Extremely high intracellular concentration of glucose-6-phosphate and NAD(H) in Deinococcus radiodurans

Extremophiles - Deinococcus radiodurans is highly resistant to ionizing radiation and UV radiation, and oxidative stress caused by such radiations. NADP(H) seems to be important for this resistance...     

Intrauterine Ischemic Reperfusion Switches the Fetal Transcriptional Pattern from HIF-1α- to P53-Dependent Regulation in the Murine Brain

Ischemic reperfusion (IR) during the perinatal period is a known causative factor of fetal brain damage. So far, both morphologic and histologic evidence has shown that fetal brain damage can be observed only several hours to days after an IR insult has occurred. Therefore, to prevent fetal brain damage under these circumstances, a more detailed understanding of the underlying molecular mechanisms involved during an acute response to IR is necessary. In the present work, pregnant mice were exposed to IR on day 18 of gestation by clipping one side of the maternal uterine horn. Simultaneous fetal electrocardiography was performed during the procedure to verify that conditions resulting in fetal brain damage were met. Fetal brain sampling within 30 minutes after IR insult revealed molecular evidence that a fetal response was indeed triggered in the form of inhibition of the Akt-mTOR-S6 synthesis pathway. Interestingly, significant changes in mRNA levels for both HIF-1α and p53 were apparent and gene regulation patterns were observed to switch from a HIF-1α-dependent to a p53-dependent process. Moreover, pre-treatment with pifithrin-α, a p53 inhibitor, inhibited protein synthesis almost completely, revealing the possibility of preventing fetal brain damage by prophylactic pifithrin-α treatment.     

Roles of ADAM13-regulated Wnt activity in early Xenopus eye development

Pericellular proteolysis by ADAM family metalloproteinases has been widely implicated in cell signaling and development. We recently found that Xenopus ADAM13, an ADAM metalloproteinase, is required for activation of canonical Wnt signaling during cranial neural crest (CNC) induction by regulating a novel crosstalk between Wnt and ephrin B (EfnB) signaling pathways (Wei et al., 2010b). In the present study we show that the metalloproteinase activity of ADAM13 also plays important roles in eye development in Xenopus tropicalis. Knockdown of ADAM13 results in reduced expression of eye field markers pax6 and rx1, as well as that of the pan-neural marker sox2. Activation of canonical Wnt signaling or inhibition of forward EfnB signaling rescues the eye defects caused by loss of ADAM13, suggesting that ADAM13 functions through regulation of the EfnB-Wnt pathway interaction. Downstream of Wnt, the head inducer Cerberus was identified as an effector that mediates ADAM13 function in early eye field formation. Furthermore, ectopic expression of the Wnt target gene snail2 restores cerberus expression and rescues the eye defects caused by ADAM13 knockdown. Together these data suggest an important role of ADAM13-regulated Wnt activity in eye development in Xenopus.     

Clonal growth and its effects on male and female reproductive success in <Emphasis Type="Italic">Prunus ssiori</Emphasis> (Rosaceae)

Clonal growth can increase not only floral display but also geitonogamy and may affect sexual reproduction both positively and negatively. A clonal woody species, Prunus ssiori, was partially self-incompatible according to a pollination experiment. Its main pollinators, bumble bees, were often observed to consecutively visit inflorescences within a tree. Clone identification revealed that its genets formed mutually exclusive patches. These features suggest frequent geitonogamous pollination. In a 6.24-ha plot, 212 trees belonged to 59 genets, and 42 genets consisted of a single tree, whereas the rest contained two or more clonal trees. The largest genet had 65 trees and occupied 0.4 of a hectare. Fruit set was measured in 127 inflorescences sampled from nine maternal trees at the center of the plot. Paternal genets of 107 of their 300 seeds were assigned in the plot using microsatellites. There were no selfed seeds. Male reproductive success (the probability that individual trees of each genet sired a seed) increased as tree size increased, as the distance between the trees and maternal trees decreased, when the genet did not contain the maternal trees, and when the genet consisted of a single tree. Female reproductive success (fruit set in individual inflorescences of each maternal tree) increased as the within-tree geitonogamy index, which reflected the frequency of pollination within the maternal tree, decreased. These results suggest that clonal growth reduces male reproductive success, at least, in P. ssiori, because of pollen discounting.     

