Ectopic expression of Arabidopsis glutaredoxin AtGRXS17 enhances thermotolerance in tomato.

While various signalling networks regulate plant responses to heat stress, the mechanisms regulating and unifying these diverse biological processes are largely unknown. Our previous studies indicate that the Arabidopsis monothiol glutaredoxin, AtGRXS17, is crucial for temperature-dependent postembryonic growth in Arabidopsis. In the present study, we further demonstrate that AtGRXS17 has conserved functions in anti-oxidative stress and thermotolerance in both yeast and plants. In yeast, AtGRXS17 co-localized with yeast ScGrx3 in the nucleus and suppressed the sensitivity of yeast grx3grx4 double-mutant cells to oxidative stress and heat shock. In plants, GFP-AtGRXS17 fusion proteins initially localized in the cytoplasm and the nuclear envelope but migrated to the nucleus during heat stress. Ectopic expression of AtGRXS17 in tomato plants minimized photo-oxidation of chlorophyll and reduced oxidative damage of cell membrane systems under heat stress. This enhanced thermotolerance correlated with increased catalase (CAT) enzyme activity and reduced H2O2 accumulation in AtGRXS17-expressing tomatoes. Furthermore, during heat stress, expression of the heat shock transcription factor (HSF) and heat shock protein (HSP) genes was up-regulated in AtGRXS17-expressing transgenic plants compared with wild-type controls. Thus, these findings suggest a specific protective role of a redox protein against temperature stress and provide a genetic engineering strategy to improve crop thermotolerance.

Sensory analysis of calcium-biofortified lettuce.

Vegetables represent an attractive means of providing increased calcium nutrition to the public. In this study, it was demonstrated that lettuce expressing the deregulated Arabidopsis H(+)/Ca(2+) transporter sCAX1 (cation exchanger 1) contained 25%-32% more calcium than controls. These biofortified lettuce lines were fertile and demonstrated robust growth in glasshouse growth conditions. Using a panel of highly trained descriptive panellists, biofortified lettuce plants were evaluated and no significant differences were detected in flavour, bitterness or crispness when compared with controls. Sensory analysis studies are critical if claims are to be made regarding the efficacy of biofortified foods, and may be an important component in the public acceptance of genetically modified foods.

Synergetic effect of the Onion CHI gene on the PAP1 regulatory gene for enhancing the flavonoid profile of tomato skin.

Tomatoes are known to have ameliorative effects on cardiovascular disease and cancer. The nutritional value of tomatoes can be enhanced by increasing flavonoids content through genetic modification. The regulatory gene PAP1 (production of anthocyanin pigment 1) from Arabidopsis is reported to increase initial flavonoid flux and anthocyanin content. The structural gene CHI from Alium cepa increases flavonol content. However, the number of structural genes that can be transferred to plants is limited. To solve this problem, for the first time, we produced gene stacking transgenic tomato, in which Arabidopsis PAP1 (production of anthocyanin pigment 1) was stacked with an onion CHI by crossing. This procedure resulted in increased rutin and total anthocyanin content of as much as 130 and 30 times more, respectively, than the content in wild tomato skin, compared with 2.3 and 3 times more flavonol content, and 1 and 1.5 times more anthocyanin content in unstacked FLS and PAP1 tomatoes, respectively.

Effects of population, age, and cultivation methods on ginsenoside content of wild American ginseng (Panax quinquefolium).

Genotype and environmental effects on ginsenoside content among eight wild populations of American ginseng (Panax quinquefolium) were investigated. Root concentrations of six ginsenosides were determined at the time of collection of plants from the wild (T0) and 2 years (T2) after transplanting roots from each of the eight populations to each of two different forest garden locations. Both location and population had significant effects on root and shoot growth. Overall, ginsenoside Rb1 was most abundant, followed by Rg1 and Re. Concentrations of Rg1 and Re were inversely related among and within populations. The relative ranking of populations differed depending upon the particular ginsenoside and sampling time. The relative importance of genotype and environment was not the same for all ginsenosides. Ginsenoside Re was influenced by population but not location, whereas Rb1, Rc, and Rb2 were influenced only by location (environment), while Rg1 and Rd were influenced by both. Ginsenoside levels were consistently lower, but growth was consistently higher at the more intensively managed garden location.

Consumer sensory analysis of high flavonoid transgenic tomatoes.

UNLABELLED: Tomatoes have ameliorative effects on cardiovascular disease and cancer. In this study, metabolic engineering of flavonoids was utilized to improve the nutritional value of tomatoes by increasing flavonol and anthocyanin content. Total flavonol content was significantly increased in both the peel and flesh using the onion chalcone isomerase (CHI) gene. The Delila (Del) and Rosea1 (Ros1) genes from the snapdragon Antirrhinum majus were concomitantly expressed to produce an anthocyanin-rich tomato which was purple in color. Sensory evaluation by a panel of 81 untrained consumers revealed no significant difference in liking of color or texture between CHI, Del/Ros1, and wild-type tomatoes. Consumers reported marginal but significantly higher preference for the flavor and overall liking of CHI tomatoes over Del/Ros1 and wild-type tomatoes. This study is the first to report the results of sensory tests of transgenic tomatoes by a consumer panel representing the general consuming public. PRACTICAL APPLICATION: Transgenic procedures were used to increase the flavonol and anthocyanin contents of tomatoes. An untrained consumer panel scored flavor and overall liking of the 2 transgenic tomatoes higher than wild-type tomatoes and reported no difference in liking of texture or color between the 3 tomatoes. After participating in the sensory study, 14% of the panelists changed their attitudes positively toward transgenic vegetables and 96% of the consumers on the panel reported that they would buy transgenic food if they believed that it would promote health.

Utilization of RAPD markers to assess genetic diversity of wild populations of North American ginseng (Panax quinquefolium).

The Catskill Mountains of New York State are an important source of wild-collected American ginseng (Panax quinquefolium) and, increasingly, of woods-cultivated ginseng. The objective of this study was to assess genetic diversity among 9 different wild ginseng populations in and adjacent to the Catskill Mountain region of New York State and to compare these to wild populations from other states including Kentucky, Tennessee, North Carolina, Pennsylvania, and Virginia, and one cultivated population from Wisconsin. Randomly amplified polymorphic DNA (RAPD) markers were used to estimate the genetic distance among samples from the 15 populations. Pooled DNA from 10 plants of each of 8 New York populations was initially screened with 64 random primers; subsequently, the 15 primers that exhibited the greatest number of reproducible polymorphic markers were selected for further experimentation. Gel electrophoresis with the selected 15 primers produced 124 highly reproducible polymorphic bands. The ratio of discordant bands to total bands scored was used to estimate the genetic distance within and among populations. Multidimensional scaling (MDS) of the relation matrix showed distinctly separate clusters between New York and non-New York populations, indicating separation between these two groupings. The MDS analysis was confirmed using pooled chi-square tests for fragment homogeneity. This study shows that RAPD markers can be used as population-specific markers for Panax quinquefolium, and may eventually be utilized as markers for ginsenoside assessment.