Role of the yeast multidrug transporter Qdr2 in cation homeostasis and the oxidative stress response

We have identified QDR2 in a screening for genes able to confer tolerance to sodium and/or lithium stress upon overexpression. Qdr2 is a multidrug transporter of the major facilitator superfamily, originally described for its ability to transport the antimalarial drug quinidine and the herbicide barban. To identify its physiological substrate, we have screened for phenotypes dependent on QDR2 and found that Qdr2 is able to transport monovalent and divalent cations with poor selectivity, as shown by growth tests and the determination of internal cation content. Moreover, strains overexpressing or lacking QDR2 also exhibit phenotypes when reactive oxygen species- producing agents, such as hydrogen peroxide or menadione were added to the growth medium. We have also found that the presence of copper and hydrogen peroxide repress the expression of QDR2. In addition, the copper uptake of a qdr2 mutant strain is similar to a wild type, but the extrusion is clearly impaired. Based on our results, we propose that free divalent copper is the main physiological substrate of Qdr2. As copper is a substrate for several redox reactions that occur within the cytoplasm, its function in copper homeostasis explains its role in the oxidative stress response.This work was supported by grants PAID-06-10-1496 of the Universitat Politècnica de València (Valencia, Spain), PROMETEO/2010/038 of the ‘Consellería de Educación’ (Valencia, Spain), by grant BFU2011-30197-C03-03 and by grant BFU2011-22526 from the Ministerio de Ciencia e Innovación (Madrid, Spain)

Identification of a GCC transcription factor responding to fruit colour change events in citrus through the transcriptomic analyses of two mutants

14 páginas, 6 figuras, 3 tablas.[Background]: External ripening in Citrus fruits is morphologically characterized by a colour shift from green to orange due to the degradation of chlorophylls and the accumulation of carotenoid pigments. Although numerous genes coding for enzymes involved in such biochemical pathways have been identified, the molecular control of this process has been scarcely studied. In this work we used the Citrus clementina mutants 39B3 and 39E7, showing delayed colour break, to isolate genes potentially related to the regulation of peel ripening and its physiological or biochemical effects. [Results]: Pigment analyses revealed different profiles of carotenoid and chlorophyll modification in 39B3 and 39E7 mutants. Flavedo from 39B3 fruits showed an overall delay in carotenoid accumulation and chlorophyll degradation, while the flavedo of 39E7 was devoid of the apocarotenoid β-citraurin among other carotenoid alterations. A Citrus microarray containing about 20,000 cDNA fragments was used to identify genes that were differentially expressed during colour change in the flavedo of 39B3 and 39E7 mutants respect to the parental variety. The results highlighted 73 and 90 genes that were respectively up- and down-regulated in both mutants. CcGCC1 gene, coding for a GCC type transcriptional factor, was found to be down-regulated. CcGCC1 expression was strongly induced at the onset of colour change in the flavedo of parental clementine fruit. Moreover, treatment of fruits with gibberellins, a retardant of external ripening, delayed both colour break and CcGCC1 overexpression. [Conclusions]: In this work, the citrus fruit ripening mutants 39B3 and 39E7 have been characterized at the phenotypic, biochemical and transcriptomic level. A defective synthesis of the apocarotenoid β-citraurin has been proposed to cause the yellowish colour of fully ripe 39E7 flavedo. The analyses of the mutant transcriptomes revealed that colour change during peel ripening was strongly associated with a major mobilization of mineral elements and with other previously known metabolic and photosynthetic changes. The expression of CcGCC1 was associated with peel ripening since CcGCC1 down-regulation correlated with a delay in colour break induced by genetic, developmental and hormonal causes.Work was supported by grants AGL2007-65437-C04-01/AGR (Centro de Genómica) and AGL2009-11558 (L. Zacarías and M. J. Rodrigo) from the Ministerio de Educación y Ciencia of Spain.Peer reviewe

