Plant regeneration from hypocotyl segments of Lupinus luteus cv. L. Aurea

Complete plants of Lupinus luteus L. cv. Aurea that were regenerated from hypocotyl segments, bloomed, produced seeds and were efficiently nodulated by Bradyrhizobium sp. strains. The highest rates of shoot formation were obtained on A medium plus 1.3% agar with 10.0 M 2-isopentenyladenine (2iP) and 0.11 M naphthaleneacetic acid (NAA); the best rooting was achieved on a medium with 0.5 M NAA plus 0.05 M 2iP. Afterward, plantlets were transferred to either perlite or peat-containing pots and irrigated with a N-free nutrient solution until maturity. Direct rooting of hypocotyls could also be obtained on A medium with 1% agar.     

Molecular chaperones and the biogenesis of mitochondria and peroxisomes

Summary— A review of the proteinaceous machinery involved in protein sorting pathways and protein folding and assembly in mitochondria and peroxisomes is presented. After considering the various sorting pathways and targeting signals of mitochondrial and peroxisomal proteins, we make a comparative dissection of the protein factors involved in: i) the stabilization of cytosolic precursor proteins in a translocation competent conformation; ii) the membrane import apparatus of mitochondria and peroxisomes; iii) the processing of mitochondrial precursor proteins, and the eventual processing of certain peroxisomal precursor, in the interior of the organelles; and iv) the requirement of molecular chaperones for appropriate folding and assembly of imported proteins in the matrix of both organelles. Those aspects of mitochondrial biogenesis that have developed rapidly during the last few years, such as the requirement of molecular chaperones, are stressed in order to stimulate further parallel investigations aimed to understand the origin, biochemistry, molecular biology and pathology of peroxisomes. In this regard, a brief review of findings from our group and others is presented in which the role of the F₁-ATPase α-subunit is pointed out as a molecular chaperone of mitochondria and chloroplasts. In addition, data are presented that could question our previous indication that the immunoreactive protein found in the rat liver peroxisomes is due to the presence of the F₁-ATPase α-subunit.     

Distribution of microtubules during the growth of tobacco pollen tubes

Summary— The distribution of microtubules was investigated in Nicotiana tabacum pollen tubes at different stages of tube growth by immunofluorescence microscopy. Using specific antibodies, the presence of microtubules consisting of different tubulin isoforms was tested. α-, β- and tyrosinated α-tubulin were present within the tube, whereas the acetylated form was lacking. The presence of tubulin subunits in pollen tube extracts was also investigated by immunoblotting analyses. The use of a confocal laser scanning microscope integrated with computer-assisted imaging, allowed a detailed visualization of the microtubule distribution and organization. Cytoplasmic microtubules organized as short bundles with various orientations were detected at the apex of long tubes.     

Thermostable β-Glycosidase from Sulfolobus Solfataricus

The Sulfolobus solfataricus β-glycosidase (Sβgly) is a thermostable and thermophilic glycosyl-hydrolase with broad substrate specificity. The enzyme hydrolizes β-D-gluco-, fuco-, and galactosides, and a large number of /Winked glycoside dimers and oligomers, linked β1-3, β1-4, and β1-6, It is able to hydrolize oligosaccharides with up to 5 glucose residues. Furthermore, it is also able to promote transglycosylation reactions. The corresponding gene has been cloned and overexpressed both in yeast and Escherichia coli. Based on sequence and functional data, the Sβgly has been assigned to the so-called BGA family of glycosyl-hydrolases, including β-glycosidases, β-galactosidases and phosho-β-galactosidases from mesophilic and thermophilic organisms of the three domains. The Sβgly has been crystallized and the resolution of its structure is in progress. Because of its special properties, the enzymes has considerable biotechnological potential.     

Chemical structure and conformational features of cell-wall polysaccharides isolated from Aphanoascus mephitalus and related species

The structures of cell-wall mannans isolated from Aphamoascus mephitalus, A. Fulvescens, A. verrucosus, and A. reticulisporus have been investigated by chemical analyses and 1D and 2D ¹H and ¹³C NMR techniques. It was found that all of them consists of a relatively simple comb-like structure of the disaccharide repeating block {→ 6)-[-Man p-(1 → 2)]--Man p-(1 →}. The conformations around the -(1 → 2) and -(1 → 6) linkages in thes kinds of polymers were also studied by using molecular mechanics and dynamics calculations, together with NOE data. The results are similar to those found within the oligosaccharide chains of glycoproteins, with a well-defined conformation for the -(1 → 2) linkage and a certain restriction around the -(1 → 6) bonding imposed by the 2-substitution.     