A Secreted Protein with Plant-Specific Cysteine-Rich Motif Functions as a Mannose-Binding Lectin That Exhibits Antifungal Activity

Plants have a variety of mechanisms for defending against plant pathogens and tolerating environmental stresses such as drought and high salinity. Ginkbilobin2 (Gnk2) is a seed storage protein in gymnosperm that possesses antifungal activity and a plant-specific cysteine-rich motif (domain of unknown function26 [DUF26]). The Gnk2-homologous sequence is also observed in an extracellular region of cysteine-rich repeat receptor-like kinases that function in response to biotic and abiotic stresses. Here, we report the lectin-like molecular function of Gnk2 and the structural basis of its monosaccharide recognition. Nuclear magnetic resonance experiments showed that mannan was the only yeast (Saccharomyces cerevisiae) cell wall polysaccharide that interacted with Gnk2. Gnk2 also interacted with mannose, a building block of mannan, with a specificity that was similar to those of mannose-binding legume lectins, by strictly recognizing the configuration of the hydroxy group at the C4 position of the monosaccharide. The crystal structure of Gnk2 in complex with mannose revealed that three residues (asparagine-11, arginine-93, and glutamate-104) recognized mannose by hydrogen bonds, which defined the carbohydrate-binding specificity. These interactions were directly related to the ability of Gnk2 to inhibit the growth of fungi, including the plant pathogenic Fusarium spp., which were disrupted by mutation of arginine-93 or the presence of yeast mannan in the assay system. In addition, Gnk2 did not inhibit the growth of a yeast mutant strain lacking the α1,2-linked mannose moiety. These results provide insights into the molecular basis of the DUF26 protein family.Plants have evolved to survive in environments that expose them to various stress factors. Being sessile, plants have developed specific mechanisms for defending against plant pathogens and responding to environmental stress conditions. These mechanisms serve to minimize damage while conserving valuable resources for growth and reproduction. For the biotic stresses caused by pathogen infections, plants have a variety of defense mechanisms such as hypersensitive responses, reinforcement of cell walls, and synthesis of phytoalexins and antifungal proteins (Hammond-Kosack and Jones, 1996; de Wit, 2007; Hamann, 2012). Abiotic stresses such as drought and high salinity also have adverse effects on plant physiology and metabolism. Plant cells respond and adapt to these adverse conditions by sensing them through receptor proteins on the plasma membrane and by mechanisms such as abscisic acid (ABA) signaling (Umezawa et al., 2010; Miyakawa et al., 2013; Osakabe et al., 2013). In fact, there is intricate cross talk among these stress responses on multiple molecular levels (Atkinson and Urwin, 2012).The genes coding the plant-specific Cys-rich motif (domain of unknown function26 [DUF26]) make up a large gene family, and the motif was initially found in the extracellular region of cysteine-rich receptor-like kinases (CRKs) and Cys-rich secretory proteins from Arabidopsis (Arabidopsis thaliana; Chen, 2001). Several CRKs are involved in resistance to bacterial and fungal pathogens, hypersensitive response-related cell death, oxidative stress responses, and salicylic acid-dependent defense pathways (Czernic et al., 1999; Du and Chen., 2000; Ohtake et al., 2000; Chen et al., 2003; Acharya et al., 2007; Wrzaczek et al., 2010; Rayapuram et al., 2012). A recent study also showed that some CRKs regulate ABA signaling and osmotic stress responses (Tanaka et al., 2012). In addition, another DUF26-containing secretory protein, Oryza sativa root meander curling, was implicated in the salt stress response in rice (Oryza sativa; Zhang et al., 2009). These findings support the idea that the DUF26 proteins have evolved to cope with various biotic and abiotic stresses in plants. However, the molecular basis of DUF26 proteins remains unclear in spite of their physiological significance.In a previous study, we identified a secreted DUF26 protein with antifungal activity, ginkbilobin2 (Gnk2), from gymnosperm Ginkgo biloba seeds (Sawano et al., 2007). Gnk2 consists of 108 amino acids as a mature protein and inhibits the growth of phytopathogenic fungi such as Fusarium oxysporum. This antifungal protein shows no sequence similarity to other antifungal proteins (Sawano et al., 2007) and thus exhibits a structure quite distinct from theirs (Miyakawa et al., 2009). Gnk2 orthologs are also found as embryo abundant proteins in two other gymnosperm species: Picea abies and Picea glauca (Sawano et al., 2007). Their sequences are not homologous to any classes of late-embryogenesis abundant proteins (Dong and Dunstan, 1999; Hong-Bo et al., 2005). In addition, the gene expressions of embryo abundant proteins are not affected by ABA, a stimulator for somatic embryo maturation, unlike the gene expressions of late-embryogenesis abundant proteins (Dong and Dunstan, 1999). These findings raise the possibility that Gnk2-like proteins function in biotic stress responses and in seed development via a specific molecular mechanism.Many pathogenesis-related proteins with antifungal activity initially target the cell wall components of fungi, including the cell wall structure and plasma membrane (Selitrennikoff, 2001). Using a NMR technique, we show that mannan is the only cell wall component with which Gnk2 interacts. Our series of structural and biochemical experiments revealed that Gnk2 functions as a lectin and that its carbohydrate-binding properties are tightly related to its antifungal activity; these are the first insights into the molecular basis of the functioning of DUF26 protein family members.