Ubiquitous urease affects soybean susceptibility to fungi

The soybean ubiquitous urease (encoded by GmEu4) is responsible for recycling metabolically derived urea. Additional biological roles have been demonstrated for plant ureases, notably in toxicity to other organisms. However, urease enzymatic activity is not related to its toxicity. The role of GmEu4 in soybean susceptibility to fungi was investigated in this study. A differential expression pattern of GmEu4 was observed in susceptible and resistant genotypes of soybeans over the course of a Phakopsora pachyrhizi infection, especially 24 h after infection. Twenty-nine adult, transgenic soybean plants, representing six independently transformed lines, were obtained. Although the initial aim of this study was to overexpress GmEu4, the transgenic plants exhibited GmEu4 co-suppression and decreased ureolytic activity. The growth of Rhizoctonia solani, Phomopsis sp., and Penicillium herguei in media containing a crude protein extract from either transgenic or non-transgenic leaves was evaluated. The fungal growth was higher in the protein extracts from transgenic urease-deprived plants than in extracts from non-transgenic controls. When infected by P. pachyrhizi uredospores, detached leaves of urease-deprived plants developed a significantly higher number of lesions, pustules and erupted pustules than leaves of non-transgenic plants containing normal levels of the enzyme. The results of the present work show that the soybean plants were more susceptible to fungi in the absence of urease. It was not possible to overexpress active GmEu4. For future work, overexpression of urease fungitoxic peptides could be attempted as an alternative approach.     

Telomere length in healthy newborns is not affected by adverse intrauterine environments

Different intrauterine exposures are associated with different metabolic profiles leading to growth and development characteristics in children and also relate to health and disease patterns in adult life. The objective of this work was to evaluate the impact of four different intrauterine environments on the telomere length of newborns. This is a longitudinal observational study using a convenience sample of 222 mothers and their term newborns (>37 weeks of gestational age) from hospitals in Porto Alegre, Rio Grande do Sul (Brazil), from September 2011 to January 2016. Sample was divided into four groups: pregnant women with Gestational Diabetes Mellitus (DM) (n=38), smoking pregnant women (TOBACCO) (n=52), mothers with small-for-gestational age (SGA) children due to idiopathic intrauterine growth restriction (n=33), and a control group (n=99). Maternal and newborn genomic DNA were obtained from epithelial mucosal cells. Telomere length was assessed by qPCR, with the calculation of the telomere and single copy gene (T/S ratio). In this sample, there was no significant difference in telomere length between groups (p>0.05). There was also no association between childbirth weight and telomere length in children (p>0.05). For term newborns different intrauterine environments seems not to influence telomere length at birth.     

Focus Issue on Roots: It’s Complicated: Intraroot System Variability of Respiration and Morphological Traits in Four Deciduous Tree Species

