1,721,007 research outputs found
Osmotin induces cold protection in olive trees by affecting programmed cell death and cytoskeleton organization
No full textOsmotin is a pathogenesis-related protein exhibiting cryoprotective functions. Our aim was to understand whether it is involved in the cold acclimation of the olive tree (Olea europaea L.), a frost-sensitive species lacking dormancy. We exposed olive trees expressing tobacco osmotin gene under the 35S promoter (35S:osm) [in the same manner as wild type (wt) plants] to cold shocks in the presence/absence of cold acclimation, and monitored changes in programmed cell death (PCD), cytoskeleton, and calcium ([Ca2+](c)) signalling. In the wt, osmotin was immunolocalized only in cold-acclimated plants, and in the tissues showing PCD. In the 35S:osm clones, the protein was detected also in the non-acclimated plants, and always in the tissues exhibiting PCD. In the non-acclimated wt protoplasts exposed to cold shock, a transient decrease in phallotoxin signal suggests a temporary disassembly of F-actin, a transient increase occurred instead in 35S:osm protoplasts exposed to the same shock. Transient increases in [Ca2+](c) were observed only in the wt protoplasts. However, when F-actin was depolymerized by cytochalasin or latrunculin, and microtubules by colchicine, increase in [Ca2+](c) also occurred in the 35S:osm protoplasts. Successive cold shocks caused transient rises in [Ca2+](c) and transient decreases in the phallotoxin signal in wt protoplasts. No change occurred in [Ca2+](c) occurred in the 35S:osm protoplasts. The phallotoxin signal transiently increased at the first shock, but did not change after the subsequent shocks, and an overall signal reduction occurred with shock repetition. Following acclimation, no cold shock-induced change in [Ca2+](c) levels and F-actin signal occurred either in wt or 35S:osm protoplasts. The results show that osmotin is positively involved in the acclimation-related PCD, in blocking the cold-induced calcium signalling, and in affecting cytoskeleton in response to cold stimuli
In vitro plant regeneration from callus of shoot apices in apple shoot culture
No full textA new reliable protocol for the induction of adventitious shoot formation and plant regeneration from apple callus has been developed. High regeneration frequency was obtained with this method in four different genotypes (Jork9, M26, Gala and McIntosh) and callus maintained regeneration ability for several months. The procedure consists of inducing vegetative shoot apices, excised from in vitro shoots, for 20 days in darkness on an MS medium without glycine, supplied with 17.8 μM BA, 2.7 μM NAA and 250 mg l−1 cefotaxime. The explants are then transferred to a fresh auxin-free medium and given light. Histological studies revealed that all the regenerated shoots originated from callus. Regenerated shoots were multiplied, rooted and successfully established in soil
The protein of rolB gene enhances shoot formation in tobacco leaf explants and thin cell layers from plants in different physiological stages
No full textThe objective was to determine whether the protein of rolB affects shoot formation and whether this potential relationship depends on the developmental stages of the plant and/or on the culture conditions. Thin cell layers (TCL) and leaf explants were excised from tobacco plants in the vegetative and flowering stages and cultured under various hormonal conditions. In TCLs of vegetative-stage plants, the expression of rolB enhanced the formation of the shoot buds under hormone-free conditions and with specific concentrations of auxin and/or cytokinin, Histological examination showed that the induction of the shoot meristemoids was particularly enhanced by rolB protein and that meristemoid growth was accelerated. In leaf explants from vegetative-stage plants, the expression of rolB increased the formation of shoot buds in the presence of 1 mu M IAA plus 1 or 10 mu M cytokinin, With BA alone, at a 0,1 mu M concentration, shoot formation occurred in the transgenic explants only, whereas with concentrations ranging from 0.5 to in mu M, it was higher in these explants than in controls. RolB protein enhanced the formation of shoot buds in TCLs from flowering plants under all hormonal conditions. In the presence of 1 mu M IAA and kinetin, the protein also increased the flowering response. In leaf explants from flowering plants, the expression of rolB increased the number of shoot buds in the presence of 1 mu M IAA with 10 mu M BA, In conclusion, rolB protein promotes shoot formation; it seems to have a positive interaction with cytokinin and an effect on the induction of the meristematic condition
Unsaturated lipids change in olive tree drupe and seed during fruit development and in response to cold-stress and acclimation
