Interplay of Sugar, Light and Gibberellins in Expression of Rosa hybrida Vacuolar Invertase 1 Regulation

Our previous findings showed that the expression of the Rosa hybrida vacuolar invertase 1 gene (RhVI1) was tightly correlated with the ability of buds to grow out and was under sugar, gibberellin and light control. Here, we aimed to provide an insight into the mechanistic basis of this regulation. In situ hybridization showed that RhVI1 expression was localized in epidermal cells of young leaves of bursting buds. We then isolated a 895 bp fragment of the promoter of RhVI1. In silico analysis identified putative cis-elements involved in the response to sugars, light and gibberellins on its proximal part (595 bp). To carry out functional analysis of the RhVI1 promoter in a homologous system, we developed a direct method for stable transformation of rose cells. 5′ deletions of the proximal promoter fused to the uidA reporter gene were inserted into the rose cell genome to study the cell’s response to exogenous and endogenous stimuli. Deletion analysis revealed that the 468 bp promoter fragment is sufficient to trigger reporter gene activity in response to light, sugars and gibberellins. This region confers sucrose- and fructose-, but not glucose-, responsive activation in the dark. Inversely, the –595 to –468 bp region that carries the sugar-repressive element (SRE) is required to down-regulate the RhVI1 promoter in response to sucrose and fructose in the dark. We also demonstrate that sugar/light and gibberellin/light act synergistically to up-regulate β-glucuronidase (GUS) activity sharply under the control of the 595 bp pRhVI1 region. These results reveal that the 127 bp promoter fragment located between –595 and –468 bp is critical for light and sugar and light and gibberellins to act synergistically

Insight into the Role of Sugars in Bud Burst Under Light in the Rose

Bud burst is a decisive process in plant architecture that requires light in Rosa sp. This light effect was correlated with stimulation of sugar transport and metabolism in favor of bud outgrowth. We investigated whether sugars could act as signaling entities in the light-mediated regulation of vacuolar invertases and bud burst. Full-length cDNAs encoding two vacuolar invertases (RhVI1 and RhVI2) were isolated from buds. Unlike RhVI2, RhVI1 was preferentially expressed in bursting buds, and was up-regulated in buds of beheaded plants exposed to light. To assess the importance of sugars in this process, the expression of RhVI1 and RhVI2 and the total vacuolar invertase activity were further characterized in buds cultured in vitro on 100 mM sucrose or mannitol under light or in darkness for 48 h. Unlike mannitol, sucrose promoted the stimulatory effect of light on both RhVI1 expression and vacuolar invertase activity. This up-regulation of RhVI1 was rapid (after 6 h incubation) and was induced by as little as 10 mM sucrose or fructose. No effect of glucose was found. Interestingly, both 30 mM palatinose (a non-metabolizable sucrose analog) and 5 mM psicose (a non-metabolizable fructose analog) promoted the light-induced expression of RhVI1 and total vacuolar invertase activity. Sucrose, fructose, palatinose and psicose all promoted bursting of in vitro cultured buds under light. These findings indicate that soluble sugars contribute to the light effect on bud burst and vacuolar invertases, and can function as signaling entities

Regulation of flavonoid biosynthesis involves an unexpected complex transcriptional regulation of TT8 expression, in Arabidopsis

TT8/bHLH042 is a key regulator of anthocyanins and proanthocyanidins (PAs) biosynthesis in Arabidopsis thaliana. TT8 transcriptional activity has been studied extensively, and relies on its ability to form, with several R2R3-MYB and TTG1 (WD-Repeat protein), different MYB-bHLH-WDR (MBW) protein complexes. By contrast, little is known on how TT8 expression is itself regulated.Transcriptional regulation of TT8 expression was studied using molecular, genetic and biochemical approaches. Functional dissection of the TT8 promoter revealed its modular structure. Two modules were found to specifically drive TT8 promoter activity in PA- and anthocyanin-accumulating cells, by differentially integrating the signals issued from different regulators, in a spatio-temporal manner. Interestingly, this regulation involves at least six different MBW complexes, and an unpredicted positive feedback regulatory loop between TT8 and TTG2. Moreover, the results suggest that some putative new regulators remain to be discovered. Finally, specific cis-regulatory elements through which TT8 expression is regulated were identified and characterized. Together, these results provide a molecular model consistent with the specific and highly regulated expression of TT8. They shed new light into the transcriptional regulation of flavonoid biosynthesis and provide new clues and tools for further investigation in Arabidopsis and other plant species

Phenotypic differences between dermal fibroblasts from different body sites determine their responses to tension and TGFβ1

BACKGROUND: Wounds in the nonglabrous skin of keloid-prone individuals tend to cause large disordered accumulations of collagen which extend beyond the original margins of the wound. In addition to abnormalities in keloid fibroblasts, comparison of dermal fibroblasts derived from nonwounded glabrous or nonglabrous skin revealed differences that may account for the observed location of keloids. METHODS: Fibroblast apoptosis and the cellular content of α-smooth-muscle actin, TGFβ1 receptorII and ED-A fibronectin were estimated by FACS analysis. The effects of TGFβ1 and serum were examined. RESULTS: In monolayer cultures non-glabrous fibroblasts were slower growing, had higher granularity and accumulated more α-smooth-muscle actin than fibroblasts from glabrous tissues. Keloid fibroblasts had the highest level of α-smooth-muscle actin in parallel with their expression level of ED-A fibronectin. TGFβ1 positively regulated α-smooth-muscle actin expression in all fibroblast cultures, although its effects on apoptosis in fibroblasts from glabrous and non-glabrous tissues were found to differ. The presence of collagen I in the ECM resulted in reduction of α-smooth-muscle actin. A considerable percentage of the apoptotic fibroblasts in attached gels were α-smooth-muscle actin positive. The extent of apoptosis correlated positively with increased cell and matrix relaxation. TGFβ1 was unable to overcome this apoptotic effect of matrix relaxation. CONCLUSION: The presence of myofibroblasts and the apoptosis level can be regulated by both TGFβ1 and by the extracellular matrix. However, reduction of tension in the matrix is the critical determinant. This predicts that the tension in the wound bed determines the type of scar at different body sites