Within branched root systems, a distinct heterogeneity of traits exists. Knowledge about the ecophysiology of different root types is critical to understand root system functioning. Classification schemes have to match functional root types as closely as possible to be used for sampling and modeling. Among ecophysiological root traits, respiration is of particular importance, consuming a great amount of carbon allocated. Root architecture differs between the four deciduous tree seedlings. However, two types of terminal root segments (i.e. first and second orders), white colored and brown colored, can be distinguished in all four species but vary in frequency, their morphology differing widely from each other and higher coarse root orders. Root respiration is related to diameter and tissue density. The use of extended root ordering (i.e. order and color) explains the variance of respiration two times as well as root diameter or root order classes alone. White terminal roots respire significantly more than brown ones; both possess respiration rates that are greater than those of higher orders in regard to dry weight and lower in regard to surface area. The correlation of root tissue density to respiration will allow us to use this continuous parameter (or easier to determine dry matter content) to model the respiration within woody root systems without having to determine nitrogen contents. In addition, this study evidenced that extended root orders are better suited than root diameter classes to picture the differences between root functional types. Together with information on root order class frequencies, these data allow us to calculate realistic, species-specific respiration rates of root branches.In response to environmental parameters, whole-root systems exhibit high plasticity at different hierarchical scales, such as physiology, anatomy, morphology, and/or biomass (Deak and Malamy, 2005; Gruber et al., 2011). However, within branched systems of single-root units, a distinct heterogeneity of root traits is also present, especially in but not limited to woody root systems (Rewald et al., 2011). Thus, a key to the understanding of the functioning of root systems is knowledge of the traits of individual root segments, especially those related to water and nutrient uptake as well as carbon invested. Currently, several systems are used to classify roots within a branching root system. It is important that classes, when used as a basis for root sampling, are not arbitrary but matched as closely as possible to functional categories (Pregitzer et al., 1998); thus, classification schemes that are able to represent different types of root segments best have to be identified.The most commonly used classification system in woody plants is based on root diameters (Böhm, 1979), usually distinguishing rather ephemeral fine roots (diameter = 0–2 mm) from woody coarse roots (diameter ≥ 2 mm). Root diameter is one of the most important input parameters for root and rhizosphere modeling (Himmelbauer et al., 2004), likely because of the convenient determination by image analyses programs or during hand sorting. In contrast, two principal ways to number segments are used: centrifugal (i.e. basal to distal) or centripetal (i.e. distal to basal) ordering (Uylings et al., 1975). Today, the centrifugal ordering scheme is most commonly used (Fitter, 1996), especially by researchers describing root system development and root phenology of crop species (Chen et al., 2011; Clark et al., 2013; Leitner et al., 2014), but it has also been applied on tree roots (Pregitzer et al., 1997; Majdi et al., 2001). In contrast, ordering in centripetal systems (Strahler, 1957) is initiated at most distal segments, and order number is increased when two root segments of equal order meet (Pregitzer, 2002). Although the dynamics of centripetal systems are opposite to those of root system development, they group functionally similar terminal (most distal) tree segments, such as root tips, into the same order. In addition to those approaches, several researchers have successfully used individual classification parameters to distinguish root segments according to color (Goldfarb et al., 1990; Bouma et al., 2000) or characteristic branching patterns (e.g. cluster roots; Neumann and Martinoia, 2002). With respect to color, tree roots are predominantly regarded to be white when first produced, turning brown with age (Wells and Eissenstat, 2003).The respiration of CO₂ from fine roots is an important component of the terrestrial carbon cycle. Root respiration (RR) accounts for 25% to 60% of total soil respiration (Pregitzer et al., 1997; Epron et al., 1999; Dannoura et al., 2006a, 2006b) and consumes up to 75% of carbon allocated to roots (Majdi et al., 2007). Predictions on whole-plant carbon budget estimate that total plant respiration is about one-half of gross primary production (Chapin et al., 2012). In temperate forests, belowground net primary production is about 40% of total net primary production. However, large uncertainties remain in quantifying the allocation of carbon to tree root systems in general and the amount of RR of the whole-tree carbon budget in particular. Therefore, factors that describe the metabolic activity of roots and associated microbes are an important component of determining plant carbon budgets and allocation pattern more precisely. Physiologically, fine RR is critical for root maintenance and growth and one important variable determining the uptake efficiency of roots (George et al., 2003) alongside construction costs (Poorter, 1994). Ion transport across membranes may account for 25% to 50% of RR (Lambers et al., 2008). Previous measurements emphasized that fine RR rates can be highly variable (Pregitzer et al., 1998; Makita et al., 2009). This variability is probably partially because of the arbitrary classification of fine roots based on diameter rather than an anatomical or physiological basis (Bouma et al., 2000; Makita et al., 2009). Although positive correlations between fine RR and nitrogen contents have been established, with young roots having greater nitrogen contents, much of the variation in RR rate within a diameter class must be caused by other factors (Pregitzer et al., 1998). In the last decade, evidence increased that root traits often vary according to the position of individual roots segments among the root branching hierarchy (Pagès and Kervella, 1990; Pregitzer et al., 2002; Wang et al., 2006; Guo et al., 2008a, 2008b; Valenzuela-Estrada et al., 2008; Beyer et al., 2013) and that analysis by root order is one powerful approach to understand complex woody root systems under stress (Rewald et al., 2012). Thus, it is surprising that few attempts (Jia et al., 2013) have been made to test if root order-based classification is covering root system heterogeneity in respiration in a meaningful way and morphological parameters on which it may be based.The aim of this study is to describe the relationship between RR of four deciduous European tree species and continuous root morphological traits and root classes. Our hypotheses are that: (1) root architectural and morphological traits of woody tree species can be best described by extended centripetal root order classification and (2) RR is highly reflected by morphological traits. (3) Additionally, if sampling classes are used, extended root order classification has a significantly greater explanatory value than root diameter classes. Furthermore, we evaluate if upscaling of respiration rates per root order class can be used to compare species-specific RR rates—information that is scarce for European tree species.     