Full text linkThe olive tree is a plant of economic value for the oil of its drupe. It is a cultigen complex composed of genotypes with differences in cold-hardiness. About 90% of the oil is stored in oil bodies (OBs) in the drupe during the oleogenic phase. Phenols and lipids contribute to oil quality, but the unsaturated fatty acid (FA) fraction is emerging as the most important for quality, because of the very high content in oleic acid, the presence of ω6-linoleic acid and ω3-linolenic acid, and the very low saturated FA content. Another 10% of oil is produced by the seed. Differences in unsaturated FA-enriched lipids exist among seed coat, endosperm, and embryo. Olive oil quality is also affected by the environmental conditions during fruit growth and genotype peculiarities. Production of linoleic and α-linolenic acids, fruit growth, fruit and leaf responses to low temperatures, including cuticle formation, and cold-acclimation are related processes. The levels of unsaturated FAs are changed by FA-desaturase (FAD) activities, involving the functioning of chloroplasts and endoplasmic reticulum. Cold induces lipid changes during drupe and seed development, affecting FADs, but its effect is related to the genotype capability to acclimate to the cold
Low-temperature sensing in olive tree: calcium signalling and cold acclimation
No full textOlive tree is a warm-temperature evergreen tree with low tolerance to frost, although cultivars which differ in terms of coldacclimation have been empirically selected. In herbaceous species, free cytosolic calcium ([Ca2+]c) is involved in coldacclimation. The objective of this study was to measure [Ca2+]csignalling in the olive tree during coldacclimation and to assess the possibility of using [Ca2+]c as an early genotype-selection marker of cold susceptibility. To this end, non-cold-acclimated and cold-acclimated leaf protoplasts of cultivars differing in terms of cold susceptibility were analysed. Cold shocks of various amplitude applied to non-cold-acclimated protoplasts caused consistent and transient increases in [Ca2+]c. A decrease of 0.05 °C/s (i.e. ΔT/dt=2.5 °C/50 s) was the threshold cooling rate at which a significant increase in [Ca2+]c could still be observed. When the protoplasts were incubated with either 8-(N,N-di-methylamino)octyl 3,4,5-trimethoxy-benzoate (TMB-8; organelle Ca2+ channel blocker) or Gd3+ (plasma membrane Ca2+ channel blocker), applying the threshold cooling rate, the increase in [Ca2+]c was partially inhibited, suggesting that both an intracellular release of Ca2+ and an influx through the plasma membrane are involved. When applying repeated cold shocks, the transient increases in [Ca2+]c were reduced only when using a non-severe ΔT/dt. In protoplasts subjected to standard acclimation, the increases in [Ca2+]c were further reduced, or inhibited, depending on the cold susceptibility of the cultivar, suggesting that the Ca2+ response is involved in a long-term adaptation to cold
Cold perception and gene expression differ in Olea europaea seed coat and embryo during drupe cold acclimation
No full textFAD2 and FAD7 desaturases are involved in cold acclimation of olive (Olea europaea) mesocarp. There is no research information available on cold acclimation of seeds during mesocarp cold acclimation or on differences in the cold response of the seed coat and embryo. How FAD2 and FAD7 affect seed coat and embryo cold responses is unknown. Osmotin positively affects cold acclimation in olive tree vegetative organs, but its role in the seeds requires investigation. OeFAD2.1, OeFAD2.2, OeFAD7 and Oeosmotin were investigated before and after mesocarp acclimation by transcriptomic, lipidomic and immunolabelling analyses, and cytosolic calcium concentration ([Ca2+]cyt) signalling, F-actin changes and seed development were investigated by epifluorescence/histological analyses. Transient [Ca2+]cyt rises and F-actin disassembly were found in cold-shocked protoplasts from the seed coat, but not from the embryo. The thickness of the outer endosperm cuticle increased during drupe exposure to lowering of temperature, whereas the embryo protoderm always lacked cuticle. OeFAD2 transcription increased in both the embryo and seed coat in the cold-acclimated drupe, but linoleic acid (i.e. the product of FAD2 activity) increased solely in the seed coat. Osmotin was immunodetected in the seed coat and endosperm of the cold-acclimated drupe, and not in the embryo. The results show cold responsiveness in the seed coat and cold tolerance in the embryo. We propose a role for the seed coat in maintaining embryo cold tolerance by increasing endosperm cutinization through FAD2 and osmotin activities
FAD8, lip and osmotin are cold-acclimation genes in Olea europaea L.
