We have identified a plasma membrane Na + /H + antiporter gene from tomato (Solanum lycopersicum), SlSOS1, and used heterologous expression in yeast to confirm that SlSOS1 was the functional homolog of AtSOS1. Using posttranscriptional gene silencing, we evaluated the role played by SlSOS1 in long-distance Na + transport and salt tolerance of tomato. Tomato was used because of its anatomical structure, more complex than that of Arabidopsis, and its agricultural significance. Transgenic tomato plants with reduced expression of SlSOS1 exhibited reduced growth rate compared to wild-type (WT) plants in saline conditions. This sensitivity correlated with higher accumulation of Na + in leaves and roots, but lower contents in stems of silenced plants under salt stress. Differential distribution of Na + and lower net Na + flux were observed in the xylem sap in the suppressed plants. In addition, K + concentration was lower in roots of silenced plants than in WT. Our results demonstrate that SlSOS1 antiporter is not only essential in maintaining ion homeostasis under salinity, but also critical for the partitioning of Na + between plant organs. The ability of tomato plants to retain Na + in the stems, thus preventing Na + from reaching the photosynthetic tissues, is largely dependent on the function of SlSOS1.

The location of major quantitative trait loci (QTL) contributing to stem and leaf [Na

The effect of ozone treatment on the postharvest quality of strawberry was evaluated. Strawberry fruits (Fragaria x ananassa Duch. cv. Camarosa) were stored at 2 degrees C in an atmosphere containing ozone (0.35 ppm). After 3 days at 2 degrees C, fruits were moved to 20 degrees C to mimic retail conditions (shelf life). The changes in several quality parameters such as fungal decay, color, sugar and acids distribution, and aroma were evaluated during the strawberries' shelf life. Ozone treatment was ineffective in preventing fungal decay in strawberries after 4 days at 20 degrees C. Significant differences in sugars and ascorbic acid content were found in ozone-treated strawberries. At the end of cold storage, the vitamin C content of ozonated strawberries was 3 times that of control fruits. A detrimental effect of ozone treatment on strawberry aroma was observed, with a 40% reduced emission of volatile esters in ozonated fruits.

An analytical procedure to determine major sugars and organic acids, including vitamin C, in fruits was developed using a C18 Sep-Pak cleanup process and an ion exclusion HPLC column. Dual UV monitoring and refractive index were performed for detection. To attain optimal separation and quantitation, 0.0085N H2SO4 was used as the mobile phase and the column temperature was maintained at 23 °C. This procedure was compared to others for the individual quantitation of sugars, organic acids, and vitamin C. Recovery and reproducibility of this analytical procedure were quite acceptable for strawberry and four other common fruits, allowing the analysis of all the components using a single-injection HPLC analysis in <22 min. Keywords: Simultaneous analysis; high-performance liquid chromatography; sugars; organic acids; vitamin C; strawberry; fruits

Furaneol, mesifurane, and furaneol glucoside contents during ripening of four strawberry varieties (Oso Grande, Chandler, Tudla, and I-101) have been analyzed. Patterns of furanone contents were similar for the four varieties, amounts increasing during ripening to reach the highest values at the overripe stage. However, furaneol and derivatives differed quantitatively among varieties. The amount of furaneol shown by Oso Grande at the overripe stage is the highest so far reported (37.05 μg/g fw). The highest content in mesifurane and furaneol glucoside was found in the I-101 variety, at the overripe stage, 23.5 and 13.2 μg/g fw, respectively. Results obtained in eight different varieties, at commercial maturity stage, also showed quantitative differences. Strawberries were stored at 1 °C for 2 days to simulate refrigerated transport and then kept for 7 days at 17 °C to simulate the shelf life period. At 17 °C, the amount of mesifurane and furaneol glucoside increased more than 50% with concomitant loss of furaneol. Keywords: Strawberry; flavor; furanones

The Ca 2+ -dependent SOS pathway has emerged as a key mechanism in the homeostasis of Na + and K + under saline conditions. We have identified and functionally characterized the gene encoding the calcineurin-interacting protein kinase of the SOS pathway in tomato, SlSOS2. On the basis of protein sequence similarity and complementation studies in yeast and Arabidopsis, it can be concluded that SlSOS2 is the functional tomato homolog of Arabidopsis AtSOS2 and that SlSOS2 operates in a tomato SOS signal transduction pathway. The biotechnological potential of SlSOS2 to provide salt tolerance was evaluated by gene overexpression in tomato (Solanum lycopersicum L. cv. MicroTom). The better salt tolerance of transgenic plants relative to non-transformed tomato was shown by their faster relative growth rate, earlier flowering and higher fruit production when grown with NaCl. The increased salinity tolerance of SlSOS2-overexpressing plants was associated with higher sodium content in stems and leaves and with the induction and up-regulation of the plasma membrane Na /H+ (LeNHX2 and LeNHX4) antiporters, responsible for Na + extrusion out of the root, active loading of Na + into the xylem, and Na + and K + compartmentalization.

Four strawberry (Fragaria ananassa × Duch.) varieties Oso Grande, Chandler, Tudla, and I-101) were studied in relation to their alcohol acyltransferase (AAT) activity. AAT activity profile during fruit development and ripening was determined for each variety. The highest AAT activity value corresponded to Oso Grande, which is also the variety showing the earliest maximum peak of AAT activity. The effect of passive modified atmosphere (MA) storage on strawberry AAT was also studied. An increase in AAT activity was found in strawberries stored under high CO2 (>30%). This higher level of AAT activity could be attributed to a detoxifying function of AAT that might be activated to eliminate ethanol generated by fermentation. Data obtained show a good correlation between AAT activity and flavor quality in strawberries. Keywords: Strawberry; flavor; ester biogenesis; alcohol acyltransferase

The enzymes lipoxygenase and hydroperoxide lyase have been identified in strawberry (Fragariax ananassa Duch.) var. Camarosa. Their subcellular localization, substrate preference, and product specificity were determined in mature strawberry fruits. The activity of both enzymes was located mainly in the microsomal fraction. Linolenic acid was the preferred substrate for strawberry lipoxygenase, forming 13- and 9-hydroperoxides of this acid in the proportion 70:30. The strawberry hydroperoxide lyase cleaves 13-hydroperoxide of linoleic (13% relative activity) and linolenic (100% relative activity) acids to form hexanal and (3Z)-hexenal, respectively. Both enzyme activities and endogenous content of volatile aldehydes formed by sequential action of lipoxygenase-hydroperoxide lyase were evaluated during strawberry development and ripening. A sequential enzymatic pathway for the formation of green odor compounds in strawberry is proposed.