Selective binding and lateral clustering of α5β1 and αvβ3 integrins: Unraveling the spatial requirements for cell spreading and focal adhesion assembly

ABSTRACT

Coordination of the specific functions of α5β1 and αvβ3 integrins is crucial for the precise regulation of cell adhesion, spreading and migration, yet the contribution of differential integrin-specific crosstalk to these processes remains unclear. To determine the specific functions of αvβ3 and α5β1 integrins, we used nanoarrays of gold particles presenting immobilized, integrin-selective peptidomimetic ligands. Integrin binding to the peptidomimetics is highly selective, and cells can spread on both ligands. However, spreading is faster and the projected cell area is greater on α5β1 ligand; both depend on ligand spacing. Quantitative analysis of adhesion plaques shows that focal adhesion size is increased in cells adhering to αvβ3 ligand at 30 and 60 nm spacings. Analysis of αvβ3 and α5β1 integrin clusters indicates that fibrillar adhesions are more prominent in cells adhering to α5β1 ligand, while clusters are mostly localized at the cell margins in cells adhering to αvβ3 ligand. αvβ3 integrin clusters are more pronounced on αvβ3 ligand, though they can also be detected in cells adhering to α5β1 ligand. Furthermore, α5β1 integrin clusters are present in cells adhering to α5β1 ligand, and often colocalize with αvβ3 clusters. Taken together, these findings indicate that the activation of αvβ3 integrin by ligand binding is dispensable for initial adhesion and spreading, but essential to formation of stable focal adhesions.     

Imaging the permeability pore transition in single mitochondria.

In mitochondria the opening of a large proteinaceous pore, the "mitochondrial permeability transition pore" (MTP), is known to occur under conditions of oxidative stress and matrix calcium overload. MTP opening and the resulting cellular energy deprivation have been implicated in processes such as hypoxic cell damage, apoptosis, and neuronal excitotoxicity. Membrane potential (delta psi(m)) in single isolated heart mitochondria was measured by confocal microscopy with a voltage-sensitive fluorescent dye. Measurements in mitochondrial populations revealed a gradual loss of delta psi(m) due to the light-induced generation of free radicals. In contrast, the depolarization in individual mitochondria was fast, sometimes causing marked oscillations of delta psi(m). Rapid depolarizations were accompanied by an increased permeability of the inner mitochondrial membrane to matrix-entrapped calcein (approximately 620 Da), indicating the opening of a large membrane pore. The MTP inhibitor cyclosporin A significantly stabilized delta psi(m) in single mitochondria, thereby slowing the voltage decay in averaged recordings. We conclude that the spontaneous depolarizations were caused by repeated stochastic openings and closings of the transition pore. The data demonstrate a much more dynamic regulation of membrane permeability at the level of a single organelle than predicted from ensemble behavior of mitochondrial populations.     

Genetic analysis of mutations causing borrelidin resistance by overproduction of threonyl-transfer ribonucleic acid synthetase.

Mutations leading to borrelidin resistance in Escherichia coli by overproduction of threonyl-transfer ribonucleic acid synthetase were anaylzed genetically. The regulatory mutations were closely linked to the treonyl-transfer ribonucleic acid synthetase structural gene (thrS), located clockwise to it. The mutation that causes the threefold-increased enzyme level was more distant from thrS than the mutation responsible for the ninefold overproduction. Both mutations were cis dominant in merodiploid strains, indicating that they affected promoter-operator-like control elements. Overproduction was restricted to threonyl-transfer ribonucleic acid synthetase and was not observed for the products of genes neighboring thrS (e.g., infC, pheS, pheT, and argS), providing evidence that thrS is transcribed singly and that gene amplificationis not a likely basis for increased thrS experession.