Improvement of Aroma in Transgenic Potato As a Consequence of Impairing Tuber Browning

Sensory analysis studies are critical in the development of quality enhanced crops, and may be an important component in the public acceptance of genetically modified foods. It has recently been established that odor preferences are shared between humans and mice, suggesting that odor exploration behavior in mice may be used to predict the effect of odors in humans. We have previously found that mice fed diets supplemented with engineered nonbrowning potatoes (-PPO) consumed more potato than mice fed diets supplemented with wild-type potatoes (WT). This prompted us to explore a possible role of potato odor in mice preference for nonbrowning potatoes. Taking advantage of two well established neuroscience paradigms, the “open field test” and the “nose-poking preference test”, we performed experiments where mice exploration behavior was monitored in preference assays on the basis of olfaction alone. No obvious preference was observed towards -PPO or WT lines when fresh potato samples were tested. However, when oxidized samples were tested, mice consistently investigated -PPO potatoes more times and for longer periods than WT potatoes. Congruently, humans discriminated WT from -PPO samples with a considerably better performance when oxidized samples were tested than when fresh samples were tested in blind olfactory experiments. Notably, even though participants ranked all samples with an intermediate level of pleasantness, there was a general consensus that the -PPO samples had a more intense odor and also evoked the sense-impression of a familiar vegetable more often than the WT samples. Taken together, these findings suggest that our previous observations might be influenced, at least in part, by differential odors that are accentuated among the lines once oxidative deterioration takes place. Additionally, our results suggest that nonbrowning potatoes, in addition to their extended shelf life, maintain their odor quality for longer periods of time than WT potatoes. To our knowledge this is the first report on the use of an animal model applied to the sensory analysis of a transgenic crop

GMOs in animal agriculture: time to consider both costs and benefits in regulatory evaluations

In 2012, genetically engineered (GE) crops were grown by 17.3 million farmers on over 170 million hectares. Over 70% of harvested GE biomass is fed to food producing animals, making them the major consumers of GE crops for the past 15 plus years. Prior to commercialization, GE crops go through an extensive regulatory evaluation. Over one hundred regulatory submissions have shown compositional equivalence, and comparable levels of safety, between GE crops and their conventional counterparts. One component of regulatory compliance is whole GE food/feed animal feeding studies. Both regulatory studies and independent peer-reviewed studies have shown that GE crops can be safely used in animal feed, and rDNA fragments have never been detected in products (e.g. milk, meat, eggs) derived from animals that consumed GE feed. Despite the fact that the scientific weight of evidence from these hundreds of studies have not revealed unique risks associated with GE feed, some groups are calling for more animal feeding studies, including long-term rodent studies and studies in target livestock species for the approval of GE crops. It is an opportune time to review the results of such studies as have been done to date to evaluate the value of the additional information obtained. Requiring long-term and target animal feeding studies would sharply increase regulatory compliance costs and prolong the regulatory process associated with the commercialization of GE crops. Such costs may impede the development of feed crops with enhanced nutritional characteristics and durability, particularly in the local varieties in small and poor developing countries. More generally it is time for regulatory evaluations to more explicitly consider both the reasonable and unique risks and benefits associated with the use of both GE plants and animals in agricultural systems, and weigh them against those associated with existing systems, and those of regulatory inaction. This would represent a shift away from a GE evaluation process that currently focuses only on risk assessment and identifying ever diminishing marginal hazards, to a regulatory approach that more objectively evaluates and communicates the likely impact of approving a new GE plant or animal on agricultural production systems

The Biochemical and Molecular Basis for the Divergent Patterns in the Biosynthesis of Terpenes and Phenylpropenes in the Peltate Glands of Three Cultivars of Basil

Surface glandular trichomes distributed throughout the aerial parts of sweet basil (Ocimum basilicum) produce and store monoterpene, sesquiterpene, and phenylpropene volatiles. Three distinct basil chemotypes were used to examine the molecular mechanisms underlying the divergence in their monoterpene and sesquiterpene content. The relative levels of specific terpenes in the glandular trichomes of each cultivar were correlated with the levels of transcripts for eight genes encoding distinct terpene synthases. In a cultivar that produces mostly (R)-linalool, transcripts of (R)-linalool synthase (LIS) were the most abundant of these eight. In a cultivar that synthesizes mostly geraniol, transcripts of geraniol synthase were the most abundant, but the glands of this cultivar also contained a transcript of an (R)-LIS gene with a 1-base insertion that caused a frameshift mutation. A geraniol synthase-LIS hybrid gene was constructed and expressed in Escherichia coli, and the protein catalyzed the formation of both geraniol and (R)-linalool from geranyl diphosphate. The total amounts of terpenes were correlated with total levels of terpene synthase activities, and negatively correlated with levels of phenylpropanoids and phenylalanine ammonia lyase activity. The relative levels of geranyl diphosphate synthase and farnesyl diphosphate synthase activities did not correlate with the total amount of terpenes produced, but showed some correlation with the ratio of monoterpenes to sesquiterpenes

Elucidation of the biochemical pathway leading to the biosynthesis of dihydrochalcone compounds in apple

The apple tree (Malus x domestica) is an agriculturally and economically important tree commonly used in food and beverages. Apple has also drawn attention in recent years due to its potential pharmaceutical and nutraceutical applications which are correlated with secondary metabolites. The major phenolic compounds found in apple belong to the class of dihydrochalcones, represented by various phloretin derivatives (e.g. phloridzin, sieboldin, trilobatin). Phloridzin (phloretin 2’-O-glucoside) also occur beside others in strawberry fruits (Fragaria x ananassa), cranberries (Vaccinium macrocarpon) and sweet tea (Lithocarpus polystachus), but in significant lower amounts compared to apple. Beside their contribution to the bitter taste (flavor) of cider and the colour of apple juices due to oxidation products they were also associated with health effects of apple fruits, berries and their processed products (1). The molecular basis of the biosynthesis of dihydrochalcones has only been partially described so far. Phloretin, the aglycone structure of phloridzin is synthesized via the phenylpropanoid way. By the action of specific or also “unspecific” UPD-glucosyltransferases (UGTs) the regiospecific transfer of a sugar residue from a suitable sugar donor is achieved. Two research groups described putative UGTs involved in phloridzin biosynthesis from apple, whereas Md_PGT1 show high substrate specificity to the chalcone producing exclusively the phloridzin (2). However, recombinant Md_UGT71A15 showed broader substrate acceptance towards other flavonoids and also produces the 4’- and 4-O-glucosides from phloretin in significant amounts (1). Gosch et al. (3) assumed that common chalcone synthases (CHSs) are involved in building the core structure from p-hydroxydihydrocinnamoyl-CoA (Fig. 1), which is proposed to be synthesized by an up to now unknown NADPH-dependent dehydrogenase from p-coumaroyl-CoA. In this study the formation of dihydrochalcone which should involve a double bond reductase activity is under investigation. The exact substrates and the identity of these reductases are still unclear. The extensive apple research and the availability of apple genomic and transcriptomic resources make apple an ideal plant to elucidate this key reductase activity that leads to the production of many valuable dihydrochalcones including potent nutraceuticals and sweeteners. To identify genes involved in the synthesis of dihydro-phenolic compound, like dihydrocoumaroyl-CoA in apple fruits, we screened the existing genome database of the Rosaceae for apple proteins with significant sequence similarity to Arabidopsis alkenal double-bond reductase (AKR). We show here that the functionally expressed apple double bound reductase exhibits coumaroyl-CoA reductase activity generating dihydrocoumaroyl-CoA. Our findings contribute to our understanding of dihydrophenols formation in plants