Female preference for a male sexual trait uncorrelated with male body size in the Palmate newt (Triturus helveticus)

Mate choice is often based on the assessment of multiple traits. Depending on whether traits provide redundant or different information about male characteristics, correlation between traits is expected to arise or not. In species where size increases with age, body size can be a reliable indicator of adult survival whereas secondary sexual traits advertise other qualities like the ability to exploit local resources. However, because of correlations between morphological traits it is often difficult to determine whether females base their preference on the absolute or the relative size of secondary sexual traits. We addressed this issue in the palmate newt, Triturus helveticus. We selected the two most variable traits, body size and filament length, whose weak correlation suggested that they could signal different aspects of male condition or quality. We tested female preference for both traits in two experiments in which we controlled either for body size or filament length. Females preferred males with long filament in experiment 1 and males with small body sizes in experiment 2. The preference for an exaggerated trait like the caudal filament is not unexpected in a context of inter-sexual selection. In contrast, the preference for small males contrasts with usual findings on mate choice. However, body size might not be a reliable quality indicator because males of different cohorts can experience different conditions throughout their life. The caudal filament, grown each breeding period, likely reflects male condition. By assessing such a character, females might evaluate the performance of a potential partner in the current environment regardless of its age. © 2007 Brill Academic Publishers

Characterization of the membrane tubulation mechanism induced by the Toxoplasma GRA2 protein

International audienceWithin the host cell, the parasitophorous vacuole in which Toxoplasma gondii develops, is characterized by a membranous nanotubular network (MNN). The molecular components, the formation and the function of the MNN remain poorly explored.We had previously demonstrated indirectly that the secreted dense granule GRA2 protein, which contains three amphipathic alpha helices, is a key element of the MNN formation (Mercier et al., 2002; Travier et al., 2008). The aim of this work was to demonstrate directly the role of GRA2 in the MNN formation, using an in vitro system to study the GRA2-membrane interactions. Native and recombinant GRA2 proteins were puri ed from Toxoplasma and from Escherichia coli, respectively. Dynamic light scattering and circular dichroism showed that recombinant GRA2, which folds with an alpha-helical pattern, is puri ed as both a potential dimer and complexes of higher molecular weight. When incubated with Small Unilamellar Vesicles (SUVs) formed with complex lipids, both native and recombinant GRA2 were shown to associate with the SUV membranes and to induce the formation of long membranous tubules observed by transmission electron microscopy (TEM). In the literature, it has been reported that most proteins capable of inducing membrane curvature, interact with phosphatidylinositol (4,5) bi-phosphate (PI(4,5)P2). Fat blots and binding assays of GRA2 to SUVs of de ned lipid composition and containing PI(4,5)P2 showed that GRA2 recognizes phosphoinositides and associates preferentially with PI(4,5)P2-containing SUVs. TEM showed that GRA2 deforms membranes only when PI(4,5)P2 is present. Together, these results allowed us to propose a model of membrane deformation induced by GRA2, the principal effector of the MNN formation

Molecular features of Hepatitis E Virus circulation in environmental and human samples

International audienc

Modification de la perception des sons sous antiépileptiques : une revue de la littérature et des bases de pharmacovigilance

National audiencePitch perception modifications are among the little-known adverse effects observed with antiepileptics, mainly affecting patients treated with carbamazepine (CBZ). Here, we describe an original French case of pitch perception modification due to CBZ resulting in perfect pitch loss. We also reviewed the literature as well as French and world health organisation global pharmacovigilance database. The case report concerns a 22-year-old patient with perfect pitch with untreated left temporal partial epilepsy. Following a generalized seizure, the introduction of CBZ prolonged release (200mg twice a day) is decided. As soon as CBZ is introduced, the patient notices a change in pitch perception, about a semitone lower. This adverse effect persisted despite a gradual decrease in doses. The patient reported a total recovery of his perfect pitch when CBZ stopped completely 11 years later. In the French pharmacovigilance database, only one other case of pitch perception modification under CBZ was recorded (no cases were found with oxcarbazepine, lacosamide, sodium valproate, lamotrigine, levetiracetam, phenobarbital, phenytoin, primidone, ethosuximide, vigabatrine, felbamate, gabapentin, tiagabine and topiramate). In the literature, 27 cases of pitch perception modification have been published with CBZ, 1 case with oxcarbazepine and 1 case with lacosamide. Pitch perception modification is a very rare adverse effect of CBZ, oxcarbazepine and lacosamide, identified in the literature mainly in the Japanese population, in experienced musicians. A rapid onset after the introduction of treatment, a complete resolution of symptoms, in most cases upon discontinuation of treatment, is observed, with no sequelae reported. Due to the impact on quality of life, especially in patients whose profession is related to music, knowledge of this adverse event seems important to evoke this diagnosis