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  • 1
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In order to continuously supply horticultural products for long periods, it is essential to store them after harvest in low temperatures. However, many tropical and subtropical fruits and vegetables, such as citrus, are sensitive to chilling. In previous studies, the authors have shown that a short hot water rinsing treatment (at 62°C for 20 s) increased chilling tolerance in grapefruit. In order to gain more insight into the molecular mechanisms involved in heat-induced chilling tolerance, PCR cDNA subtraction analysis was performed which isolated four different PCR fragments whose expression was enhanced 24 h after the heat treatment, and that showed high sequence homology with various plant HSP18-I, HSP18-II, HSP22 and HSP70 genes. It was found that the short hot water treatment given at 62°C for 20 s, but not at lower temperatures of 20 or 53°C, increased the expression of the various HSP cDNAs in grapefruit peel tissue. However, when the fruits were kept at ambient temperatures, the increases in HSP mRNA levels following the hot water treatment were temporary and lasted only between 6 and 48 h. Similar temporary increases in the HSP mRNA levels were detected following exposure of the fruit to a hot air treatment at 40°C for 2 h. Nevertheless, when the fruits were treated with hot water but afterwards stored at chilling temperatures of 2°C, the mRNA levels of the various HSP18-I, HSP18-II, HSP22 and HSP70 cDNAs increased and remained high and stable during the entire 8-week cold-storage period, suggesting their possible involvement in heat-induced chilling-tolerance responses. The chilling treatment by itself increased the expression of the HSP18-I cDNA, but had no effect on the mRNA levels of any of the other HSP cDNAs. Exposure of fruit to other stresses, such as wounding, UV irradiation, anaerobic conditions and exposure to ethylene, had no effect on the expression of the various HSPs. Overall, the study explored the correlation between the expression and persistence of various HSP cDNAs in grapefruit peel tissue during cold storage, on the one hand, and the acquisition of chilling tolerance, on the other hand, and the results suggest that HSPs may play a general role in protecting plant cells under both high- and low-temperature stresses.
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  • 2
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Dehydrins (DHNs; late embryogenesis abundant D-11) are a family of plant proteins induced in response to environmental stresses such as water stress, salinity and freezing or which occur during the late stages of embryogenesis. Previously, it was reported that citrus contains a small gene family encoding a unique class of dehydrins that differs from most other plant dehydrins in various respects, such as having an unusual K-segment similar to that of gymnosperms. In the present study, we identified by cDNA differential display analysis a ‘Navel’ orange 202-bp polymerase chain reaction (PCR) fragment, which encoded the typical plant angiosperm-type K-segment consensus sequence, and of which the expression was down-regulated by exposure to low oxygen levels. The full-length cDNA sequence of the orange DHN, designated csDHN (for Citrus sinensis DHN), was further isolated by 5′-and 3′-RACE; it had a total length of 933 bp and encoded a predicted polypeptide of 235 amino acids. In addition, the same 202-bp ‘Navel’ dehydrin PCR fragment was used to screen a ‘Star Ruby’ grapefruit flavedo cDNA library, and its full-length grapefruit homologue, designated cpDHN (for C. paradisi DHN) was isolated and found to have a total length of 1024 bp and to encode a predicted polypeptide of 234 amino acids. The defined orange and grapefruit DHN proteins were completely identical in the 196 amino acids of their N-terminus but differed in their C-terminus region. Overall, the csDHN and cpDHN proteins share 84% identity and contain the conserved dehydrin serine cluster (S-segment) and a putative nuclear localization signal, but csDHN has one conserved dehydrin K-segment consensus sequence, whereas cpDHN contains two dehydrin K-segments. Both csDHN and cpDHN represent single copy genes, in ‘Navel’ orange and ‘Star Ruby’ grapefruit genomes, respectively. We found that the cpDHN gene was consistently expressed in the fruit peel tissue at harvest, but that its message levels dramatically decreased during storage at either ambient or low temperatures. However, a pre-storage hot water treatment, given to enhance fruit-chilling tolerance, increased cpDHN mRNA levels during the first 3 weeks of cold storage at 2°C, and enabled the message levels to be retained for up to a further 8 weeks of cold storage at 2°C. The hot water treatment by itself had no inductive effect on cpDHN gene expression when the fruits were held at non-chilling temperatures. Other stresses applied to the fruit, such as wounding, UV irradiation, water stress, low oxygen and exposure to the stress hormone ethylene decreased DHN mRNA levels, whereas abscisic acid had no effect at all.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 100 (1997), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Tomato fruits are sensitive to low temperature and develop chilling injury, while at nonchilling temperatures they ripen rapidly. Previously, a hot-air treatment was found to reduce the sensitivity of the fruit to low temperatures. In the present study hot air was compared to hot water and their effects on reducing chilling injury and fungal decay were investigated. Tomatoes (Lycopersicon esculentum cv. Daniella) at the breaker stage were subjected to hot air, 48 h at 38°C, or various hot water dips, 30 min at 40°C or 2 min at 46, 48 or 50°C, before holding at 2°C. The unheated tomatoes developed chilling injury and fungal infections at 2°C, but not at 12°C. All the heat treatments reduced chilling injury and decay in tomatoes held for 3 weeks at 2°C. The outer pericarp tissue of heated tomatoes had higher phospholipid and lower sterol contents than unheated tomatoes. Heated tomatoes also had less saturated fatty acids than unheated tomatoes held at 2°C, but not at 12°C. Scanning electron micrograph observations showed that all the fruits had microcracks in their surface, but the unheated chilled tomatoes had also fungal growth in the cracks, while those of the heated tomato fruit did not. In the areas of chilling injury collapsed cells were present under the peel and could also support pathogen development. It is suggested that the heat treatment institutes a response to high temperature stress in the fruit tissue that leads to strengthened membranes. This prevents the loss of function and cell collapse which was found in the chilling-injured areas of affected fruit.
