Process of reductive evolution during 10 years in plasmids of a non-insect-transmissible phytoplasma

A non-insect-transmissible phytoplasma strain (OY-NIM) was obtained from insect-transmissible strain OY-M by plant grafting using no insect vectors. In this study, we analyzed for the gene structure of plasmids during its maintenance in plant tissue culture for 10 years. OY-M strain has one plasmid encoding orf3 gene which is thought to be involved in insect transmissibility. The gradual loss of OY-NIM plasmid sequence was observed in subsequent steps: first, the promoter region of orf3 was lost, followed by the loss of then a large region including orf3, and finally the entire plasmid was disappeared. In contrast, no mutation was found in a pseudogene on OY-NIM chromosome in the same period, indicating that OY-NIM plasmid evolved more rapidly than the chromosome-encoded gene tested. Results revealed an actual evolutionary process of OY plasmid, and provide a model for the stepwise process in reductive evolution of plasmids by environmental adaptation. Furthermore, this study indicates the great plasticity of plasmids throughout the evolution of phytoplasma.     

Enhanced Stomatal Conductance by a Spontaneous Arabidopsis Tetraploid,Me-0, Results from Increased Stomatal Size and Greater Stomatal Aperture

The rate of gas exchange in plants is regulated mainly by stomatal size and density. Generally, higher densities of smaller stomata are advantageous for gas exchange; however, it is unclear what the effect of an extraordinary change in stomatal size might have on a plant’s gas-exchange capacity. We investigated the stomatal responses to CO₂ concentration changes among 374 Arabidopsis (Arabidopsis thaliana) ecotypes and discovered that Mechtshausen (Me-0), a natural tetraploid ecotype, has significantly larger stomata and can achieve a high stomatal conductance. We surmised that the cause of the increased stomatal conductance is tetraploidization; however, the stomatal conductance of another tetraploid accession, tetraploid Columbia (Col), was not as high as that in Me-0. One difference between these two accessions was the size of their stomatal apertures. Analyses of abscisic acid sensitivity, ion balance, and gene expression profiles suggested that physiological or genetic factors restrict the stomatal opening in tetraploid Col but not in Me-0. Our results show that Me-0 overcomes the handicap of stomatal opening that is typical for tetraploids and achieves higher stomatal conductance compared with the closely related tetraploid Col on account of larger stomatal apertures. This study provides evidence for whether larger stomatal size in tetraploids of higher plants can improve stomatal conductance.Gas exchange is a vital activity for higher plants that take up atmospheric CO₂ and release oxygen and water vapor through epidermal stomatal pores. Gas exchange affects CO₂ uptake, photosynthesis, and biomass production (Horie et al., 2006; Evans et al., 2009; Tanaka et al., 2014). Stomatal conductance (gs) is used as an indicator of gas-exchange capacity (Franks and Farquhar, 2007). Maximum stomatal conductance (gsmax) is controlled mainly by stomatal size and density, two parameters that change with environmental conditions and are negatively correlated with each other (Franks et al., 2009).Given a constant total stomatal pore area, large stomata are generally disadvantageous for gas exchange compared with smaller stomata, because the greater pore depth in larger stomata increases the distance that gas molecules diffuse through. This increased distance is inversely proportional to g_smax (Franks and Beerling, 2009). The fossil record indicates that ancient plants had small numbers of large stomata when atmospheric CO₂ levels were high, and falling atmospheric [CO₂] induced a decrease in stomatal size and an increase in stomatal density to increase g_s for maximum carbon gain (Franks and Beerling, 2009). The positive relationship between a high g_s and numerous small stomata also holds true among plants living today under various environmental conditions (Woodward et al., 2002; Galmés et al., 2007; Franks et al., 2009). Additionally, the large stomata of several plant species (e.g. Vicia faba and Arabidopsis [Arabidopsis thaliana]) are often not effective for achieving rapid changes in g_s, due to slower solute transport to drive movement caused by their lower membrane surface area-to-volume ratios (Lawson and Blatt, 2014).Stomatal size is strongly and positively correlated with genome size (Beaulieu et al., 2008; Franks et al., 2012; Lomax et al., 2014). Notably, polyploidization causes dramatic increases in nucleus size and stomatal size (Masterson, 1994; Kondorosi et al., 2000). In addition to the negative effects of large stomata on gas exchange (Franks et al., 2009), polyploids may have another disadvantage; del Pozo and Ramirez-Parra (2014) showed that artificially induced tetraploids of Arabidopsis have a reduced stomatal density (stomatal number per unit of leaf area) and a lower stomatal index (stomatal number per epidermal cell number). Moreover, tetraploids of Rangpur lime (Citrus limonia) and Arabidopsis have lower transpiration rates and changes in the expression of genes involved in abscisic acid (ABA), a phytohormone that induces stomatal closure (Allario et al., 2011; del Pozo and Ramirez-Parra, 2014). On the other hand, an increase in the ploidy level of Festuca arundinacea results in an increase in the CO₂-exchange rate (Byrne et al., 1981); hence, polyploids may not necessarily have a reduced gas-exchange capacity.Natural accessions provide a wide range of information about mechanisms for adaptation, regulation, and responses to various environmental conditions (Bouchabke et al., 2008; Brosché et al., 2010). Arabidopsis, which is distributed widely throughout the Northern Hemisphere, has great natural variation in stomatal anatomy (Woodward et al., 2002; Delgado et al., 2011). Recently, we investigated leaf temperature changes in response to [CO₂] in a large number of Arabidopsis ecotypes (374 ecotypes; Takahashi et al., 2015) and identified the Mechtshausen (Me-0) ecotype among ecotypes with low CO₂ responsiveness; Me-0 had a comparatively low leaf temperature, implying a high transpiration rate. In this study, we revealed that Me-0 had a higher g_s than the standard ecotype Columbia (Col), despite having tetraploid-dependent larger stomata. Notably, the g_s of Me-0 was also higher than that of tetraploid Col, which has stomata as large as those of Me-0. This finding resulted from Me-0 having a higher g_s-to-g_smax ratio due to more opened stomata than tetraploid Col. In addition, there were differences in ABA responsiveness, ion homeostasis, and gene expression profiles in guard cells between Me-0 and tetraploid Col, which may influence their stomatal opening. Despite the common trend of smaller stomata with higher gas-exchange capacity, the results with Me-0 confirm the theoretical possibility that larger stomata can also achieve higher stomatal conductance if pore area increases sufficiently.     