No full textOlive tree is an evergreen species of economic value lacking winter dormancy and showing low tolerance to
frost. This low tolerance limits its cultivation in cold regions, where, by contrast, oil quality is improved by
an enrichment in unsaturated fatty acids, i.e., linoleic (C18:2) and linolenic (C18:3) acids, produced by the
activity of specific fatty acid desaturases (FADs). Cold-resistant genotypes have been empirically selected
from centuries however the genetic network controlling cold-tolerance in olive tree is still unknown.
Transient changes in cytosolic calcium are involved in sensing the cold stress and in activating cold
acclimation in numerous plants, including olive tree (1-2). A role for the PR-5 protein Osmotin (OeOSM) in
olive tree cold acclimation has been suggested, possibly as transfer protein to the cell wall of cutinsomes,
containing unsaturated fatty acid-derived compounds (3, 4). The expression of genes coding for specific
FADs, i.e. OeFAD2.2 and OeFAD7, necessary for C18:2 and C18:3 production, respectively, has been
demonstrated to be positively related to olive tree drupe cold-response. However, the expression of both
genes normally occurs during oil biogenesis, and increases under cold-stress independently of the
acclimation capabilities of the genotypes, suggesting that these genes are unrelated with cold acclimation (2).
By contrast, in Arabidopsis thaliana and other plants, FAD8, isoform of FAD7, is specifically activated by
cold (5). Moreover, FAD8 expression in maize is activated concomitantly with the beta-Zip LIP transcription
factor mlip19 (6), and members of LIP19-family are activated by calcium transients (7). The research aim
was to identify transcripts of an OeLIP gene in leaves and drupes of two genotypes, one incapable and the
other capable of cold acclimation, by cold-stresses applied before, during and after the possible
natural/artificial acquisition of cold acclimation, investigating, in parallel, the changes in OeOSM and
OeFAD8 expression, the immuno-localization of OeOSM, and by detecting the levels of C18:3-compounds
deriving by OeFAD8 activity. Preliminarly, leaves and drupes belonging to cv. Moraiolo and cv. Canino
were exposed to cold shocks of different duration and intensity at the same developmental stages, and the
cold response evaluated in their protoplasts in terms of presence/absence of cytosolic calcium transients, for
determining their differences in cold acclimation under all cold conditions. Both genotypes were cold
sensitive at the beginning of the oil biogenesis in the drupe (WAF 10), however Canino was able to acquire
artificial acclimation at this WAF. Only cv. Moraiolo showed calcium rises, i.e. remained cold-sensitive at
the end of oil biogenesis (WAF 19) in leaves and drupes, and continued to be sensitive even in full winter
(WAF 26), showing its total inability to cold acclimate, differently from the other genotype.
An OeLIP gene was isolated and characterized, and its changes monitored by q-PCR in both leaves and
drupes under the same cold-shocks applied for monitoring cytosolic calcium changes. OeLIP was activated
by cold-induced calcium signalling. Its expression increased with cold, but became stable only in Canino.
OeFAD8 transcription was also induced by calcium signalling, and changed in parallel with that of OeLIP.
The production of C18:3, and related compounds, by OeFAD8 activity, increased in Canino in concomitance
with acclimation. Also OeOSM was activated by calcium signalling, and its transcripts were high and stable
during acclimation acquisition and maintenance by Canino drupes and leaves. Moreover, both organs
showed increased cutinisation of the outer cell walls of epicarp and adaxial epidermis, respectively, with this
event strongly increasing in Canino, and positively coupling with an increased immunolocalization of
OeOSM in the cuticle. All together, results demonstrate that OeFAD8, OeLIP and OeOSM jointly control
cold-acclimation in Olea europaea drupes and leaves
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