Browsing by Author "Arce Johnson, Patricio"

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    Autopolyploidization and  in vitro regeneration of three blueberry cultivars from leaves and microstems
    (2024) Jarpa Tauler, Gabriela Teresa; Martínez Barradas, Vera Isabel; Romero Romero, Jesús Lucina; Arce Johnson, Patricio
    Blueberries are a fruit with an increasing global demand due to their phytochemical and bioactive compounds content. They are promoted worldwide because of their health benefits. For optimal growth and productivity, blueberry crops need acidic soil pH, specific chilling hours, and an adequate atmospheric temperature. This delicate production equilibrium is under severe threat from climate change, potentially leading to reduced yields and increased cultivation costs unless new cultivars are developed for each edafoclimatic zone. Therefore, considering varietal replacements with more productive cultivars offering higher quality and better adaptability to local conditions is imperative. In this study, we employ polyploidization and in vitro tissue culture to promote variability and lay the foundation for new cultivar development. We report the successful induction of octoploids in three blueberry cultivars, namely 'Biloxi,' 'Legacy,' and 'Duke', through whole-genome duplication. Leaves and microstem explants were exposed to 0.1% colchicine for 24 and 48 hours in in vitro culture. After analyzing the polyploid level of 160 regenerated shoots using DNA flow cytometry, we obtained a total of 18 mutants, consisting of 8 mixoploids and 10 octoploids. The number of chloroplasts in the stomata was analysed by fluorescence microscopy, revealing the duplication of these organelles in the induced octoploid plants. To our knowledge, this represents the first successful induction of octoploids in three blueberry cultivars -'Biloxi,' 'Legacy,' and 'Duke'- achieved by exposing leaves and microstem explants to colchicine in in vitro culture. This technique holds promise as a valuable tool for the development of improved blueberry cultivars.
  • Thumbnail Image
    Item
    Effect of pollination and fertilization on the expression of genes related to floral transition, hormone synthesis and berry development in grapevine
    (ELSEVIER GMBH, 2011) Dauelsberg, Patricia; Tomas Matus, Jose; Josefina Poupin, Maria; Leiva Ampuero, Andres; Godoy, Francisca; Vega, Andrea; Arce Johnson, Patricio
    In the present work, the effect of assisted fertilization on anatomical, morphological and gene expression changes occurring in carpels and during early stages of berry development in Vitis vinifera were studied. Inflorescences were emasculated before capfall, immediately manually pollinated (EP) and fruit development was compared to emasculated but non-pollinated (ENP) and self-pollinated inflorescences (NESP). The diameter of berries derived from pollinated flowers (EP and NESP) was significantly higher than from non-pollinated flowers (ENP) at 21 days after emasculation/pollination (DAE), and a rapid increase in the size of the inner mesocarp, together with the presence of an embryo-like structure, were observed. The expression of gibberellin oxidases (GA200x and GA2ox), anthranilate synthase (related to auxin synthesis) and cytokinin synthase coding genes was studied to assess the relationship between hormone synthesis and early berry development, while flower patterning genes were analyzed to describe floral transition. Significant expression changes were found for hormone-related genes, suggesting that their expression at early stages of berry development (13 DAE) is related to cell division and differentiation of mesocarp tissue at a later stage (21 DAE). Expression of hormone-related genes also correlates with the expression of VvHB13, a gene related to mesocarp expansion, and with an increased repression of floral patterning genes (PISTILLATA and TM6), which may contribute to prevent floral transition inhibiting fruit growth before fertilization takes place. (C) 2011 Elsevier GmbH. All rights reserved.