Impaired Air Conditioning within the Nasal Cavity in Flat-Faced Homo

We are flat-faced hominins with an external nose that protrudes from the face. This feature was derived in the genus Homo, along with facial flattening and reorientation to form a high nasal cavity. The nasal passage conditions the inhaled air in terms of temperature and humidity to match the conditions required in the lung, and its anatomical variation is believed to be evolutionarily sensitive to the ambient atmospheric conditions of a given habitat. In this study, we used computational fluid dynamics (CFD) with three-dimensional topology models of the nasal passage under the same simulation conditions, to investigate air-conditioning performance in humans, chimpanzees, and macaques. The CFD simulation showed a horizontal straight flow of inhaled air in chimpanzees and macaques, contrasting with the upward and curved flow in humans. The inhaled air is conditioned poorly in humans compared with nonhuman primates. Virtual modifications to the human external nose topology, in which the nasal vestibule and valve are modified to resemble those of chimpanzees, change the airflow to be horizontal, but have little influence on the air-conditioning performance in humans. These findings suggest that morphological variation of the nasal passage topology was only weakly sensitive to the ambient atmosphere conditions; rather, the high nasal cavity in humans was formed simply by evolutionary facial reorganization in the divergence of Homo from the other hominin lineages, impairing the air-conditioning performance. Even though the inhaled air is not adjusted well within the nasal cavity in humans, it can be fully conditioned subsequently in the pharyngeal cavity, which is lengthened in the flat-faced Homo. Thus, the air-conditioning faculty in the nasal passages was probably impaired in early Homo members, although they have survived successfully under the fluctuating climate of the Plio-Pleistocene, and then they moved “Out of Africa” to explore the more severe climates of Eurasia.     

