Increasing ω-3 Desaturase Expression in Tomato Results in Altered Aroma Profile and Enhanced Resistance to Cold Stress    

Abstract

One of the drawbacks in improving the aroma properties of tomato (Solanum lycopersicum) fruit is the complexity of this organoleptic trait, with a great variety of volatiles contributing to determine specific quality features. It is well established that the oxylipins hexanal and (Z)-hex-3-enal, synthesized through the lipoxygenase pathway, are among the most important aroma compounds and impart in a correct proportion some of the unique fresh notes in tomato. Here, we confirm that all enzymes responsible for the synthesis of these C6 compounds are present and active in tomato fruit. Moreover, due to the low odor threshold of (Z)-hex-3-enal, small changes in the concentration of this compound could modify the properties of the tomato fruit aroma. To address this possibility, we have overexpressed the v-3 fatty acid desaturases FAD3 and FAD7 that catalyze the conversion of linoleic acid (18:2) to linolenic acid (18:3), the precursor of hexenals and its derived alcohols. Transgenic OE-FAD tomato plants exhibit altered fatty acid composition, with an increase in the 18:3/18:2 ratio in leaves and fruits. These changes provoke a clear variation in the C6 content that results in a significant alteration of the (Z)-hex-3-enal/hexanal ratio that is particularly important in ripe OE-FAD3FAD7 fruits. In addition to this effect on tomato volatile profile, OE-FAD tomato plants are more tolerant to chilling. However, the different behaviors of OE-FAD plants underscore the existence of separate fatty acid fluxes to ensure plant survival under adverse conditions.

Ectopic expression of peanut acyl carrier protein in tobacco alters fatty acid composition in the leaf and resistance to cold stress

“…Increased production of C18:3 accompanies cold acclimation in many plants (Graham and Patterson 1982), and a positive relationship exists between a higher degree of fatty acid desaturation and both cold and freezing tolerance (Steponkus et al 1993, Zhang et al 2010. Modifying the level of unsaturated fatty acids present in membrane lipids contributes to improved cold tolerance in cold-sensitive crops (Domínguez et al 2010). In the present study, production of C18:2 and C18:3 in OE-AhACP1 lines was higher than in the wild type, which, in turn, was significantly higher than in antisense lines (Table 1).…”

“…It could be speculated that the content of unsaturated fatty acids at the sn-1 and sn-2 positions of phosphatidylglycerol, which is a plant membrane lipid, could be improved in OE-AhACP1 lines and their cold tolerance could be meliorated. Because most trienoic acids are present in thylakoid membranes, where the photosynthetic machinery is found, variation in their degree of unsaturation at low temperatures could play an important role in maintaining the photosynthetic capacity of the plants (Domínguez et al 2010). Furthermore, OE-AhACP1 plants showed greater antioxidant activity Table 2.…”

Expression profile of gene encoding Kelch repeat containing F-box protein (PmF-box1) in relation to the production of green leaf volatiles

“…The content of linolenic acid is critical in influencing the fluidity and permeability of the membrane. Therefore, there is a maximum content of linolenic acid that the cell can bear so that it will not interfere with the cell function especially in photosynthetic cell (Domínguez et al 2010).…”

Metabolic engineering of aroma components in fruits

“…The overexpression of ω-3 fatty acid desaturases from Brassica napus and potato (BnFAD3 and StFAD7) produced an increase in linolenic/linoleic acid ratio in tomato leaves and fruits. In addition, the transgenic lines presented an increase of the (Z)-3-hexenal/hexanal ratio, and were more tolerant to chilling [65].…”