FM-dyes as experimental probes for dissecting vesicle trafficking in living plant cells

FM-dyes are widely used to study endocytosis, vesicle trafficking and organelle organization in living eukaryotic cells. The increasing use of FM-dyes in plant cells has provoked much debate with regard to their suitability as endocytosis markers, which organelles they stain and the precise pathways they follow through the vesicle trafficking network. A primary aim of this article is to assess critically the current status of this debate in plant cells. For this purpose, background information on the important characteristics of the FM-dyes, and of optimal dye concentrations, conditions of dye storage, and staining and imaging protocols, are provided. Particular emphasis is placed on using the FM-dyes in double labelling experiments to identity specific organelles. In this way, staining of the Golgi with FM4-64 has been demonstrated for the first time

Cell and plastid division are coordinated through the prereplication factor AtCDT1

The cell division cycle involves nuclear and cytoplasmic events, namely organelle multiplication and distribution between the daughter cells. Until now, plastid and plant cell division have been considered as independent processes because they can be uncoupled. Here, down-regulation of AtCDT1a and AtCDT1b, members of the prereplication complex, is shown to alter both nuclear DNA replication and plastid division in Arabidopsis thaliana. These data constitute molecular evidence for relationships between the cell-cycle and plastid division. Moreover, the severe developmental defects observed in AtCDT1-RNA interference (RNAi) plants underline the importance of coordinated cell and organelle division for plant growth and morphogenesis

Eukaryotic control on bacterial cell cycle and differentiation in the Rhizobium–legume symbiosis

Symbiosis between legumes and Rhizobium bacteria leads to the formation of root nodules where bacteria in the infected plant cells are converted into nitrogen-fixing bacteroids. Nodules with a persistent meristem are indeterminate, whereas nodules without meristem are determinate. The symbiotic plant cells in both nodule types are polyploid because of several cycles of endoreduplication (genome replication without mitosis and cytokinesis) and grow consequently to extreme sizes. Here we demonstrate that differentiation of bacteroids in indeterminate nodules of Medicago and related legumes from the galegoid clade shows remarkable similarity to host cell differentiation. During bacteroid maturation, repeated DNA replication without cytokinesis results in extensive amplification of the entire bacterial genome and elongation of bacteria. This finding reveals a positive correlation in prokaryotes between DNA content and cell size, similar to that in eukaryotes. These polyploid bacteroids are metabolically functional but display increased membrane permeability and are nonviable, because they lose their ability to resume growth. In contrast, bacteroids in determinate nodules of the nongalegoid legumes lotus and bean are comparable to free-living bacteria in their genomic DNA content, cell size, and viability. Using recombinant Rhizobium strains nodulating both legume types, we show that bacteroid differentiation is controlled by the host plant. Plant factors present in nodules of galegoid legumes but absent from nodules of nongalegoid legumes block bacterial cell division and trigger endoreduplication cycles, thereby forcing the endosymbionts toward a terminally differentiated state. Hence, Medicago and related legumes have evolved a mechanism to dominate the symbiosis

Physical mapping of ribosomal DNA and genome size in diploid and polyploid North African Calligonum species (Polygonaceae)