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  • 4
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Citrus fruits are sensitive to low temperatures and this often results in the development of chilling injuries during postharvest storage. In order to gain more insight into the molecular mechanisms involved in the acquisition of fruit chilling tolerance, we initiated a grapefruit (Citrus paradisi, cv. Marsh Seedless) flavedo cDNA sequencing project and used it to identify a cDNA similar to other Poncirus trifoliata and Citrus unshiu dehydrin genes reported to be responsive to low temperatures. The grapefruit dehydrin cDNA, designated cor15, encodes a predicted polypeptide of 15.1 kDa, that is almost completely identical with other reported citrus dehydrin proteins, except that it contains two large amino acid repeats, whereas P. trifoliata COR11 has only one such repeat and P. trifoliata COR19 and C. unshiu COR19 have three repeats. Together, the various grapefruit, P. trifoliata and C. unshiu dehydrins form a closely related and unique dehydrin gene family that differs from most other plant dehydrins in having an unusual K-segment similar to that of gymnosperms and in having a serine cluster (S-segment) at an unusual position at the carboxy-terminus. The grapefruit cor15 gene is consistently expressed in the fruit peel tissue at harvest, but its message levels dramatically decrease during storage at 2°C. However, a pre-storage hot water treatment, which enhances fruit chilling tolerance, elicited retention of the constant level of cor15 gene expression during cold storage and eliminated its decline. The hot water treatment had no inductive effect on cor15 gene expression when the fruit were held at non-chilling temperatures. The effects of other stresses, such as exposure to ethylene, UV irradiation and wounding, on cor15 gene expression, were temporary and persisted for 1-2 days after the treatments.
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  • 5
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A new postharvest hot water brushing (HWB) treatment, which sprays hot water on fruit as they move along a belt of brush-rollers, induced resistance against green mould decay caused by Penicillium digitatum (Pers. Fr.) Sacc in ‘Star Ruby’ grapefruit. The HWB treatment (62°C for 20 s) was most effective in inducing disease resistance when the fruit were inoculated after 1 and 3 days, but was less effective when the fruit were inoculated on the same day or 7 days later. The HWB treatment induced the accumulation of a 105-kDa protein that cross-reacted with an antibody raised against a bovine heat shock protein 70 (HSP70) and 18- and 21-kDa proteins that cross-reacted with pea HSP18 and HSP21 antibodies. The accumulation of a grapefruit 17-kDa protein that cross-reacted with a pea HSP17 antibody was not affected by the HWB treatment. HWB also induced the accumulation of 21-, 22- and 25-kDa proteins that cross-reacted with citrus and tobacco chitinase antibodies and 38-, 42- and 43-kDa proteins that cross-reacted with citrus and tobacco β-1,3-glucanase antibodies. The induction of the 105-, 18- and 21-kDa HSPs by the HWB treatment indicates that it was sufficient to provide a heat stress and, thus, was able to induce biochemical changes in the fruit peel tissue. Nevertheless, the accumulation of these HSPs was probably not related to the induction of fruit resistance against P. digitatum, since their accumulation could not be induced neither by direct inoculation with the pathogen nor following exposure to other treatments, such as UV irradiation, which also induce disease resistance. On the other hand, the increases in the accumulation of the 21-, 22- and 25-kDa chitinase proteins and of the 38- and 43-kDa β-1,3-glucanases proteins, which were observed 1 and 3 days after the HWB treatment when the fruit appeared to be more resistant to P. digitatum, may be part of the complex fruit disease resistance mechanisms induced by the heat treatment.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 119 (2003), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Peach fruit (Prunus persica cv. Hermosa) were allowed to ripen immediately after harvest or after 30 days of 0°C storage. The fruits lost 75–80% of their firmness after 5 days at 20°C. During ripening after harvest there was a loss of both uronic acid and methyl groups from the cell wall. Cell wall labelling with JIM 7, a monoclonal antibody which recognized pectins with a high degree of methylation, was lower in ripe fruits than in freshly harvested fruits. However, ripe fruit cell walls did not cross-react with JIM 5, which recognizes pectins with low methylation. During storage, de-methylation occurred and in fruit ripened after storage there was little further change in pectin methylation or pectin content in the cell walls. The labelling of stored or stored plus ripened cell walls with JIM 7 was similar, but the cell walls of fruit ripened after storage showed some low cross-reactivity with JIM 5. The in vitro activity and mRNA abundance of pectin esterase (EC 3.1.1.11) was not correlated with the amount of de-esterification as measured chemically or by immuno-labelling in the cell walls. Eighty percent of the fruits which ripened after storage developed a woolly texture. It is suggested that woolliness is due to de-esterification of pectins, not accompanied by depolymerization, which leads to the formation of a gel-like structure in the cell wall.