  • Thumbnail Image
    Item
    Phytoplasma and virus detection in commercial plantings of Vitis vinifera cv. Merlot exhibiting premature berry dehydration
    (UNIV CATOLICA DE VALPARAISO, 2008) Matus, Jose Tomas; Vega, Andrea; Loyola, Rodrigo; Serrano, Carolina; Cabrera, Soledad; Arce Johnson, Patricio
    A new and devastating physiological disorder of Vitis vinifera cv. Merlot was recently reported, known as premature berry dehydration (PBD), which is characterized by plant growth reduction, induction of general senescence and pedicel necrosis in the fruit, causing significant reductions in vineyard production. The causes of this disease remain unclear and previous reports suggest that it may be associated with phloem disruption and water provision. For this reason, any factor causing phloem disturbances could cause an important change in the berry water status. As some micro-organisms have been reported to disrupt phloem flow, we analyzed the occurrence of phytoplasma and viruses in commercial vineyards presenting PBD. In this study, a phytoplasma was detected by electron microscopy and nested PCR while virus infections were diagnosed by RT-PCR in samples collected during two growing seasons. The presence of phytoplasma only in samples from grape plants with PBD suggests that this pathogen may be one of the causal agents of this disorder. We suggest that the influence of other factors, such as virus infections, agronomic handling and environmental conditions also modulate berry dehydration. This is the first study at the microscopic and molecular levels that correlates phytoplasma presence with PBD.
  • Thumbnail Image
    Item
    Post-veraison sunlight exposure induces MYB-mediated transcriptional regulation of anthocyanin and flavonol synthesis in berry skins of Vitis vinifera
    (OXFORD UNIV PRESS, 2009) Thomas Matus, Jose; Loyola, Rodrigo; Vega, Andrea; Pena Neira, Alvaro; Bordeu, Edmundo; Arce Johnson, Patricio; Antonio Alcalde, Jose
    Anthocyanins, flavan-3-ols, and flavonols are the three major classes of flavonoid compounds found in grape berry tissues. Several viticultural practices increase flavonoid content in the fruit, but the underlying genetic mechanisms responsible for these changes have not been completely deciphered. The impact of post-veraison sunlight exposure on anthocyanin and flavonol accumulation in grape berry skin and its relation to the expression of different transcriptional regulators known to be involved in flavonoid synthesis was studied. Treatments consisting of removing or moving aside the basal leaves which shade berry clusters were applied. Shading did not affect sugar accumulation or gene expression of HEXOSE TRANSPORTER 1, although in the leaf removal treatment, these events were retarded during the first weeks of ripening. Flavonols were the most drastically reduced flavonoids following shading and leaf removal treatments, related to the reduced expression of FLAVONOL SYNTHASE 4 and its putative transcriptional regulator MYB12. Anthocyanin accumulation and the expression of CHS2, LDOX, OMT, UFGT, MYBA1, and MYB5a genes were also affected. Other regulatory genes were less affected or not affected at all by these treatments. Non-transcriptional control mechanisms for flavonoid synthesis are also suggested, especially during the initial stages of ripening. Although berries from the leaf removal treatment received more light than shaded fruits, malvidin-3-glucoside and total flavonol content was reduced compared with the treatment without leaf removal. This work reveals that flavonol-related gene expression responds rapidly to field changes in light levels, as shown by the treatment in which shaded fruits were exposed to light in the late stages of ripening. Taken together, this study establishes MYB-specific responsiveness for the effect of sun exposure and sugar transport on flavonoid synthesis.
  • Thumbnail Image
    Item
    PvMYB60 gene, a candidate for drought tolerance improvement in common bean in a climate change context
    (2024) Martínez Barradas, Vera Isabel; Galbiati, Massimo; Barco Rubio, Francisco Antonio; Paolo, Dario; Espinoza, Carmen; Cominelli, Eleonora; Arce Johnson, Patricio
    Background: Common bean (Phaseolus vulgaris) is one of the main nutritional resources in the world, and a low environmental impact source of protein. However, the majority of its cultivation areas are affected by drought and this scenario is only expected to worsen with climate change. Stomatal closure is one of the most important plant responses to drought and the MYB60 transcription factor is among the key elements regulating stomatal aperture. If targeting and mutating the MYB60 gene of common bean would be a valuable strategy to establish more drought-tolerant beans was therefore investigated. Results: The MYB60 gene of common bean, with orthology to the Arabidopsis AtMYB60 gene, was found to have conserved regions with MYB60 typical motifs and architecture. Stomata-specific expression of PvMYB60 was further confirmed by q-RT PCR on organs containing stomata, and stomata-enriched leaf fractions. Further, function of PvMYB60 in promoting stomata aperture was confirmed by complementing the defective phenotype of a previously described Arabidopsis myb60-1 mutant. Conclusions: Our study finally points PvMYB60 as a potential target for obtaining more drought-tolerant common beans in the present context of climate change which would further greatly contribute to food security particularly in drought-prone countries.