Redescription of Scymnodon ichiharai Yano and Tanaka 1984 (Squaliformes: Somniosidae) from the western North Pacific,with comments on the definition of somniosid genera

Ichthyological Research - The somniosid species Scymnodon ichiharai Yano and Tanaka 1984 is redescribed based on the type specimens and additional material from Taiwan and Japan. The range of this...     

Gads/Grb2-mediated association with LAT is critical for the inhibitory function of Gab2 in T cells

A docking protein, Gab2, is recruited to the vicinity of the TCR complex and inhibits downstream signaling by interaction with negative regulators. However, the molecular mechanisms of this recruitment remain unclear. We have found that Gab2 associates with LAT upon TCR stimulation and that LAT is essential for Gab2 phosphorylation. By analysis of several Gab2 mutants, the c-Met binding domain (MBD) of Gab2 was found to be both necessary and sufficient for stimulation-induced LAT binding. Within the MBD domain, a novel Grb2 SH3 binding motif, PXXXR, is critical for constitutive association with Gads/Grb2. Through this association, Gab2 is recruited to the lipid raft after TCR ligation and exerts inhibitory function. The in vivo significance of this association is illustrated by the fact that T-cell responses are impaired in transgenic mice expressing wild-type Gab2 but not in mice expressing mutant Gab2 lacking the motif. Furthermore, T cells from Gab2-deficient mice showed enhanced proliferative responses upon TCR stimulation. These results indicate that Gads/Grb2-mediated LAT association is critical for the inhibitory function of Gab2, implying that Gab2 induced in stimulated T cells may exert an efficient negative feedback loop by recruiting inhibitory molecules to the lipid raft and competing with SLP-76 through Gads binding.     

Gene expression and intracellular localization of somatolactin in the pituitary of rainbow trout

The gene expression and intracellular localization of somatolactin (SL), a putative pituitary hormone structurally related to both growth hormone and prolactin, were investigated in the pituitary of rainbow trout, Oncorhynchus mykiss. Using an in situ hybridization technique, we demonstrated the gene expression of the SL molecule in cells bordering the neurohypophysial tissue in the pars intermedia. These cells were identified immunocytochemically as SL-cells on the adjacent section. Electron-microscopic immunocytochemistry by means of the protein A-gold technique, also revealed that the SL-immunoreactivity was located mostly on the secretory granules in SL-cells. Our findings clearly indicate that SL is biosynthesized and stored in the granules in these cells.     

Sensitivities to juvenile hormone and ecdysteroid in the diapause larvae of Omphisa fuscidentalis based on the hemolymph trehalose dynamics index

The final instar larva of the bamboo borer, Omphisa fuscidentalis, is in diapause for 9 months from September to the following June. Trehalose and ecdysteroid concentrations in hemolymph were measured through the larval diapause period and in the pupal stage. The ecdysteroid concentration remained low until November, followed by a gradual increase to about 30 ng/ml in May. The trehalose concentration remained at levels ranging between 40-50 mM until May, and decreased to an almost undetectable level after pupation. Since a juvenile hormone analogue (JHA), methoprene, is capable of terminating diapause by stimulating larval prothoracic glands, we examined its effects on ecdysteroid and trehalose concentrations in larvae in December and February. The hemolymph ecdysteroid increased more quickly in February than in December, indicating that the sensitivity of the prothoracic glands to JHA increased towards the end of diapause termination. Similarly, hemolymph trehalose in February decreased within a few days after JHA application, while in December the decrease occurred in the third week. Exogenous 20-hydroxyecdysone (20E) caused a decrease in trehalose concentration in a dose-dependent manner. The effective dose of 20E, however, did not change from January until April, implying that the sensitivity of tissue(s) to 20E may not change until the end of diapause. Taken together, our results suggest that the sensitivities of tissues to JH and 20E do not increase simultaneously with the progress of diapause development and that termination of larval diapause is not associated simply with the restoration of hormone deficiencies.     

