prompter and common to every organism is the
transient synthesis of a particular set of proteins called heat-shock proteins
(HSPs) concomitant with blocking of normal protein synthesis. HSPs can be
classified into five groups on the basis of their molecular masses: HSP 100,
90, 70, 60 and low molecular weight HSPs (smHSPs), typically abundant in
vegetables. They are all molecular chaperones, involved in protection of the
other cellular proteins against damages deriving from exposure to high
temperature, so preventing protein aggregation and refolding or disaggregating
partially denatured ones.
Plants
can acclimate to high temperatures following an initial exposure to mild heat
stress, obtaining higher thermotolerance and surviving normally lethal
temperatures. The appearance of HSPs is strongly correlated to the development
of a condition called acquired thermotolerance. A second component of
thermotolerance is due to evolutionary thermal adaptation of species to their
habitat and it is named inherent thermotolerance.
Plants
show a high degree of variability in heat-shock response and these variations
are mostly due to genetic variability. Moreover wild plants rarely die as a
consequence of temperature fluctuation in their environments, whereas
cultivated plants, selected for yield potential and for being ecologically
ubiquitous, have a very reduced tolerance to heat stress.
In order
to elucidate the molecular mechanisms underlying the acclimation process we
evaluated genetic variation in cellular thermotolerance, both inherent and
acquired, of several genotypes of wheat (20 wild, 14 commercial and 13
obsolete) by cell membrane stability (CMS) and triphenyl tetrazolium chloride
(TTC) cell viability assays. From these analyses the wheat genotypes were
classified as tolerant or susceptible.
On the
basis of their inherent thermotolerance some cultivars among the more tolerant
and the more susceptible were chosen for expression analysis. RNAs were
purified from plants grown in the field under normal and heat stress conditions
and the expression of several HSPs was detected.
This
analysis will allow to correlate the results obtained with physiological tests
to the modification of gene expression in response to the conditions
experienced by plants in natural environments.