  • Thumbnail Image
    Item
    Structure-function relationship between the tobamovirus TMV-Cg coat protein and the HR-like response
    (MICROBIOLOGY SOC, 2008) Ehrenfeld, Nicole; Gonzalez, Angel; Canon, Paola; Medina, Consuelo; Perez Acle, Tomas; Arce Johnson, Patricio
    The tobamovirus TMV-Cg induces an HR-like response in Nicotiana tabacum cv. Xanthi nn sensitive plants lacking the N or N' resistance genes. This response has been characterized by the appearance of necrotic lesions in the inoculated leaf and viral systemic spread, although the defence pathways are activated in the plant. A previous study demonstrated that the coat protein (CP) of TMV-Cg (CPCg) was the elicitor of this HR-like response. We examined the influence of four specific amino acid substitutions on the structure of CPCg, as well as on the development of the host response. To gain insights into the structural implications of these substitutions, a set of molecular dynamic experiments was performed using comparative models of wild-type and mutant CPCg as well as the CP of the U1 strain of TMV (CPU1), which is not recognized by the plants. A P21L mutation produces severe changes in the three-dimensional structure of CPCg and is more unstable when this subunit is laterally associated in silico. This result may explain the observed incapacity of this mutant to assemble virions. Two other CPCg mutations (R46G and S54K) overcome recognition by the plant and do not induce an HR-like response. A double CPCg mutant P21L-S54K recovered its capacity to form virions and to induce an HR-like response. Our results suggest that the structural integrity of the CP proteins is important for triggering the HIR-like response.
  • Thumbnail Image
    Item
    The N-homologue LRR domain adopts a folding which explains the TMV-Cg-induced HR-like response in sensitive tobacco plants
    (ELSEVIER SCIENCE INC, 2008) Stange, Claudia; Matus, Jose Tomas; Dominguez, Calixto; Perez Acle, Tomas; Arce Johnson, Patricio
    Following leaf infection with the tobacco mosaic virus (TMV), Nicotiana species that carry the disease resistance N gene develop a hypersensitive response (HR) that blocks the systemic movement of the virus. TMV-sensitive tobacco plants that lack the N gene develop classical disease symptoms following infection with most of the tobamoviruses. However, upon infection with TMV-Cg, these p, ants display a HR-like response that is unable to limit viral spread. We previously identified the NH gene in sensitive plants; this gene is homologous to the resistance N gene and both belong to the TIR/NBS/LRR family. Isolation and analysis of the NH transcript enabled the prediction of the amino acid sequence in which we detected a leucine-rich repeat domain, proposed to be involved in pathogen recognition. This domain is found in four of five classes of pathogen resistant proteins, in which sequence and structural changes may generate different specificities. In order to study the possible functional role of the LRR domain in the HR-like response, we developed a comparative three-dimensional model for the NH and N gene products, by means of functional and structural domains recognition, secondary structure prediction, domain assignment through profile Hidden Markov Models (HMM) and molecular dynamics (MD) simulations. Based on our results we postulate that the NH protein could adopt a LRR fold with a functional role in the HR-like response. Our two reliable LRR three-dimensional models (N-LRR, NH-LRR) can be used as structural frameworks for future experiments in which the structure-function relationships regarding the protein-protein interaction process may be revealed. Evolutionary aspects of the N and NH genes in Nicotiana species are also discussed. (c) 2007 Elsevier Inc. All rights reserved.