The mathematics of sexual attraction

Pollen tubes follow attractants secreted by the ovules. In a recent paper in BMC Plant Biology, Stewman and colleagues have quantified the parameters of this attraction and used them to calibrate a mathematical model that reproduces the process and enables predictions on the nature of the female attractant and the mechanisms of the male response

A Transcriptome Atlas of Physcomitrella patens Provides Insights into the Evolution and Development of Land Plants

Post-print version of the article.Identifying the genetic mechanisms that underpin the evolution of new organ and tissue systems is an aim of evolutionary developmental biology. Comparative functional genetic studies between angiosperms and bryophytes can define those genetic changes that were responsible for developmental innovations. Here, we report the generation of a transcriptome atlas covering most phases in the life cycle of the model bryophyte Physcomitrella patens, including detailed sporophyte developmental progression. We identified a comprehensive set of sporophyte-specific transcription factors, and found that many of these genes have homologs in angiosperms that function in developmental processes such as flowering and shoot branching. Deletion of the PpTCP5 transcription factor results in development of supernumerary sporangia attached to a single seta, suggesting that it negatively regulates branching in the moss sporophyte. Given that TCP genes repress branching in angiosperms, we suggest that this activity is ancient. Finally, comparison of P. patens and Arabidopsis thaliana transcriptomes led us to the identification of a conserved core of transcription factors expressed in tip-growing cells. We identified modifications in the expression patterns of these genes that could account for developmental differences between P. patens tip-growing cells and A. thaliana pollen tubes and root hairs.ERA-NET: (2nd call ERA-NET for Coordinating Plant Sciences); Fundação para a Ciência e a Tecnologia

GABA signalling modulates plant growth by directly regulating the activity of plant-specific anion transporters

The non-protein amino acid, gamma-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to biotic and abiotic stress, and regulates plant growth. Until now it was not known whether GABA exerts its effects in plants through the regulation of carbon metabolism or via an unidentified signalling pathway. Here, we demonstrate that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA. Site-directed mutagenesis of selected amino acids within ALMT proteins abolishes GABA efficacy but does not alter other transport properties. GABA modulation of ALMT activity results in altered root growth and altered root tolerance to alkaline pH, acid pH and aluminium ions. We propose that GABA exerts its multiple physiological effects in plants via ALMT, including the regulation of pollen tube and root growth, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms.Australian Research Council; Waite Research Institute grants: (FT130100709, DP130104205, CE140100008); Fundação para a Ciência e Tecnologia grant: (PTDC/BEX-BCM/0376/2012); University of Maryland.info:eu-repo/semantics/publishedVersio

Avaliação da aterosclerose subclínica e de níveis plasmáticos de LDL minimamente modificada em pacientes com espondilite anquilosante e sua correlação com a atividade da doença

AbstractIntroductionAccelerated atherosclerosis has been shown in some autoimmune diseases, mainly in Systemic Lupus Erythematosus and Rheumatoid Arthritis. Although high preva- lence of corticosteroids use may be a confounding factor due to their detrimental effects on several risk factors, systemic inflammation per se is supposed to play an important role in atherogenesis in these patients.MethodsWe have evaluated sub-clinical atherosclerosis and plasma levels of circulating electronegative LDL, which represents the fraction of LDL that is minimally modified, in patients with ankylosing spondylitis (AS). Fourteen patients who fulfilled the modified New York criteria for AS were compared with 13 paired controls. Carotid intimal-media thick- ness (IMT) was assessed by ultrasonography bilaterally in common carotid artery, internal carotid artery and in the bifurcation. Groups were homogeneous regarding cardiovascular risk factors. Only a single patient in AS group was in use of corticosteroid.ResultsThe presence of active inflammation was demonstrated by elevated BASDAI and higher CRP levels and in patients versus controls (12.36 vs. 3.45mg/dl, P = 0.002). No dif- ference was found in carotid IMT between both groups, in any site of artery. Averaged IMT (6 measurements, at 3 pre-specified sites bilaterally) was 0.72 ± 0.28 in AS group and 0.70 ± 0.45mm in controls (P = 0.91). Minimally modified LDL did not differ significantly either between patients and controls (14.03 ± 17.40 vs. 13.21 ± 10.21; P = 0.88).ConclusionsPatients with AS did not show increased carotid IMT in comparison to con- trols. In the same way, circulating plasma levels of LDL (-), did not differ significantly in both groups