38 p., tablas, gráf.Most Calligonum species are desert plants, characteristic of the Saharan bioclimatic region. All species karyologically analyzed until present have the basic chromosome number x = 9 and comprise diploids, triploids and tetraploids. The Tunisian flora comprises diploid Calligonum arich and C. azel, of restricted distribution, and the tetraploid C. comosum with wider distribution. Analyses of their karyotypes and polyploidisation-linked rDNA changes by orcein staining, fluorochrome banding with chromomycin A3 and fluorescent in situ hybridisation with 5S and 26S ribosomal DNA probes have been performed. We report the chromosome number for Calligonum arich (2n = 18) as well as the diploid level for C. comosum for the first time. Chromosome counts have also verified the earlier described tetraploid cytotype (2n = 36) of C. comosum. A general pattern of six GC-rich bands as well as two 35S sites and four 5S sites is described for Calligonum species at the diploid level although there is intraspecific variation regarding the site number in a second type of C. comosum, with one pair of 35S rDNA sites and two pairs of 5S rDNA sites. The tetraploid cytotype of C. comosum has undergone locus loss and genome downsizing. Genome size assessments confirmed previous data. Nonetheless, statistically significant differences were found depending on the type of tissue used for estimation. Measurements from seeds had always larger values than from leaves. The presence of cytosolic compounds in leaves, interfering with DNA staining, is discussed as a possible cause of the differences.This work was supported by the Dirección General de Investigación Científica y Técnica, government of Spain (CGL2010-22234-C02-01/BOS and CGL2010-22234-C02-02/BOS) and the Generalitat de Catalunya, government of Catalonia (‘‘Ajuts a grups de recerca consolidats’’, 2009SGR0439). SG and OH benefitted from Juan de la Cierva postdoctoral contracts of the Ministry of Economy and Competitiveness, government of Spain.Peer reviewe

Reinventar la izquierda en el siglo XXI : hacia un diálogo norte-sur

Una sugerente ambigüedad habita el título de este libro, en el que el verbo reinventar parece tener al mismo tiempo dos valores diferentes. Uno descriptivo: el de nombrar lo que un conjunto de experiencias políticas recientes ha hecho o viene haciendo (sobre todo aquí, en la América Latina posterior al estallido del orden neoliberal que, con diversas variantes y matices, había dominado toda la región durante el último cuarto del siglo pasado) con las tradiciones políticas que solemos nombrar con la palabra izquierda. Y otro prescriptivo: el de indicar lo que sería conveniente o necesario hacer con esas tradiciones, o a partir de esas tradiciones, para ponerlas a la altura (aquí y por todos lados, aunque en primer lugar, claro, en la vieja Europa donde la propia idea de izquierda inició hace algo más de dos siglos su jornada) de los desafíos de los nuevos tiempos. Este libro es una herramienta decisiva para una discusión indispensable, que tiene el mérito adicional de ser el resultado de una conversación entre expertos del Norte y del Sur del mundo dispuestos a intentar entender y explicar la especificidad de sus propias situaciones y a ensanchar esa mirada con las perspectivas que les llegan desde el otro extremo del planeta

The genome sequence of the grape phylloxera provides insights into the evolution, adaptation, and invasion routes of an iconic pest (vol 18, 90, 2020)

An amendment to this paper has been published and can be accessed via the original article

The sunflower genome provides insights into oil metabolism, flowering and Asterid evolution

The domesticated sunflower, Helianthus annuus L., is a global oil crop that has promise for climate change adaptation, because it can maintain stable yields across a wide variety of environmental conditions, including drought. Even greater resilience is achievable through the mining of resistance alleles from compatible wild sunflower relatives, including numerous extremophile species. Here we report a high-quality reference for the sunflower genome (3.6 gigabases), together with extensive transcriptomic data from vegetative and floral organs. The genome mostly consists of highly similar, related sequences and required single-molecule real-time sequencing technologies for successful assembly. Genome analyses enabled the reconstruction of the evolutionary history of the Asterids, further establishing the existence of a whole-genome triplication at the base of the Asterids II clade and a sunflower-specific whole-genome duplication around 29 million years ago. An integrative approach combining quantitative genetics, expression and diversity data permitted development of comprehensive gene networks for two major breeding traits, flowering time and oil metabolism, and revealed new candidate genes in these networks. We found that the genomic architecture of flowering time has been shaped by the most recent whole-genome duplication, which suggests that ancient paralogues can remain in the same regulatory networks for dozens of millions of years. This genome represents a cornerstone for future research programs aiming to exploit genetic diversity to improve biotic and abiotic stress resistance and oil production, while also considering agricultural constraints and human nutritional needs