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Daurelio L.D.,National University of Rosario | Tondo M.L.,National University of Rosario | Romero M.S.,Santa Fe Institute | Merelo P.,European Molecular Biology Laboratory | And 4 more authors.
Functional Plant Biology | Year: 2015

Plants are constantly exposed to stress factors. Biotic stress is produced by living organisms such as pathogens, whereas abiotic stress by unfavourable environmental conditions. In Citrus species, one of the most important fruit crops in the world, these stresses generate serious limitations in productivity. Through biochemical and transcriptomic assays, we had previously characterised the Citrus sinensis (L.) Osbeck nonhost response to Xanthomonas campestris pv. vesicatoria (Doidge), in contrast to Asiatic citrus canker infection caused by Xanthomonas citri subsp. citri (Hasse). A hypersensitive response (HR) including changes in the expression of several transcription factors was reported. Here, a new exhaustive analysis of the Citrus sinensis transcriptomes previously obtained was performed, allowing us to detect the over-representation of photosynthesis, abiotic stress and secondary metabolism processes during the nonhost HR. The broad downregulation of photosynthesis-related genes was correlated with an altered photosynthesis physiology. The high number of heat shock proteins and genes related to abiotic stress, including aquaporins, suggests that stresses crosstalk. Additionally, the secondary metabolism exhibited lignin and carotenoid biosynthesis modifications and expression changes in the cell rescue GSTs. In conclusion, novel features of the Citrus nonhost HR, an important part of the plants' defence against disease that has yet to be fully exploited in plant breeding programs, are presented. Source


Estornell L.H.,Institute Valencia dInvestigacions Agraries | Wildhagen M.,University of Oslo | Perez-Amador M.A.,Polytechnic University of Valencia | Talon M.,Institute Valencia dInvestigacions Agraries | And 2 more authors.
Frontiers in Plant Science | Year: 2015

Organ abscission is an important process in plant development and reproduction. During abscission, changes in cellular adhesion of specialized abscission zone cells ensure the detachment of infected organs or those no longer serving a function to the plant. In addition, abscission also plays an important role in the release of ripe fruits. Different plant species display distinct patterns and timing of organ shedding, most likely adapted during evolution to their diverse life styles. However, it appears that key regulators of cell separation may have conserved function in different plant species. Here, we investigate the functional conservation of the citrus ortholog of the Arabidopsis peptide ligand INFLORESCENCE DEFICIENT IN ABSCISSION (AtIDA), controlling floral organ abscission. We discuss the possible implications of modifying the citrus IDA ortholog for citrus fruit production. © 2015 Estornell, Wildhagen, Pérez-Amador, Talón, Tadeo and Butenko. Source


Caruso M.,University of Catania | Merelo P.,Institute Valencia dInvestigacions Agraries | Distefano G.,University of Catania | La Malfa S.,University of Catania | And 4 more authors.
BMC Plant Biology | Year: 2012

Background: Reproductive biology in citrus is still poorly understood. Although in recent years several efforts have been made to study pollen-pistil interaction and self-incompatibility, little information is available about the molecular mechanisms regulating these processes. Here we report the identification of candidate genes involved in pollen-pistil interaction and self-incompatibility in clementine (Citrus clementina Hort. ex Tan.). These genes have been identified comparing the transcriptomes of laser-microdissected stylar canal cells (SCC) isolated from two genotypes differing for self-incompatibility response ('Comune', a self-incompatible cultivar and 'Monreal', a self- compatible mutation of 'Comune').Results: The transcriptome profiling of SCC indicated that the differential regulation of few specific, mostly uncharacterized transcripts is associated with the breakdown of self-incompatibility in 'Monreal'. Among them, a novel F-box gene showed a drastic up-regulation both in laser microdissected stylar canal cells and in self-pollinated whole styles with stigmas of 'Comune' in concomitance with the arrest of pollen tube growth. Moreover, we identify a non-characterized gene family as closely associated to the self-incompatibility genetic program activated in 'Comune'. Three different aspartic-acid rich (Asp-rich) protein genes, located in tandem in the clementine genome, were over-represented in the transcriptome of 'Comune'. These genes are tightly linked to a DELLA gene, previously found to be up-regulated in the self-incompatible genotype during pollen-pistil interaction.Conclusion: The highly specific transcriptome survey of the stylar canal cells identified novel genes which have not been previously associated with self-pollen rejection in citrus and in other plant species. Bioinformatic and transcriptional analyses suggested that the mutation leading to self-compatibility in 'Monreal' affected the expression of non-homologous genes located in a restricted genome region. Also, we hypothesize that the Asp-rich protein genes may act as Ca 2+"entrapping" proteins, potentially regulating Ca 2+homeostasis during self-pollen recognition. © 2012 Caruso et al; licensee BioMed Central Ltd. Source