Glutamate receptor-like channels are essential for chemotaxis and reproduction in mosses

The deposited article version is a "Accelerated Article Preview" provided by Nature Publishing Group, and it contains attached the supplementary materials within the pdf.». This publication hasn't any creative commons license associated.Glutamate receptors are well characterized channels that mediate cell-to-cell communication during neurotransmission in animals. Nevertheless, information regarding their functional role in organisms without nervous systems is still limited. In plants, Glutamate Receptor-like (GLR) genes have been implicated in defence against pathogens, reproduction, control of stomata aperture and light signal transduction(1-5). However, the numerous GLR genes present in angiosperm genomes (20 to 70)(6) has prevented the observation of strong phenotypes in loss-of-function mutants. Here, we show that in the moss Physcomitrella patens, a basal land plant, mutation of GLR genes cause sperm failure in targeting the female reproductive organs. In addition, we show that GLR genes encode non-selective Ca(2+) permeable channels that can regulate cytoplasmic Ca(2+) and are needed to induce the expression of a BELL1-like transcription factor essential for zygote development. Our work reveals novel functions for GLRs in sperm chemotaxis and transcriptional regulation. Sperm chemotaxis is essential for fertilization in both animals and early land plants like bryophytes and pteridophytes. Therefore, our results are suggestive that ionotropic glutamate receptors may have been conserved throughout plant evolution to mediate cell-to-cell communication during sexual reproduction.Phillips University; Oxford University; University of Marburg; University of Muenster; MarieCurie ITN-Plant Origins grant: (FP7-PEOPLE-ITN-2008); FCT grants: (BEX-BCM/0376/2012; PTDC/BIA-PLA/4018/2012); NSF-US grant: (MCB 1616437/2016).info:eu-repo/semantics/acceptedVersio

The scope of language contact as a constraint factor in language change: The periphrasis haber de plus infinitive in a corpus of language immediacy in modern Spanish

In this work an empirical study grounded in the principles and methods of the comparative variationist framework is conducted to measure the scope of language contact as a factor constraining some potentially diverging uses of a Spanish verbal periphrasis that has undergone a sharp decline over the last century (haber de plus infinitive). The analysis is based on three independent samples of text that correspond to three dialectal areas of peninsular Spanish (monolingual zones, Catalan-speaking linguistic territories and the north-western linguistic area). These samples, extracted from a corpus made up of texts of communicative immediacy from the 19th and the first half of the 20th centuries, confirm the existence of a certain linguistic convergence in the expressive habits of the speakers in the bilingual communities. In each region, however, the outcomes are different, due to parallel differences in the structural position of the periphrasis in each language. However, a thorough analysis of the variable context that surrounds the periphrasis shows that the observed differences do not affect the essence of the underlying grammar of this variant, whose decline (which favours tener que plus infinitive and becomes faster as the 20th century advances) is constrained by identical linguistic and extralinguistic conditioning factors in all the dialectal areas

The calcium-permeable channel OSCA1.3 regulates plant stomatal immunity

Perception of biotic and abiotic stresses often leads to stomatal closure in plants 1,2. Rapid influx of calcium ions (Ca 2+) across the plasma membrane has an important role in this response, but the identity of the Ca 2+ channels involved has remained elusive 3,4. Here we report that the Arabidopsis thaliana Ca 2+-permeable channel OSCA1.3 controls stomatal closure during immune signalling. OSCA1.3 is rapidly phosphorylated upon perception of pathogen-associated molecular patterns (PAMPs). Biochemical and quantitative phosphoproteomics analyses reveal that the immune receptor-associated cytosolic kinase BIK1 interacts with and phosphorylates the N-terminal cytosolic loop of OSCA1.3 within minutes of treatment with the peptidic PAMP flg22, which is derived from bacterial flagellin. Genetic and electrophysiological data reveal that OSCA1.3 is permeable to Ca 2+, and that BIK1-mediated phosphorylation on its N terminus increases this channel activity. Notably, OSCA1.3 and its phosphorylation by BIK1 are critical for stomatal closure during immune signalling, and OSCA1.3 does not regulate stomatal closure upon perception of abscisic acid—a plant hormone associated with abiotic stresses. This study thus identifies a plant Ca 2+ channel and its activation mechanisms underlying stomatal closure during immune signalling, and suggests specificity in Ca 2+ influx mechanisms in response to different stresses