Low intensity light treatment improves purple kale (Brassica oleracea var. sabellica) postharvest preservation at room temperature.

Purple Kale is a vegetable of the Brassicaceae family whose are popularly consumed in recent years due to their high level of healthy components. For consumption, matures leaves are harvested and postharvest senescence is induced. Changes in color leaves due to chlorophyll degradation are the main visible symptoms of postharvest senescence, but there are other changes that affect the nutritional quality of kale. The aim of this study was to investigate if low intensity light pulses could be used to delay postharvest senescence of purple kale stored at room temperature. Daily treatments with 1 h pulses of white or red light were performed. Irradiated samples had approximately 40% higher chlorophyll and protein and more of 20% higher antioxidant capacity and soluble sugar content than control samples regardless of light quality used in treatment (white or red). Both light treatments improve the appearance and quality of kale during storage at room temperature.

Activities of Vacuolar Cysteine Proteases in Plant Senescence.

Plant senescence is accompanied by a marked increase in proteolytic activities, and cysteine proteases (Cys-protease) represent the prevailing class among the responsible proteases. Cys-proteases predominantly locate to lytic compartments, i.e., to the central vacuole (CV) and to senescence-associated vacuoles (SAVs), the latter being specific to the photosynthetic cells of senescing leaves. Cellular fractionation of vacuolar compartments may facilitate Cys-proteases purification and their concentration for further analysis. Active Cys-proteases may be analyzed by different, albeit complementary approaches: (1) in vivo examination of proteolytic activity by fluorescence microscopy using specific substrates which become fluorescent upon cleavage by Cys-proteases, (2) protease labeling with specific probes that react irreversibly with the active enzymes, and (3) zymography, whereby protease activities are detected in polyacrylamide gels copolymerized with a substrate for proteases. Here we describe the three methods mentioned above for detection of active Cys-proteases and a cellular fractionation technique to isolate SAVs.

Genetically engineered Thompson Seedless grapevine plants designed for fungal tolerance: selection and characterization of the best performing individuals in a field trial.

The fungi Botrytis cinerea and Erysiphe necator are responsible for gray mold and powdery mildew diseases, respectively, which are among the most devastating diseases of grapes. Two endochitinase (ech42 and ech33) genes and one N-acetyl-ß-D-hexosaminidase (nag70) gene from biocontrol agents related to Trichoderma spp. were used to develop a set of 103 genetically modified (GM) 'Thompson Seedless' lines (568 plants) that were established in open field in 2004 and evaluated for fungal tolerance starting in 2006. Statistical analyses were carried out considering transgene, explant origin, and plant response to both fungi in the field and in detached leaf assays. The results allowed for the selection of the 19 consistently most tolerant lines through two consecutive years (2007-2008 and 2008-2009 seasons). Plants from these lines were grafted onto the rootstock Harmony and established in the field in 2009 for further characterization. Transgene status was shown in most of these lines by Southern blot, real-time PCR, ELISA, and immunostrips; the most tolerant candidates expressed the ech42-nag70 double gene construct and the ech33 gene from a local Hypocrea virens isolate. B. cinerea growth assays in Petri dishes supplemented with berry juices extracted from the most tolerant individuals of the selected population was inhibited. These results demonstrate that improved fungal tolerance can be attributed to transgene expression and support the iterative molecular and physiological phenotyping in order to define selected individuals from a population of GM grapevines.

Is the electrolyte leakage assay an unequivocal test of membrane deterioration during leaf senescence?

The main symptoms of leaf senescence are the degradation of chlorophyll and proteins (which may be accompanied by ammonium accumulation), and an increase of electrolyte leakage (EL), which has been traditionally attributed to disruption of cell membranes. The aim of this study was to determine if ammonium efflux contributes to the increase EL in senescing barley leaves. During senescence of detached leaves the increase of EL correlated with ammonium leakage (r(2) = 0.82) and ammonium content in tissues (r(2) = 0.73), but not with K(1+) leakage (r(2) = 0.23). Although lower amounts of ammonium accumulated in senescing attached leaves, again changes in EL paralleled ammonium accumulation. EL increased early during senescence even though ion leakage was selective (leaves leaked proportionally more ammonium than K(1+)), and membranes appeared intact as judged from staining with the cell impermeant stain propidium iodide. Detached leaves maintained their capacity to regreen after 3 days of senescence-acceleration in darkness, i.e., membrane integrity was not severely compromised. During the early stages of senescence, EL increases due to ammonium accumulation (possibly resulting from protein degradation) even if there is no massive disruption of cell membranes. Therefore, increased EL in senescing leaves is not an unequivocal symptom of cell membrane damage.