Salcedo-Jordán, Andrés F.

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    Time course gene expression profiling of cassava roots (Manihot esculenta) under physiological postharvest deterioration
    (2011) Salcedo-Jordán, Andrés F.; Siritunga, Dimuth; College of Arts and Sciences - Sciences; Macchiavelli, Raúl; Montalvo, Rafael; Department of Biology; Aponte, Nilda E.
    The economic expansion of tropical root crop cassava is threatened by the rapid physiological postharvest deterioration (PPD) developed within the first 48 hours after harvest. This phenomenon contributes substantially to economic losses for cassava farmers, and limits the production of cassava for industrial purposes. Genetic variation of cassava with potential to solve the problem has been scarce, as well as information about genes involved in PPD. In an effort to increase our understanding about PPD, Puerto Rican cassava germplasm collection was evaluated for its potential for tolerance to PPD testing both visual and digital image analysis methodologies. PPD evaluation identified two cassava accessions (MCol 2215, high PPD, and SM 494-1, low PPD) with contrasting levels of PPD. These accessions were used to study the changes in gene expression of a selection of 21 genes. Selected genes are associated with several biological processes include biosynthesis, plant defense, response to wounding, oxidative stress, program cell death, cyanide detoxification, cell wall, water transport and sulfur metabolism. Expression patterns were evaluated in cortex and pith tissue from roots of contrasting accessions subject to varying times after harvest (0, 1, 24, 72, and 120 hours). Changes in gene expression were evaluated using real time PCR. Prior to the assessment of expression patterns of the target genes, the best reference genes for normalizing were obtained among five candidates. Multivariate analysis tools were used for the analysis of all data obtained, allowing the identification of coordinated gene expression patterns which were tested through a confirmatory statistical analysis. Results obtained suggest a model that explains the tolerance observed based in spatiotemporal changes of gene expression in cortex and pith tissue, these changes would be affecting Reactive Oxigen Species (ROS) activity, wound repair and hormone synthesis.