Characterization of hemizygous deletions in Citrus using array-Comparative Genomic Hybridization and microsynteny comparisons with the poplar genome

<p>Abstract</p> <p>Background</p> <p>Many fruit-tree species, including relevant <it>Citrus </it>spp varieties exhibit a reproductive biology that impairs breeding and strongly constrains genetic improvements. In citrus, juvenility increases the generation time while sexual sterility, inbreeding depression and self-incompatibility prevent the production of homozygous cultivars. Genomic technology may provide citrus researchers with a new set of tools to address these various restrictions. In this work, we report a valuable genomics-based protocol for the structural analysis of deletion mutations on an heterozygous background.</p> <p>Results</p> <p>Two independent fast neutron mutants of self-incompatible clementine (<it>Citrus clementina </it>Hort. Ex Tan. cv. Clemenules) were the subject of the study. Both mutants, named 39B3 and 39E7, were expected to carry DNA deletions in hemizygous dosage. Array-based Comparative Genomic Hybridization (array-CGH) using a <it>Citrus </it>cDNA microarray allowed the identification of underrepresented genes in these two mutants. Subsequent comparison of citrus deleted genes with annotated plant genomes, especially poplar, made possible to predict the presence of a large deletion in 39B3 of about 700 kb and at least two deletions of approximately 100 and 500 kb in 39E7. The deletion in 39B3 was further characterized by PCR on available <it>Citrus </it>BACs, which helped us to build a partial physical map of the deletion. Among the deleted genes, <it>ClpC</it>-like gene coding for a putative subunit of a multifunctional chloroplastic protease involved in the regulation of chlorophyll <it>b </it>synthesis was directly related to the mutated phenotype since the mutant showed a reduced chlorophyll <it>a</it>/<it>b </it>ratio in green tissues.</p> <p>Conclusion</p> <p>In this work, we report the use of array-CGH for the successful identification of genes included in a hemizygous deletion induced by fast neutron irradiation on <it>Citrus clementina</it>. The study of gene content and order into the 39B3 deletion also led to the unexpected conclusion that microsynteny and local gene colinearity in this species were higher with <it>Populus trichocarpa </it>than with the phylogenetically closer <it>Arabidopsis thaliana</it>. This work corroborates the potential of <it>Citrus </it>genomic resources to assist mutagenesis-based approaches for functional genetics, structural studies and comparative genomics, and hence to facilitate citrus variety improvement.</p

Prediction of components of the sporopollenin synthesis pathway in peach by genomic and expression analyses

Background: The outer cell wall of the pollen grain (exine) is an extremely resistant structure containing sporopollenin, a mixed polymer made up of fatty acids and phenolic compounds. The synthesis of sporopollenin in the tapetal cells and its proper deposition on the pollen surface are essential for the development of viable pollen. The beginning of microsporogenesis and pollen maturation in perennial plants from temperate climates, such as peach, is conditioned by the duration of flower bud dormancy. In order to identify putative genes involved in these processes, we analyzed the results of previous genomic experiments studying the dormancy-dependent gene expression in different peach cultivars. Results: The expression of 50 genes induced in flower buds after the endodormancy period (flower-bud late genes) was compared in ten cultivars of peach with different dormancy behaviour. We found two co-expression clusters enriched in putative orthologs of sporopollenin synthesis and deposition factors in Arabidopsis. Flower-bud late genes were transiently expressed in anthers coincidently with microsporogenesis and pollen maturation processes. We postulated the participation of some flower-bud late genes in the sporopollenin synthesis pathway and the transcriptional regulation of late anther development in peach. Conclusions: Peach and the model plant Arabidopsis thaliana show multiple elements in common within the essential sporopollenin synthesis pathway and gene expression regulatory mechanisms affecting anther development. The transcriptomic analysis of dormancy-released flower buds proved to be an efficient procedure for the identification of anther and pollen development genes in perennial plants showing seasonal dormancy

Búsqueda de interactores para la caracterización de los genes ParPMC implicados en la resistencia a Sharka en albaricoquero

