La planta model Arabidopsis thaliana

En els últims trenta anys la planta angiosperma Arabidopsis thaliana ha estat l'organisme model utilitzat per milers de biòlegs. Arabidopsis s'autopol·linitza, té un genoma petit, té un cicle de vida curt, és de mida petita i té uns requisits de creixement senzills que la fan fàcil de fer créixer en condicions de laboratori. L'èxit d'Arabidopsis com a planta model es basa en la disponibilitat de mètodes genòmics i d'eines que han estimulat la recerca en la biologia de plantes i han facilitat la investigació d'un ampli ventall de preguntes biològiques. Aquest article explica alguns dels esdeveniments clau en la història d'Arabidopsis com a planta model, i en el creixement de la comunitat d'investigadors que la utilitzen per a la seva recerca. I també il·lustra com Arabidopsis ha facilitat la recerca, amb l'exemple en un camp d'especial interès en plantes: el de la percepció i resposta a la llum del seu entorn.The model plant Arabidopsis thaliana. During the past 30 years, the flowering plant Arabidopsis thaliana has been the model organism of choice for thousands of biologists. Arabidopsis is self-fertilizing, has a small genome, has a short life cycle, and the small size and simple growth requirements make it easy to grow in laboratory conditions. The extensive acceptance of Arabidopsis as a model plant is based on the genomic methods and resources that are available for it, which have greatly stimulated plant biological research and have facilitated the investigation of a range of biological questions. Here, we review some of the key events in the history of Arabidopsis as a model plant and the growth of the Arabidopsis research community. And we explain how Arabidopsis has facilitated the research in a field of particular importance in plants: the perception and response to their light environment

Red and blue light differentially impact retrograde signalling and photoprotection in rice

Chloroplast-to-nucleus retrograde signalling (RS) is known to impact plant growth and development. In Arabidopsis, we and others have shown that RS affects seedling establishment by inhibiting deetiolation. In the presence of lincomycin, a chloroplast protein synthesis inhibitor that triggers RS, Arabidopsis light-grown seedlings display partial skotomorphogenesis with undeveloped plastids and closed cotyledons. By contrast, RS in monocotyledonous has been much less studied. Here, we show that emerging rice seedlings exposed to lincomycin do not accumulate chlorophyll but otherwise remain remarkably unaffected. However, by using high red (R) and blue (B) monochromatic lights in combination with lincomycin, we have uncovered a RS inhibition of length and a reduction in the B light-induced declination of the second leaf. Furthermore, we present data showing that seedlings grown in high B and R light display different non-photochemical quenching capacity. Our findings support the view that excess B and R light impact seedling photomorphogenesis differently to photoprotect and optimize the response to high-light stres

PIF1 promotes phytochrome-regulated growth under photoperiodic conditions in Arabidopsis together with PIF3, PIF4, and PIF5

Seedlings growing under diurnal conditions display maximal growth at the end of the night in short-day (SD) photoperiods. Current evidence indicates that this behaviour involves the action of PHYTOCHROME-INTERACTING FACTOR 3 (PIF3) together with PIF4 and PIF5, through direct regulation of growth-related genes at dawn coinciding with a PIF3 accumulation peak generated by phytochrome-imposed oscillations in protein abundance. Here, to assess how alterations in PIF3 levels impact seedling growth, the night-specific accumulation of PIF3 was modulated by releasing SD-grown seedlings into continuous light, or by exposing them to a phytochrome-inactivating end-of-day far-red pulse (EOD-FRp). The data show a strong direct correlation between PIF3 accumulation, PIF3-regulated induction of growth-related genes, and hypocotyl elongation, and suggest that growth promotion in SD conditions involves factors other than PIF3, PIF4, and PIF5. Using a pif1 mutant, evidence is provided that PIF1 also contributes to inducing hypocotyl elongation during the dark period under diurnal conditions. PIF1 displayed constitutive transcript levels in SD conditions, suggesting that phytochrome-imposed oscillations in PIF1 protein abundance determine its accumulation and action during the night, similar to PIF3 and in contrast to PIF4 and PIF5, which oscillate diurnally due to a combination of circadian clock-regulated transcription and light control of protein accumulation. Furthermore, using single and higher order pif mutants, the relative contribution of each member of the PIF quartet to the regulation of morphogenesis and the expression of selected growth marker genes under SD conditions, or under SD conditions supplemented with an EOD-FRp, is defined. Collectively, the data indicate that PIF1, PIF3, PIF4, and PIF5 act together to promote and optimize growth under photoperiodic conditions