The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence

The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes: precipitation, evaporation, runoff, and atmospheric moisture convergence (net import of water vapor to balance runoff). Each of these processes is essential for sustaining human and ecosystem well-being. Predicting how the water cycle responds to changes in vegetation cover remains a challenge. Recently, changes in plant transpiration across the Amazon basin were shown to be associated disproportionately with changes in rainfall, suggesting that even small declines in transpiration (e.g., from deforestation) would lead to much larger declines in rainfall. Here, constraining these findings by the law of mass conservation, we show that in a sufficiently wet atmosphere, forest transpiration can control atmospheric moisture convergence such that increased transpiration enhances atmospheric moisture import and results in water yield. Conversely, in a sufficiently dry atmosphere increased transpiration reduces atmospheric moisture convergence and water yield. This previously unrecognized dichotomy can explain the otherwise mixed observations of how water yield responds to re-greening, as we illustrate with examples from China's Loess Plateau. Our analysis indicates that any additional precipitation recycling due to additional vegetation increases precipitation but decreases local water yield and steady-state runoff. Therefore, in the drier regions/periods and early stages of ecological restoration, the role of vegetation can be confined to precipitation recycling, while once a wetter stage is achieved, additional vegetation enhances atmospheric moisture convergence and water yield. Recent analyses indicate that the latter regime dominates the global response of the terrestrial water cycle to re-greening. Evaluating the transition between regimes, and recognizing the potential of vegetation for enhancing moisture convergence, are crucial for characterizing the consequences of deforestation as well as for motivating and guiding ecological restoration.     

Influence of plant domestication on plant-pollinator interactions: Floral attributes and floral visitor communities in wild and cultivated squash plants

Premise

Domestication of plant species results in phenotypic modifications and changes in biotic interactions. Most studies have compared antagonistic plant-herbivore interactions of domesticated plants and their wild relatives, but little attention has been given to how domestication influences plant-pollinator interactions. Floral attributes and interactions of floral visitors were compared between sister taxa of the genus Cucurbita (Cucurbitaceae), the domesticated C. moschata, C. argyrosperma ssp. argyrosperma and its wild progenitor C. argyrosperma ssp. sororia in the place of origin.

Methods

We conducted univariate and multivariate analyses to compare floral morphological traits and analyzed floral reward (nectar and pollen) quantity and quality between flowers of wild and domesticated Cucurbita taxa. Staminate and pistillate flowers of all three taxa were video recorded, and visitation and behavior of floral visitors were registered and analyzed.

Results

Most floral morphological characteristics of flowers of domesticated taxa were larger in both staminate and pistillate flowers. Staminate and pistillate flowers presented distinct correlations between floral traits and integration indices between domesticated and wild species. Additionally, pollen quantity and protein to lipid ratio were greater in domesticated species. Cucurbit pollen specialists, Eucera spp., had the highest probability of visit for all Cucurbita taxa.

Conclusions

We provide evidence that floral traits of domesticated and wild Cucurbita species experienced different selection pressures. Domesticated Cucurbita species may have more resources invested towards floral traits, thereby increasing attractiveness to pollinators and potentially plant reproductive success. Wild ancestor plant populations should be conserved in their centers of origin to preserve plant-pollinator interactions.     

A novel tomato spotted wilt virus isolate encoding a noncanonical NSm C118F substitution associated with Sw-5 tomato gene resistance breaking

The nonstructural protein NSm of tomato spotted wilt virus (TSWV) has been identified as the avirulence determinant of the tomato single dominant Sw-5 resistance gene. Although Sw-5 effectiveness has been shown for most TSWV isolates, the emergence of resistance-breaking (RB) isolates has been observed. It is strongly associated with two point mutations (C118Y or T120N) in the NSm viral protein. TSWV-like symptoms were observed in tomato crop cultivars (+Sw-5) in the Baja California peninsula, Mexico, and molecular methods confirmed the presence of TSWV. Sequence analysis of the NSm 118–120 motif and three-dimensional protein modelling exhibited a noncanonical C118F substitution in seven isolates, suggesting that this substitution could emulate the C118Y-related RB phenotype. Furthermore, phylogenetic and molecular analysis of the full-length genome (TSWV-MX) revealed its reassortment-related evolution and confirmed that putative RB-related features are restricted to the NSm protein. Biological and mutational NSm 118 residue assays in tomato (+Sw-5) confirmed the RB nature of TSWV-MX isolate, and the F118 residue plays a critical role in the RB phenotype. The discovery of a novel TSWV-RB Mexican isolate with the presence of C118F substitution highlights a not previously described viral adaptation in the genus Orthotospovirus, and hence, the necessity of further crop monitoring to alert the establishment of novel RB isolates in cultivated tomatoes.     

Chemical composition and larvicidal activity of essential oils of three Artemisia species

Aedes aegypti L. (Diptera: Culicidae) is a vector for serious diseases in tropical regions. This pest is mainly controlled by commercial larvicides but the application of such products has led to environmental problems. Essential oils (EO) have been consistently reported as molecules with insecticidal activity and can be used to produce more environmentally friendly larvicides in the control of A. aegypti. In this study, the larvicidal effect of essential oils (EO) from the leaves of three Artemisia species was evaluated against A. aegypti. The oils were obtained from steam distillation and their chemical composition was determined by gas chromatography–mass spectrometry. The EO of Artemisia camphorata was the most active in the screening bioassay and presented LC₅₀ and LC₉₅ of 64.95 and 74.18 μg ml⁻¹, respectively. In addition, we found that germacrene D-4-ol was the constituent responsible for the toxicity of this EO. Artemisia camphorata EO and its major constituent, germacrene D-4-ol, are promising for the development of natural larvicides against A. aegypti.