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Microsomal polypeptides in sunflower (Helianthus annum). Comparison between normal type before and after cold-induction, and a high oleic acid mutant (1994)

Sarmiento, Cristina ; Mancha, Manuel ; Garcés, Rafael

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 91 (1994), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Differences in high-resolution two-dimensional gel electrophoresis patterns of micro-somal proteins from developing normal sunflower (Helianthus annuus L.) seeds before and after cold-induction, and also from normal and a high oleic sunflower mutant have been studied in order to detect the polypeptides associated with the microsomal Δl2-desaturase activity and its regulation by temperature. Proteins were obtained from developing seeds of two isogenic sunflower lines HA-89 (normal) and HA-OL9 (high oleic) which greatly differed in linoleic acid content and “in vitro” oleate desaturase activity. In the high oleic mutant, four polypeptides of about 32 kDa and two of 33 kDa were found to change in position, to the same extent, toward a lower isoelectric point in the high oleic mutant. Also, two polypeptides, of 32 and 49 kDa each, appeared in the mutant. Quantitative differences between cold-induced seeds (10°C, 24 h) and their non-induced controls were found. One polypeptide of 43 kDa decreased in the cold-treated seeds and two others, of 30 and 32 kDa each, increased markedly after cold induction. Some of these polypeptides could be related to oleate desatnrase activity or its regulation by temperature.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb00664.x

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Oxygen-independent temperature regulation of the microsomal oleate desaturase (FAD2) activity in developing sunflower (Helianthus annuus) seeds (2003)

Martínez-Rivas, José M. ; Sánchez-García, Alicia ; Sicardo, M. Dolores ; [et al.]

Oxford, UK : Munksgaard International Publishers

Physiologia plantarum 117 (2003), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The temperature and oxygen regulation of the microsomal oleate desaturase (FAD2, EC 1.3.1.35) activity has been studied in developing sunflower (Helianthus annuus L.) seeds. In plants cultivated in growth chambers, the linoleic acid content in the seed lipids increased along the 25/15°C (day/night) cycle, except during the first hours of the warm period, where it decreased significantly. In contrast, FAD2 activity decreased notably at the beginning of the warm period, showing a small and continuous increase during the rest of the cycle. The temperature effect on the linoleic acid content and the FAD2 activity was also investigated using peeled seeds and detached achenes subjected to temperature changes. In peeled seeds, a change of temperature from 10 to 30°C brought about a significant decrease of FAD2 activity. On the contrary, when the temperature shifted from 30 to 10°C, FAD2 activity only increased slightly. Unlike peeled seeds, detached achenes showed a fast and dramatic increase or decrease in the level of FAD2 activity in response to a temperature change from 30 to 10°C, or from 10 to 30°C, respectively. The in vivo and in vitro thermal properties of the FAD2 enzyme were also studied. Optimal temperature and heat-resistance profile showed similar patterns in both conditions. All these data support the hypothesis that temperature regulates FAD2 activity by two different and independent mechanisms: a direct effect, and an indirect effect affecting oxygen availability. Furthermore, these results suggest that the low thermal stability of the enzyme is the main factor responsible for the direct temperature effect on FAD2 activity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1034/j.1399-3054.2003.00039.x

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Temperature and oxygen regulation of oleate desaturation in developing sunflower (Helianthus annuus) seeds (2002)