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 78 (1990), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Apples (Malus domestica Borkh.) were heated for 4 days at 38°C immediately after harvest and then placed at 20°C for 7–10 days. Protein synthesis, ethylene production and fruit softening were reversibly inhibited by the heat treatment. Fruit respiration, membrane permeability and chlorophyll degradation in the fruit peel were enhanced during the treatment. The heat-treated apples ripened normally but more slowly than untreated apple We hypothesize that heat treatment differentially affects processes which normally increase simultaneously during fruit ripening, by inhibiting those processes which require tie novo protein synthesis and enhancing those that do not.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 53 (1981), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of temperature on ribulose bisphosphate carboxylase activity were studied in two tomato (Lycopersicon esculentum Mill.) cultivars which differed in sensitivity to high temperatures. The heat tolerant cultivar, Saladette, had a smaller reduction in photosynthesis and a smaller increase in mesophyll resistance then the sensitive cultivar Roma VF, after 24 h at 35 to 40°C. One hour in vitro treatments at 50°C decreased the activity of ribulose bisphosphate carboxylase extracted from Roma VF by 75%, while Saladette was not affected. Heat stress to the entire plant caused greater inhibition of ribulose bisphosphate carboxylase in the heat sensitive cultivar. Ribulose bisphosphate carboxylase activity in both cultivars decreased with heat treatment but recovered under normal temperatures. Ribulose bisphosphate oxygenase activity decreased similarly in both cultivars under 37/18°C day/night temperatures, which resulted in an apparent change in the relative carboxylase/oxygenase activity of the two cultivars. Carbonic anhydrase activity was slightly greater in Saladette than in Roma VF but no significant decrease in activity was observed in plants exposed to high temperatures.
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  • 9
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 103 (1998), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Environmental stresses dramatically affect plant survival and productivity. Because plants are immobile, presumably different strategies are required for protection against transient stresses. Under stress, plants synthesize specific proteins, and their accumulation has a role in protecting the tissue from possible damage. An increasing number of studies show the existence of cross-tolerance in plants: Exposure of tissue to moderate stress conditions often induces resistance to other stresses. Many varied mechanisms explaining the phenomenon of cross-tolerance have been proposed, and they often, but not always, suggest that specific proteins are induced by one kind of stress and are involved in the protection against other kinds. Although various cross-protections have been demonstrated in a number of plants, a common mechanism has not been found. This review discusses heat-shock proteins and their possible roles in protecting the plant under heat and other stresses.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Planta 140 (1978), S. 245-249 
    ISSN: 1432-2048
    Keywords: Action spctrum ; Ion uptake ; Malate ; Starch ; Stomata ; Vicia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of broad band green, blue and red light on stomatal opening of Vicia faba L. (broad bean) leaves was examined. In air, blue light caused greater stomatal opening than red light. In air with green light stomata were only slightly opened. In a nitrogen atmosphere red light caused greater opening than blue light, and green light caused only slight opening. Opening in air or nitrogen atmosphere in red or blue light was inhibited by the uncoupler CCCP, while the photosynthetic inhibitor DCMU inhibited opening in air but not in nitrogen atmosphere. We concluded that more than one light activated metabolic pathway can supply the energy needed to effect stomatal opening and that different pathways are operative under different conditions.
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