Gingival Fibroblasts as a Promising Source of Induced Pluripotent Stem Cells

Background

Induced pluripotent stem (iPS) cells efficiently generated from accessible tissues have the potential for clinical applications. Oral gingiva, which is often resected during general dental treatments and treated as biomedical waste, is an easily obtainable tissue, and cells can be isolated from patients with minimal discomfort.

Methodology/Principal Findings

We herein demonstrate iPS cell generation from adult wild-type mouse gingival fibroblasts (GFs) via introduction of four factors (Oct3/4, Sox2, Klf4 and c-Myc; GF-iPS-4F cells) or three factors (the same as GF-iPS-4F cells, but without the c-Myc oncogene; GF-iPS-3F cells) without drug selection. iPS cells were also generated from primary human gingival fibroblasts via four-factor transduction. These cells exhibited the morphology and growth properties of embryonic stem (ES) cells and expressed ES cell marker genes, with a decreased CpG methylation ratio in promoter regions of Nanog and Oct3/4. Additionally, teratoma formation assays showed ES cell-like derivation of cells and tissues representative of all three germ layers. In comparison to mouse GF-iPS-4F cells, GF-iPS-3F cells showed consistently more ES cell-like characteristics in terms of DNA methylation status and gene expression, although the reprogramming process was substantially delayed and the overall efficiency was also reduced. When transplanted into blastocysts, GF-iPS-3F cells gave rise to chimeras and contributed to the development of the germline. Notably, the four-factor reprogramming efficiency of mouse GFs was more than 7-fold higher than that of fibroblasts from tail-tips, possibly because of their high proliferative capacity.

Conclusions/Significance

These results suggest that GFs from the easily obtainable gingival tissues can be readily reprogrammed into iPS cells, thus making them a promising cell source for investigating the basis of cellular reprogramming and pluripotency for future clinical applications. In addition, high-quality iPS cells were generated from mouse GFs without Myc transduction or a specific system for reprogrammed cell selection.     

Interactions between Serum Vitamin D Levels and Vitamin D Receptor Gene FokI Polymorphisms for Renal Function in Patients with Type 2 Diabetes

Background

We aimed to examine associations among serum 25-hydroxyvitamin D (25OHD) levels, 1,25-dihyroxyvitamin D (1,25OHD) levels, vitamin D receptor (VDR) polymorphisms, and renal function based on estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes.

Methods

In a cross-sectional study of 410 patients, chronic kidney disease (CKD) stage assessed by eGFR was compared with 25OHD, 1,25OHD, and VDR FokI (rs10735810) polymorphisms by an ordered logistic regression model adjusted for the following confounders: disease duration, calendar month, use of angiotensin converting enzyme inhibitors/angiotensin receptor blockers or statins, and serum calcium, phosphate, and intact parathyroid hormone levels.

Results

1,25OHD levels, rather than 25OHD levels, showed seasonal oscillations; peak levels were seen from May to October and the lowest levels were seen from December to February. These findings were evident in patients with CKD stage 3∼5 but not stage 1∼2. eGFR was in direct proportion to both 25OHD and 1,25OHD levels (P<0.0001), but it had stronger linearity with 1,25OHD (r = 0.73) than 25OHD (r = 0.22) levels. Using multivariate analysis, 1,25OHD levels (P<0.001), but not 25OHD levels, were negatively associated with CKD stage. Although FokI polymorphisms by themselves showed no significant associations with CKD stage, a significant interaction between 1,25OHD and FokITT was observed (P = 0.008). The positive association between 1,25OHD and eGFR was steeper in FokICT and CC polymorphisms (r = 0.74) than FokITT polymorphisms (r = 0.65).

Conclusions

These results suggest that higher 1,25OHD levels may be associated with better CKD stages in patients with type 2 diabetes and that this association was modified by FokI polymorphisms.