García-Díaz, M. Teresa ; Martínez-Rivas, José M. ; Mancha, Manuel

Oxford, UK : Munksgaard International Publishers

Physiologia plantarum 114 (2002), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The effect of low (10°C) and high (30°C) temperature on in vivo oleate desaturation has been studied in developing sunflower (Helianthus annuus L.) seeds under conditions of different oxygen availability (capitulum, detached achenes or peeled seeds). In seeds remaining in the capitulum, only a part of the oleate newly synthesized at high temperature was desaturated to linoleate, whereas more oleate than that synthesized de novo was desaturated at low temperature. Achenes were only able to significantly desaturate oleate at low temperatures. In contrast, oleate desaturation was detected in peeled seeds incubated at low and high temperatures, showing the highest rate at 20°C. Hull removing dramatically increased the activity of the microsomal oleate desaturase (FAD2, EC 1.3.1.35) at all studied temperatures, although a long-term inactivation of the enzyme was observed at high temperatures. Low oxygen concentration (1–2%) obtained by respiration of peeled seeds incubated in sealed vials, brought about the inactivation of the enzyme. All these data suggest that temperature regulates oleate desaturation controlling the amount of oleate and the FAD2 activity. In addition, this enzyme seems to be also regulated by the availability of oxygen, which is affected inside the achene by its diffusion through the hull, and the competition with respiration, both factors being temperature-dependent.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1034/j.1399-3054.2002.1140103.x

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4

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Remodelling of triacylglycerols in microsomal preparations from developing castor bean (Ricinus communis L.) endosperm (1997)

Mancha, Manuel ; Stymne, Sten

Springer

Planta 203 (1997), S. 51-57

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ISSN: 1432-2048

Keywords: Key words: Microsome ; Oil seed ; Ricinoleic acid ; Ricinus ; Triacylglycerol

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract. Microsomal preparations from developing castor bean (Ricinus communis L.) endosperm catalyzed remodelling of in-situ-formed triacylglycerol (TAG) species. Castor bean microsomal membranes synthesized [14C]TAGs from either glycerol 3-phosphate and [14C]ricinoleoyl-CoA or [14C]glycerol 3-phosphate and ricinoleoyl-CoA. Upon repelleting and subsequent incubation of the microsomes a redistribution occurred of both the [14C]glycerol and [14C]ricinoleoyl moieties of the in-situ-synthesized [14C]TAGs. Radioactivity was transferred from TAG species with three (3HO-TAG) or two (2HO-TAG)ricinoleoyl groups into species with two or one (HO-TAG) ricinoleoyl groups. Mass analysis of the lipid and fatty acid movements in the membranes showed that a net synthesis of TAGs with no, one and two ricinoleoyl groups occurred at the expense of 3HO-TAG and polar lipids. Thus, the non-hydroxylated acyl groups from polar lipids were used in the remodelling of TAGs. In-vivo feeding of [14C]ricinoleic acid to slices of castor bean endosperm demonstrated the presence of two radioactive pools of TAGs one in the oil bodies, which was rich in [14C]3HO-TAG, and one associated with the microsomal membranes, which was dominated by radioactive 1HO-TAG and 2HO-TAG. The microsomal TAG pool was remodelled in vivo in a similar way as in the in-vitro experiments with microsomal membranes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004250050164

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Triacylglycerols are synthesised and utilized by transacylation reactions in microsomal preparations of developing safflower (Carthamus tinctorius L.) seeds (1997)

Stobart, Keith ; Mancha, Manuel ; Lenman, Marit ; [et al.]

Springer

Planta 203 (1997), S. 58-66

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ISSN: 1432-2048

Keywords: Key words:Carthamus (lipids) ; Lipid interconversion ; Microsome ; Oil seed ; Transacylation ; Triacylglycerol

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract. Microsomal membrane preparations from the immature cotyledons of safflower (Carthamus tinctorius) catalysed the interconversion of the neutral lipids, mono-, di-, and triacylglycerol. Membranes were incubated with neutral lipid substrates, 14C-labelled either in the acyl or glycerol moiety, and the incorporation of radioactivity into other complex lipids determined. It was clear that diacylglycerol gave rise to triacylglycerol and monoacylglycerol as well as phosphatidylcholine. Radioactivity from added [14C] triacylglycerol was to a small extent transferred to diacylglycerol whereas added [14C] monoacylglycerol was rapidly converted to diacylglycerols and triacylglycerols. The formation of triacylglycerol from diacylglycerol occurred in the absence of acyl-CoA and hence did not involve diacylglycerol acyltransferase (DAGAT) activity. Monoacylglycerol was not esterified by direct acylation from acyl-CoA. We propose that these reactions were catalyzed by a diacylglycerol: diacylglycerol transacylase which yielded triacylglycerol and monoacylglycerol, the reaction being freely reversible. The specific activity of the transacylase was some 25% of the diacylglycerol acyltransferase activity and, hence, during the net accumulation of oil, substantial newly formed triacylglycerol equilibrated with the diacylglycerol pool. In its turn the diacylglycerol rapidly interconverted with phosphatidylcholine, the major complex lipid substrate for Δ12 desaturation. Hence, the oleate from triacylglycerols entering phosphatidylcholine via this route could be further desaturated to linoleate. A model is presented which reconciles these observations with our current understanding of fatty acid desaturation in phosphatidylcholine and oil assembly in oleaceous seeds.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004250050165