La enfermedad de la Sharka, causada por el potyvirus Plum pox virus (PPV) es el factor más limitante para el cultivo de frutales de hueso. El desarrollo de variedades resistentes se ha propuesto como la mejor solución para el control de esta enfermedad. Sin embargo, se conocen pocas fuentes de resistencia que puedan ser de utilidad para su incorporación a los programas de mejora. En el caso de albaricoque se identificaron una decena de variedades norteamericanas que muestran resistencia a PPV. Combinando datos genéticos y genómicos propusimos a los genes ParPMC1 y ParPMC2 como genes de susceptibilidad cuyo silenciamiento confiere resistencia a PPV

Single-Bud Expression Analysis of Bud Dormancy Factors in Peach

Transcriptomic and gene expression analysis have greatly facilitated the identification and characterization of transcriptional regulatory factors and effectors involved in dormancy progression and other physiological processes orchestrated during bud development in peach and other temperate fruit species. Gene expression measurements are most usually based on average values from several or many individual buds. We have performed single-bud gene analysis in flower buds of peach across dormancy release using amplicons from the master regulatory DORMANCY-ASSOCIATED MADS-BOX (DAM) factors, several jasmonic acid biosynthetic genes, other genes related to flowering development, cell growth resumption, and abiotic stress tolerance. This analysis provides a close view on gene-specific, single-bud variability throughout the developmental shift from dormant to dormancy-released stages, contributing to the characterization of putative co-expression modules and other regulatory aspects in this particular tissue

Editorial: New insights into mechanisms of epigenetic modifiers in plant growth and development, volume II

As we have learned, chromatin modifications, including histone modifications and DNA methylation, play a key role in plant development (Ng and Bird, 1999). However, accumulated evidence shows that, besides chromatin biochemical modifications, other epigenetic regulations such as chromatin architecture also function at a pivot point to regulate plant development (Zhang et al., 2021). In this Research Topic, five research papers describe multiple developmental facets mediated by different epigenetic mechanisms besides histone modifications. These manuscripts report experimental evidence or summarize recent advances in epigenetic regulations of some important developmental genes or development-related mechanisms. This Research Topic allows readers to learn of the latest advances in epigenetic regulations on seed germination, flowering time control, miRNA biogenesis and stability, secondary meristem maintenance as well as histone deacetylase 9 mediated day-length dependent hypocotyl cell elongation

Evaluación de patrones y variedades no astringentes de caqui frente a los retos de sostenibilidad y cambio climático en la Comunidad Valenciana

En los últimos años, el cultivo del caqui ha crecido extraordinariamente en la Comunidad Valenciana (CV) debido a la alta calidad de la variedad ‘Rojo Brillante’, y a la puesta a punto del procedimiento para la eliminación de la astringencia de los frutos sin pérdida de la firmeza. Sin embargo, la dependencia de esta variedad hace que la producción se concentre en unas fechas determinadas, y que la aparición de enfermedades y las alteraciones debidas al cambio climático supongan un desafío todavía mayor para este cultivo en los próximos años

Engineering Tree Seasonal Cycles of Growth Through Chromatin Modification

In temperate and boreal regions, perennial trees arrest cell division in their meristematic tissues during winter dormancy until environmental conditions become appropriate for their renewed growth. Release from the dormant state requires exposure to a period of chilling temperatures similar to the vernalization required for flowering in Arabidopsis. Over the past decade, genomic DNA (gDNA) methylation and transcriptome studies have revealed signatures of chromatin regulation during active growth and winter dormancy. To date, only a few chromatin modification genes, as candidate regulators of these developmental stages, have been functionally characterized in trees. In this work, we summarize the major findings of the chromatin-remodeling role during growth-dormancy cycles and we explore the transcriptional profiling of vegetative apical bud and stem tissues during dormancy. Finally, we discuss genetic strategies designed to improve the growth and quality of forest trees