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Lidon F.C.,New University of Lisbon | Ramalho J.C.,Institute Investigacao Cientifica Tropical Ip Iict
Journal of Agronomy and Crop Science | Year: 2014

The molecular mechanism to control the oxidative burst exerted by Mn accumulation in rice (Oryza sativa L.) plants, grown in hydroponics containing 0.5, 2 and 8 mg l-1 Mn and irradiated with a total biological effective UV-B irradiation of 20.825 kJ m-2, was investigated in the chloroplasts at the 15th and 21st days after germination. In both experimental periods, Mn accumulation kinetics in the leaves and in the chloroplast lamellae displayed overall increases. Coupled to higher membrane selectivity, superoxide production and acyl lipids peroxidation in the thylakoids decreased, prompting upper rates of the Hill and Mehler reactions. Connected to UV-B irradiation, higher accumulated Mn in thylakoids was found to be chelated in a 36.5 kDa protein, with Mn/protein ratio of about 1 and high content of Gln, Asp, Glu, Leu and Gly, being its EPR spectrum characteristic of high-spin Mn(II), in a S = 5/2 ground state. As this protein exhibited enzymatic catalysis of superoxide dismutation, it was concluded that, under UV-B irradiation, the high internal tolerance of Oryza sativa L. to Mn during the vegetative growth also triggers the synthesis of a manganese protein that mimics superoxide dismutase functioning, therefore furnishing an additional intimate protection against oxidative stress. © 2014 Blackwell Verlag GmbH.

Domingos S.,University of Lisbon | Domingos S.,Institute Investigacao Cientifica Tropical Ip Iict | Fino J.,University of Lisbon | Paulo O.S.,University of Lisbon | And 2 more authors.
Plant Science | Year: 2016

Flower-to-fruit transition depends of nutrient availability and regulation at the molecular level by sugar and hormone signalling crosstalk. However, in most species, the identities of fruit initiation regulators and their targets are largely unknown. To ascertain the main pathways involved in stenospermocarpic table grape fruit set, comprehensive transcriptional and metabolomic analyses were conducted specifically targeting the early phase of this developmental stage in 'Thompson Seedless'. The high-throughput analyses performed disclosed the involvement of 496 differentially expressed genes and 28 differently accumulated metabolites in the sampled inflorescences. Our data show broad transcriptome reprogramming of molecule transporters, globally down-regulating gene expression, and suggest that regulation of sugar- and hormone-mediated pathways determines the downstream activation of berry development. The most affected gene was the SWEET14 sugar transporter. Hormone-related transcription changes were observed associated with increased indole-3-acetic acid, stimulation of ethylene and gibberellin metabolisms and cytokinin degradation, and regulation of MADS-box and AP2-like ethylene-responsive transcription factor expression. Secondary metabolism, the most representative biological process at transcriptome level, was predominantly repressed. The results add to the knowledge of molecular events occurring in grapevine inflorescence fruit set and provide a list of candidates, paving the way for genetic manipulation aimed at model research and plant breeding. © 2015 Elsevier Ireland Ltd.

Goulao L.F.,Institute Investigacao Cientifica Tropical Ip Iict | Fortunato A.S.,Institute Investigacao Cientifica Tropical Ip Iict | Ramalho J.C.,Institute Investigacao Cientifica Tropical Ip Iict
Plant Molecular Biology Reporter | Year: 2012

Selection and validation of appropriate reference genes should be the first step to consider in experiments based on quantitative real-time polymerase chain reaction (qRT-PCR). In this study, ten candidate genes were investigated for their stability as suitable reference genes in qRT-PCR data normalization using a diverse set of 12 Coffea cDNAs from plants from three different species/genotypes exposed to single or multiple abiotic stresses (drought and chilling, alone or in combination). Primer amplification efficiencies were calculated for all of the selected genes and varied according to each individual genotype. The expression of each gene was measured by qRT-PCR to evaluate its stability. A multiple analytical approach was followed, based on consensus merged data from four different complementary statistics, namely geNorm, BestKeeper, NormFinder, and coefficient of variation, which produced comparable but not identical results. According to this approach, the most suitable sets of reference genes for data normalization in the five experimental datasets are (1) total assay: GAPHD, Cycl, and UBQ10; (2) genotype: GAPDH, UBQ10, Ap47, and EF-1A; (3) cold stress: UBQ10, GAPDH, ACT, and EF-1A; (4) drought stress: GAPDH, ACT, EF1A, and Apt; and (5) multiple stress: UBQ10, GAPDH, ACT, and elf-4A. Normalization of gene expression using these selected genes was validated by examination of the expression of the photosynthetic-related ApoA2 gene in samples from non-stressed and stressed plants. Our results are useful to assist studies on Coffea physiology with the aim of breeding for increased tolerance to abiotic stress conditions. © 2011 Springer-Verlag.

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