D5.7-Policy Paper 2. Recommendations on policies to promote mutual understanding between refugees and the local communities in Europe

The deliverable develops the WP2 activities' findings into recommendations for policy makers, in order to enhance social cohesion, mutual undertanding and efeective integration between local communities and refugee / asylum seeker individuals and communities in terms of cultural heritage and historical and personal memories

The photoperiodic response of hypocotyl elongation involves regulation of CDF1 and CDF5 activity

Hypocotyl elongation relies on directional cell expansion, a process under light and circadian clock control. Under short photoperiods (SD), hypocotyl elongation in Arabidopsis thaliana follows a rhythmic pattern, a process in which circadian morning-to-midnight waves of the transcriptional repressors PSEUDO-RESPONSE REGULATORS (PRRs) jointly gate PHYTOCHROME-INTERACTING FACTOR (PIF) activity to dawn. Previously, we described CYCLING DOF FACTOR 5 (CDF5) as a target of this antagonistic PRR/PIF dynamic interplay. Under SD, PIFs induce CDF5 accumulation specifically at dawn, when it promotes the expression of positive cell elongation regulators such as YUCCA8 to induce growth. In contrast to SD, hypocotyl elongation under long days (LD) is largely reduced. Here, we examine whether CDF5 is an actor in this photoperiod specific regulation. We report that transcription of CDF5 is robustly induced in SD compared to LD, in accordance with PIFs accumulating to higher levels in SD, and in contrast to other members of the CDF family, whose expression is mainly clock regulated and have similar waveforms in SD and LD. Notably, when CDF5 was constitutively expressed under LD, CDF5 protein accumulated to levels comparable to SD but was inactive in promoting cell elongation. Similar results were observed for CDF1. Our findings indicate that both CDFs can promote cell elongation specifically in shorter photoperiods, however, their activity in LD is inhibited at the post-translational level. These data not only expand our understanding of the biological role of CDF transcription factors, but also identify a previously unrecognized regulatory layer in the photoperiodic response of hypocotyl elongation

Hepatitis C virus co-infection and sexual risk behaviour are associated with a high homocysteine serum level in HIV-infected patients

BACKGROUND AND AIMS: A better understanding of the relationship of homocysteine with cardiovascular risk factors is needed. The objectives of this study were to assess the serum level of homocysteine in HIV-infected patients and to analyse the possible association of increased levels of the amino acid with cardiovascular risk factors, demographic and clinical characteristics of participants. METHODS: Cross-sectional study carried out as a supplementary task to the usual controls necessary in HIV-infected patients in the outpatient clinic of the Hospital General of Castellon, Spain. For two consecutive visits the demographic, clinical and HIV-related characteristics and blood analyses results were obtained for each participant. Homocysteine serum level was documented and the possible association of the amino acid with all the other study variables was assessed with a multiple linear regression analysis. RESULTS: A total of 145 patients were included. The mean homocysteine serum level of all participants was 11.9 ± 5.9 µmol/L. A total of 54 patients (37%) presented homocysteine serum levels higher than the upper limit of normal. An association was found between higher homocysteine serum level and the following variables: family history of early coronary disease (P = 0.027), sexual HIV risk behaviour (P = 0.016), hepatitis C virus co-infection (P = 0.002), higher height (P = 0.002), higher diastolic blood pressure (P = 0.049), lower serum level of folic acid (P <0.001), and lower serum level of vitamin B12 (P = <0.001). CONCLUSION: In the HIV population, increased homocysteine serum level is associated with sexual risk behaviour and hepatitis C virus coinfection

Negative multiparametric magnetic resonance imaging for prostate cancer: what's next?