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6

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Oleate desaturation and acyl turnover in sunflower (Helianthus annuus L.) seed lipids during rapid temperature adaptation (1998)

Sarmiento, Cristina ; Garcés, Rafael ; Mancha, Manuel

Springer

Planta 205 (1998), S. 595-600

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ISSN: 1432-2048

Keywords: Key words:Helianthus (seed) ; Microsome ; Oil body ; Oleate desaturase ; Temperature adaptation ; Triacylglycerol

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract. In-vivo experiments with developing sunflower (Helianthus annuus L.) seeds demonstrated that oleate desaturase activity was stimulated by low temperature (10 °C), repressed by high temperature (30 °C) and rapidly restored by returning the seeds to low temperature. Within time periods of 2–4 h, in which the de-novo fatty acid synthesis was negligible, the percentages of oleate (18:1) and linoleate (18:2) were modified in the seed lipids as a consequence of temperature adaptation. When the seeds were transferred to low temperature, the 18:2 content increased in all lipids from both microsomal membranes and oil bodies. After shifting to high temperature, the overall 18:2 content remained constant, but the 18:2 content decreased in diacylglycerols, phosphatidylcholine (PC) and other polar lipids of the two fractions and also in triacylglycerols (TAGs) of the microsomes but increased in TAGs of the oil bodies. The results indicate that the mechanism for the rapid adaptation of sunflower seeds to temperature changes involves (i) the synthesis or activation of oleate desaturase at low temperature and the reversible inhibition of this enzyme at high temperature and (ii) the exchange of 18:1 and 18:2 between TAGs and PC. Under both low and high temperature, 18:1 is transferred from reserve TAGs to PC and 18:2 is transferred from PC to reserve TAGs. At low temperature, 18:1 is desaturated to 18:2 thus allowing the enrichment of membrane lipids with 18:2, the excess being stored in reserve TAGs. At high temperature, however, and provided that oleate desaturase is repressed, the membrane lipids become enriched in 18:1 and the oil-body TAGs become enriched in 18:2.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004250050361

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7

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Sunflower mutant containing high levels of palmitic acid in high oleic background (1997)

Fernández-Martínez, José M. ; Mancha, Manuel ; Osorio, Jorge ; [et al.]

Springer

Euphytica 97 (1997), S. 113-116

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ISSN: 1573-5060

Keywords: Helianthus annuus ; fatty acids ; palmitic acid ; X-ray mutagenesis ; seed oil ; sunflower

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract A new sunflower mutant, CAS-12, was obtained, which has both high palmitic (≈30%) and high oleic acid contents, and also a substantial amount of palmitoleic acid (≈7%). The mutant was selected after X-ray irradiation of dry seeds of the inbred line BSD-2-423, which had normal palmitic (≈3%) and high oleic (≈88%) acid levels. The increase of palmitic and palmitoleic acids occurred at the expense of the oleic acid content, which decreased to around 55% in respect to the original line. Linoleic acid content is always under 5%. Palmitic and palmitoleic acid levels were similar to those of the high palmitic mutant CAS-5 obtained in a previous programme from a low oleic line isogenic to BSD-2-423 using a similar mutagenic treatment. In that previous programme we also selected three high stearic acid mutants using chemical mutagenic treatment on the same sunflower line (RDF-1-532). We attempted to obtain mutants in other lines but were unsuccessful. The isolation of similar mutants in isogenic parental lines illustrates the importance of the genetic background in the development of specific mutants with an altered seed oil fatty acid composition. The oil of this mutant will increase the range of potential uses of sunflower oil.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1003045726610

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