No abstract

The effect of ripening stage and water regimen on oleate desaturase gene expression levels in the fruit of different olive ( Olea europaea L.) varieties was investigated to elucidate the contribution of each to the linoleic acid content in virgin olive oil. To this end, fatty acid analysis and quantitative real time PCR were performed using distinct olive tissues and different developmental stages from the Picual and Arbequina cultivars. The results showed that the olive FAD2-1, FAD2-2, and FAD6 genes were spatial and temporally regulated. In addition, the data indicated that FAD2-2 seems to be the main gene responsible for the linoleic acid content in the olive fruit mesocarp tissue. This conclusion was also confirmed when the study was extended to Hojiblanca, Picudo, and Manzanilla varieties. With regard to the water regimen, unlike the Picual cultivar, a small increase of linoleic acid was observed in the Arbequina variety cultivated with irrigation, which correlated well with the increase detected for the FAD2-2 gene expression level. All of these data strongly suggest that FAD2-2 is the main gene that determines the linoleic acid content in the virgin olive oil.

Unsaturated fatty acids play an essential role in the biophysical characteristics of cell membranes and determine the proper function of membrane-attached proteins. Thus, the ability of cells to alter the degree of unsaturation in their membranes is an important factor in cellular acclimatization to environmental conditions. Many eukaryotic organisms can synthesize dienoic fatty acids, but Saccharomyces cerevisiae can introduce only a single double bond at the ⌬ 9 position. We expressed two sunflower (Helianthus annuus) oleate ⌬ 12 desaturases encoded by FAD2-1 and FAD2-3 in yeast cells of the wild-type W303-1A strain (trp1) and analyzed their effects on growth and stress tolerance. Production of the heterologous desaturases increased the content of dienoic fatty acids, especially 18:2⌬ 9,12 , the unsaturation index, and the fluidity of the yeast membrane. The total fatty acid content remained constant, and the level of monounsaturated fatty acids decreased. Growth at 15°C was reduced in the FAD2 strains, probably due to tryptophan auxotrophy, since the trp1 (TRP1) transformants that produced the sunflower desaturases grew as well as the control strain did. Our results suggest that changes in the fluidity of the lipid bilayer affect tryptophan uptake and/or the correct targeting of tryptophan transporters. The expression of the sunflower desaturases, in either Trp ؉ or Trp ؊ strains, increased NaCl tolerance. Production of dienoic fatty acids increased the tolerance to freezing of wild-type cells preincubated at 30°C or 15°C. Thus, membrane fluidity is an essential determinant of stress resistance in S. cerevisiae, and engineering of membrane lipids has the potential to be a useful tool of increasing the tolerance to freezing in industrial strains.Tolerance to freezing is an essential trait influencing the viability and leavening capacity of baker's yeast in frozen dough (4, 42). The so-called frozen-dough technology has been widely accepted by consumers and bakers due to several advantages, which include supplying oven-fresh bakery products and improving labor conditions. However, no appropriate industrial strain with a high tolerance to freezing is available, and it is unlikely that the classical breeding program could significantly improve this trait. Freezing is a complex and multifaceted stress, in which different stressors and stress responses appear to play important roles. Cells exposed to subzero temperatures are injured by the formation of ice crystals and crystal growth during frozen storage (33). At a slow freezing rate, cells are exposed to hyperosmotic solutions and equilibrate by movement of water across the membranes (65). Finally, during the thawing process, cells can suffer biochemical damage by oxidative stress (16). It is not surprising, therefore, that tolerance to freezing involves several mechanisms working in concert.Biological membranes are the first barrier that separates cells from their environment and are a primary target for damage during environmental stress. Sudden changes in envi...

Olive breeding programmes are focused on selecting for traits as short juvenile period, plant architecture suited for mechanical harvest, or oil characteristics, including fatty acid composition, phenolic, and volatile compounds to suit new markets. Understanding the molecular basis of these characteristics and improving the efficiency of such breeding programmes require the development of genomic information and tools. However, despite its economic relevance, genomic information on olive or closely related species is still scarce. We have applied Sanger and 454 pyrosequencing technologies to generate close to 2 million reads from 12 cDNA libraries obtained from the Picual, Arbequina, and Lechin de Sevilla cultivars and seedlings from a segregating progeny of a Picual × Arbequina cross. The libraries include fruit mesocarp and seeds at three relevant developmental stages, young stems and leaves, active juvenile and adult buds as well as dormant buds, and juvenile and adult roots. The reads were assembled by library or tissue and then assembled together into 81 020 unigenes with an average size of 496 bases. Here, we report their assembly and their functional annotation.

Plastidial ω-3 desaturase FAD7 is a major contributor to trienoic fatty acid biosynthesis in the leaves of Arabidopsis plants. However, the precise contribution of the other plastidial ω-3 desaturase, FAD8, is poorly understood. Fatty acid and lipid analysis of several ω-3 desaturase mutants, including two insertion lines of AtFAD7 and AtFAD8, showed that FAD8 partially compensated the disruption of the AtFAD7 gene at 22 °C, indicating that FAD8 was active at this growth temperature, contrasting to previous observations that circumscribed the FAD8 activity at low temperatures. Our data revealed that FAD8 had a higher selectivity for 18:2 acyl-lipid substrates and a higher preference for lipids other than galactolipids, particularly phosphatidylglycerol, at any of the temperatures studied. Differences in the mechanism controlling AtFAD7 and AtFAD8 gene expression at different temperatures were also detected. Confocal microscopy and biochemical analysis of FAD8-YFP over-expressing lines confirmed the chloroplast envelope localization of FAD8. Co-localization experiments suggested that FAD8 and FAD7 might be located in close vicinity in the envelope membrane. FAD8-YFP over-expressing lines showed a specific increase in 18:3 fatty acids at 22 °C. Together, these results indicate that the function of both plastidial ω-3 desaturases is coordinated in a non-redundant manner.