Project description:Comparative profiling of fresh-cut lettuce samples treated with an alternative washing solution (PAA) with respect to standard treated samples STD (SH-treated).We generated a comprehensive repertory of transcripts useful to study the global change induced by two sanitizer in different time points of storage (T1, T3, and T6).
Project description:An untargeted metabolomics approach using UPLC-ESI-QTOF-MS was performed to explore the metabolome of iceberg lettuce and the changes related to storage time and genetics. Two cultivars with different browning susceptibility, fast- browning (FB) and slow-browning (SB) were studied juts after cutting (d0) and after 5 days of storage (d5). Extraction, metabolic profiling, and data-pretreatment procedures were optimized to obtain a robust and reliable data set. Preliminary principal component analysis (PCA) and hierarchical cluster analysis (HCA) of the full dataset (around 8551 extracted, aligned and filtered metabolites) showed a clear separation between the different samples (FB-d0, FB-d5, SB-d0, and SB-d5), highlighting a clear storage time-dependent effect. After statistical analysis applying Student´s t-test, 536 metabolites were detected as significantly different between d0 and d5 of storage in FB and 633 in SB. Some metabolites (221) were common to both cultivars. Out of these significant compounds, 22 were tentatively identified by matching their molecular formulae with those previously reported in the literature. Five families of metabolites were identified, some of them closely related to quality loss: amino acids, phenolic compounds, sesquiterpene lactones, fatty acids, and lysophospholipids. All compounds showed a clear trend to decrease at d5 except phenolic compounds that increased after storage. Overall, cutting and storage were shown to have a significant impact on the changes of lettuce metabolomics, with different trends depending on the browning susceptibility.
Project description:In the present study, we found a new walnut germplasm from wild Juglans cathayensis population, which presented white husk that did not brown. We compared the transcriptome between the fresh-cut browning (control) and white husks of the Chinese walnut using Illumina HiSeq 4000 platform
Project description:Lettuce is one of most consumed vegetables globally. This crop is susceptible to abiotic stresses. To understand the molecular mechanisms of stress response in lettuce, global transcriptome analysis was conducted. This analysis revealed distinctive temporal expression patterns among the stress-regulated genes in lettuce plants exposed to abiotic stresses
Project description:Nisin application delays growth of Listeria monocytogenes on fresh-cut iceberg lettuce, while the bacterial community structure changes within one week of storage.
Project description:Visual assessments are used for evaluating the quality of food products, such as fresh-cut lettuce packaged in bags with modified atmosphere. We have compared the accuracy and the reliability of visual evaluations of decay on fresh-cut lettuce performed with experienced and inexperienced raters. In addition, we have analyzed decay data from over 4.5 thousand bags to determine the optimum timing for evaluations to detect differences among accessions. Lin's concordance coefficient (ρc) that takes into consideration both the closeness of the data and the conformance to the identity line showed high repeatability (intra-rater reliability, ρc = 0.97), reproducibility (inter-rater reliability, ρc = 0.92), and accuracy (ρc = 0.96) for experienced raters. Inexperienced raters did not perform as well and their ratings showed decreased repeatability (ρc = 0.93), but even larger reduction in reproducibility (ρc = 0.80) and accuracy (ρc = 0.90). We have detected that 5.3% of ratings were outside of the 95% limits of agreement. These under- or overestimates were predominantly found for bags with intermediate levels of decay, which corresponds to the middle of the rating scale. This occurs because intermediate amounts of decay are more difficult to discriminate than extremes. The frequencies of aberrant ratings for experienced raters ranged from 0.6% to 4.4% (mean = 2.1%), for inexperienced raters the frequencies were substantially higher, ranging from 6.1% to 15.6% (mean = 9.4%). Therefore, we recommend that new raters receive training that includes practical examples in this range of decay, use of standard area diagrams, and continuing interaction with experienced raters (consultation during actual rating). Very high agreement among experienced raters indicate that visual ratings can be successfully used for evaluations of decay, until a more objective, rapid, and affordable method is developed. We recommend evaluating samples at multiple time points until 42 days after processing (about 80% decay on average) and then combining these individual ratings into the area under the decay progress stairs (AUDePS) score. Applying this approach, experienced evaluators can accurately detect difference among lettuce accessions and identify lettuce cultivars with reduced decay.
Project description:Bolting is a key process in the growth and development of lettuce (Lactuca sativa L.). High temperature can induce earlier bolting which decreases in both quality and production of lettuce. However, knowledge underlying lettuce bolting is still lacking. To better understand the molecular basis of bolting, a comparative proteomics analysis was conducted on lettuce stems in the bolting period induced by high temperature (33 °C) compared with a control (20 °C) using iTRAQ-based proteomics, phenotypic measures, and biological verifications. High temperature induced lettuce bolting, while control temperature did not. Of the 6656 proteins identified, 758 proteins significantly altered their expression level induced by high-temperature relative to the control, of which 409 were up-regulated and 349 down-regulated. Proteins with abundance level change were mainly involved in photosynthesis, carbohydrate metabolism, stress response, hormone synthesis, and signal transduction. These differential proteins were mainly enriched in pathways associated with photosynthesis and tryptophan metabolism involving in auxin (IAA) biosynthesis. Among the differentially expressed proteins associated with photosynthesis and tryptophan metabolism were up-regulated. Moreover, in gibberellin (GA) biosynthesis pathway, 10 of main enzymes of P450 were up-regulated. Proteins related to SAUR and GRP, implicated in IAA and GA signal transduction were up-regulated, and the phosphorylation and ubiquitination related proteins regulating IAA and GA signal transduction were also induced. These findings indicate that a high temperature enhances the function of photosynthesis, IAA and GA synthesis and signal transduction to promote the process of bolting, which is in line with the physiology and transcription levels of IAA and GA metabolism. Our data provide a first comprehensive dataset for gaining novel understanding of the molecular basis underlying lettuce bolting induced by high temperature. It is potentially important for further functional analysis and genetic manipulation for molecular breeding to breed new cultivar of lettuce to restrain early bolting, which is vital for improving vegetable quality.
2019-11-12 | PXD008610 | Pride
Project description:Microbial diversity on fresh-cut lettuce
Project description:Enzymatic browning on the cut edge of lettuce significantly limits its quality and shelf life. To characterize its molecular mechanisms, we performed comparative transcriptome analysis of three Romaine lettuce cultivars, Parris Island Cos (PC) with low browning potential, Tall Guzmaine (TG) with high degree of browning and Clemente (CL), a medium degree of browning cultivar derived from TG x PC. Before cutting, the phenylpropanoid and oxidative stress genes, such as PAL1, MYB1 and PPO were up-regulated in PC as compared to TG, while the expressions of genes involved in auxin, cytokinin hormone signalings and defense, such as ARF, AHP and PTI in PC were higher than TG. The transcript levels of all these genes in CL were somewhere between TG and PC. On day 3 after cutting when browning was shown up in TG, the expression of these phenylpropanoid and oxidative stress genes were remarkably increased in all three cultivars, even though their levels in TG were still higher than those in PC and CI. In comparison, expressions of the hormone and defense genes were reduced in all three cultivars, but their levels in PC were higher than CI and TG. Exogenous application of IAA and 6-BA inhibited lettuce browning possibly by alleviating the burst of those browning related genes, such as PAL1 and PPO1. These results demonstrate that lettuce tissue browning is controlled by reduced growth hormone (mainly auxin) level and increased phenolics biosynthesis and oxidation. This study provides the useful knowledge and functional markers for lettuce breeders and industry to select low tissue browning cultivar and manage lettuce quality during storage and processing.