Estornell L.H.,Institute Valencia dInvestigacions Agraries | Gomez M.D.,Polytechnic University of Valencia | Perez-Amador M.A.,Polytechnic University of Valencia | Talon M.,Institute Valencia dInvestigacions Agraries | Tadeo F.R.,Institute Valencia dInvestigacions Agraries
Acta Horticulturae | Year: 2016

The separation events of abscission occur in a group of functionally specialized cells known as the abscission zone (AZ). This tissue differentiates simultaneously with the development of lateral organs formed from the shoot apical meristem (SAM) in a limited number of morphological locations on the plant body (primary AZs) or after the development of lateral organs in a position that is not predetermined by the morphology of the plant (secondary AZs). In addition, differentiation and activation of secondary AZs are almost concurrent processes whereas primary AZs remain inactive until they acquire the competence to respond to abscission signals. Research on abscission has been mainly focused on the analysis of primary AZs while secondary AZs have drawn limited attention. In citrus pistils, the unit formed by the stigma and the style usually abscises several weeks after anthesis. Differentiation of the style AZ takes place in the basal portion of the style near the ovary. However, style AZ differentiation and activation does not occur in certain cultivars of citrus that retain the style throughout fruit development and maturation. In order to study style AZ differentiation and activation we performed a comparative anatomical and molecular analysis in pistils of both 'Navelate' orange and 'Bergamot of Calabria' showing regular stylar abscission and persisting styles, respectively. A better understanding of the molecular mechanisms underlying stylar abscission may be the starting point to envisage strategies to prevent fertilization and ensure the production of seedless citrus fruits without the need of avoiding pollination. Source


Tadeo F.R.,Institute Valencia dInvestigacions Agraries | Agusti J.,Institute Valencia dInvestigacions Agraries | Agusti J.,Gregor Mendel Institute of Molecular Plant Biology | Merelo P.,Institute Valencia dInvestigacions Agraries | And 4 more authors.
Acta Horticulturae | Year: 2012

Abscission events in citrus allow the detachment of entire organs, both vegetative (buds, leaves) and reproductive (flowers, ovaries, fruitlets, mature fruits). This is achieved by the modification of cellular adhesion in a discrete group of specialized cells differentiated in predictable positions, known as abscission zones (AZs). Thus, abscission facilitates several key processes for citrus biology that, in an agricultural context, represent a major limiting factor for crop yield. In this regard, understanding the regulation of abscission is an important item for the citrus fruit industry. Several functional genomic approaches are currently being used to gain insights into the regulation of citrus abscission and to provide potential candidate genes for further biotechnological applications. These include: (a) the development of an expressed sequence tag (EST) dataset from abscission activated AZs and the analysis of ESTs distribution in organs to reveal AZ-preferential gene expression during abscission activation, (b) comparative transcriptomic analysis using cDNA microarrays and laser microdissected tissues (AZ cells, petiole and fruit rind cells flanking AZs), and (c) functional characterization of putative abscission-associated citrus genes in Arabidopsis thaliana and rice (Oryza sativa). Source

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