Multiparametric magnetic resonance imaging (mpMRI) of the prostate has excellent sensitivity in detecting clinically significant prostate cancer (csPCa). Nevertheless, the clinical utility of negative mpMRI (nMRI) is less clearMultiparametric magnetic resonance imaging (mpMRI) of the prostate has excellent sensitivity in detecting clinically significant prostate cancer (csPCa). Nevertheless, the clinical utility of negative mpMRI (nMRI) is less clear. OBJECTIVE: To assess outcomes of men with nMRI and clinical follow-up after 7 yr of activity at a reference center. DESIGN, SETTING, AND PARTICIPANTS: All mpMRI performed from January 2010 to May 2015 were reviewed. We selected all patients with nMRI and divided them in group A (naïve patients) and group B (previous negative biopsy). All patients without a diagnosis of PCa had a minimum follow-up of 2 yr and at least two consecutive nMRI. Patients with positive mpMRI were also identified to assess their biopsy outcomes. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: A Kaplan-Meier analysis was performed to assess both any-grade PCa and csPCa diagnosis-free survival probabilities. Univariable and multivariable Cox regression models were fitted to identify predictors of csPCa diagnosis. RESULTS AND LIMITATIONS: We identified 1545 men with nMRI, and 1255 of them satisfied the inclusion criteria; 659 belonged to group A and 596 to group B. Any-grade PCa and csPCa diagnosis-free survival probabilities after 2 yr of follow-up were 94% and 95%, respectively, in group A; in group B, they were 96%. After 48 mo of follow-up, any-grade PCa diagnosis-free survival probability was 84% in group A and 96% in group B (log rank p&lt;0.001). Diagnosis-free survival probability for csPCa was unchanged after 48 mo of follow-up. On multivariable Cox regression analysis, increasing age (p=0.005) was an independent predictor of lower csPCa diagnosis probability, while increasing prostate-specific antigen (PSA) and PSA density (&lt;0.001) independently predicted higher csPCa diagnosis probability. The prevalence of and positive predictive value for csPCa were 31.6% and 45.5%, respectively. Limitations include limited follow-up and the inability to calculate true csPCa prevalence in the study population. CONCLUSIONS: mpMRI is highly reliable to exclude csPCa. Nevertheless, systematic biopsy should be recommended even after nMRI, especially in younger patients with high or raising PSA levels

Phytochrome-imposed inhibition of PIF7 activity shapes photoperiodic growth in Arabidopsis together with PIF1 , 3, 4 and 5

Under photoperiodic conditions, Arabidopsis thaliana seedling growth is inhibited in long days (LDs), but promoted under the extended nights of short days (SDs). This behavior is partly implemented by phytochrome (phy)-imposed oscillations in the abundance of the growth-promoting, phy-interacting bHLH transcription factors PHY-INTERACTING FACTOR 1 (PIF1), PIF3, PIF4 and PIF5 (PIF quartet or PIFq). However, the observation that a pifq mutant is still stimulated to elongate when given a phy-inactivating end-of-day far-red pulse (EODFR), suggests that additional factors are involved in the phy-mediated suppression of growth during the subsequent dark period. Here, by combining growth-analysis of pif7 single- and higher-order mutants with gene expression analysis under SD, LD, SD-EODFR, and LD-EODFR, we show that PIF7 promotes growth during the dark hours of SD, by regulating growth-related gene expression. Interestingly, the relative contribution of PIF7 in promoting growth is stronger under EODFR, whereas PIF3 role is more important under SD, suggesting that PIF7 is a prominent target of phy-suppression. Indeed, we show that phy imposes phosphorylation and inactivation of PIF7 during the light hours in SD, and prevents full dephosphorylation during the night. This repression can be lifted with an EODFR, which correlates with increased PIF7-mediated gene expression and elongation. In addition, our results suggest that PIF7 function might involve heterodimerization with PIF3. Furthermore, our data indicate that a pifqpif7 quintuple mutant is largely insensitive to photoperiod for hypocotyl elongation. Collectively, the data suggest that PIF7, together with the PIFq, is required for the photoperiodic regulation of seasonal growth

Seedling establishment : a a dimmer switch-regulated process between dark and light signaling

By being exquisitely sensitive to their light surroundings, plants are able to continuously adjust their growth to optimize fitness. Darkness is an important cue for plants and a time when they actively grow and develop through regulation of the appropriate gene networks and biochemical changes. Although plants might not possess "dark receptors," inactive photoreceptors facilitate activation and inhibition of dark-specific processes, and thus darkness itself might be considered a signal triggering a myriad of responses. In this Update, we review the effects of dark and light signaling during seedling establishment. We describe the features of seedlings germinated in the dark and their switch in development upon emerging into the light. We examine how aboveground growth is regulated by the duration of dark/light cycles and how circadian clock signaling is integrated. Finally, we discuss some of the challenges faced by young seedlings during their establishment, such as variations in temperature or in light quality and quantity. Although mentioned briefly, we do not cover in detail the contribution of sugars or temperature to seedling establishment in response to dark and light signals; we refer readers to excellent recent reviews (Franklin et al., 2014; Legris et al., 2017; Seluzicki et al., 2017). The emerging view is that of seedling establishment regulated as a dimmer-type switch where relative amounts of dark and light signaling dynamically optimize plant development to the surrounding light environment