From July to March, the testis of the spring-spawning freshwater goby Padogobius martensi is characterized by spermatogonial proliferation. A close correlation exists among type of proliferating spermatogonia, gonado-somatic (I G ) profiles and morphological and functional variations of the Leydig cells. The I G reach their minimal levels by the end of summer and increase progressively but modestly during autumn and winter. Declining I G levels are associated with proliferation of primary spermatogonia only, whereas increasing I G levels are associated with predominant proliferation of secondary spermatogonia. Minimal I G levels are reached when the germinal epithelium is formed by a continuum of primary spermatogonia and associated Sertoli cells. The proliferation of secondary spermatogonia begins only at this time. Spermatogenesis in autumn occurs when spermatogonial cysts contain at the most 16 cells and it rarely results in the maturation of several cysts so that the amount of sperm cells produced is either negligible or scarce. A number of degenerating cells are usually present within the spermatogonial and meiotic cysts. Leydig cells are the unique cells that display features of steroidogenic cells: mitochondria with tubular cristae, extensive smooth endoplasmic reticulum (SER), 3b-hydroxysteroid dehydrogenase (3b-HSD) and glucose-6-phosphate dehydrogenase (G6PD) activity and sudanophilia. Light and dark Leydig cell varieties are always present. During regression, Leydig cells undergo a marked decrease in SER amount, mitochondrial sizes and number of mitochondrial cristae. In parallel, the 3b-HSD and G6PD activities and sudanophilia decrease progressively until they become undetectable by the end of regression. In autumn, mitochondria increase in size, reaching sizes similar to those observed at the end of the spawning season in the light cells, but not in the dark cells. The SER, on the contrary, undergoes a modest and irregular increase only in a part of the Leydig cells, mostly of the light type. In parallel, the 3b-HSD and G6PD activities increase until they become moderately intense by the end of autumn. At the end of winter, the SER is extensive and regularly dilated in both Leydig cell types, whereas mitochondria still have sizes similar to those observed in December. The 3b-HSD and G6PD activities are strong and sudanophilia is again detectable. Sertoli cells undergo changes in shape and position in relation to the proliferation of primary spermatogonia and the development of cysts. A junction modulation occurs in association with these changes. Sertoli cells also undergo changes indicative of a decrease in activity immediately after spawning (loss of mitochondrial cristae and clarification of the mitochondrial matrix) and of an increase in activity by the end of the regressing phase (darkening of the mitochondrial matrix and increase in mitochondrial cristae, rough endoplasmic reticulum (RER) and free ribosomes). In addition, they are involved in the phagocytosis of degenerating germ cells at all s...

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Asexual propagation in Ceratonia siliqua L.

This study assesses the effects of specific bacterial endophytes on the phytoextraction capacity of the Ni-hyperaccumulator Noccaea caerulescens, spontaneously growing in a serpentine soil environment. Five metal-tolerant endophytes had already been selected for their high Ni tolerance (6 mM) and plant growth promoting ability. Here we demonstrate that individual bacterial inoculation is ineffective in enhancing Ni translocation and growth of N. caerulescens in serpentine soil, except for specific strains Ncr-1 and Ncr-8, belonging to the Arthrobacter and Microbacterium genera, which showed the highest indole acetic acid production and 1-aminocyclopropane-1-carboxylic acid-deaminase activity. Ncr-1 and Ncr-8 co-inoculation was even more efficient in promoting plant growth, soil Ni removal, and translocation of Ni, together with that of Fe, Co, and Cu. Bacteria of both strains densely colonized the root surfaces and intercellular spaces of leaf epidermal tissue. These two bacterial strains also turned out to stimulate root length, shoot biomass, and Ni uptake in Arabidopsis thaliana grown in MS agar medium supplemented with Ni. It is concluded that adaptation of N. caerulescens in highly Ni-contaminated serpentine soil can be enhanced by an integrated community of bacterial endophytes rather than by single strains; of the former, Arthrobacter and Microbacterium may be useful candidates for future phytoremediation trials in multiple metal-contaminated sites, with possible extension to non-hyperaccumulator plants.

The foliar pathogen Pseudomonas syringae pv. tomato DC3000 (Pst) leads to consistent losses in tomato crops, urging to multiply investigations on the physiological bases for its infectiveness. As other P. syringae pathovars, Pst is equipped with photoreceptors for blue and red light, mimicking the photosensing ability of host plants. In this work we have investigated Pst strains lacking the genes for a blue-light sensing protein (PstLOV), for a bacteriophytochrome (PstBph1) or for heme-oxygenase-1. When grown in culturing medium, all deletion mutants presented a larger growth than wild-type (WT) Pst under all other light conditions, with the exception of blue light which, under our experimental conditions (photon fluence rate = 40 μmol m(-2) s(-1)), completely suppressed the growth of the deletion mutants. Each of the knockout mutants shows stronger virulence towards Arabidopsis thaliana than PstWT, as evidenced by macroscopic damages in the host tissues of infected leaves. Mutated bacteria were also identified in districts distant from the infection site using scanning electron microscopy. These results underscore the importance of Pst photoreceptors in responding to environmental light inputs and the partial protective role that they exert towards host plants during infection, diminishing virulence and invasiveness.

This study investigated the effects of a commercial biofertilizer containing the mycorrhizal fungus Rhizophagus irregularis and the diazotrophic N-fixing bacterium Azotobacter vinelandii on root and shoot growth, yield, and nutrient uptake in common wheat (Triticum aestivum L.) in order to improve the sustainable cultivation of this widespread crop. The trials were carried out in controlled conditions (rhizoboxes) and in open fields over two years to investigate the interaction between inoculation and three doses of nitrogen fertilization (160, 120 and 80 kg ha−1) in a silty-loam soil of the Po Plain (NE Italy). In rhizoboxes, efficient root colonization by R. irregularis was observed at 50 days after sowing with seed inoculation, together with improved root tip density and branching (+~30% vs. controls), while the effects of post-emergence inoculation by soil and foliar spraying were not observable at plant sampling. In the open, field spraying at end tillering significantly increased the volumetric root length density (RLD, +22% vs. controls) and root area density (+18%) after about two months (flowering stage) in both years under medium and high N fertilization doses, but not at the lowest N dose. In absence of inoculation, RLD progressively decreased with increased N doses. Inoculation had a negligible effect on grain yield and N uptake, which followed a typical N dose-response model, while straw Zn, P, and K concentrations were seldom improved. It is concluded that medium-high N fertilization doses are required to achieve the target yield and standards of quality (protein contents) in wheat cultivation, while the use of this mixed VAM-PGPR biofertilizer appears to be a sustainable mean for minimizing the adverse effects of chemical N fertilizers on root expansion and for improving the uptake of low-mobility nutrients, which has potentially relevant environmental benefits.

The adenohypophysial cell types of the adult male freshwater goby Padogobius martensi were identified and localized using histochemical and immunocytochemical techniques. Lactotropes were arranged in an irregular mass which occupied a major portion of the rostral pars distalis (RPD). Lead haematoxylin (PbH) stained the corticotropes selectively. These cells formed large clusters or islets between the neurohypophysial branches penetrating the RPD and the lactotropes. In addition, few isolated or clustered corticotropes were observed in the proximal pars distalis (PPD). Corticotropes showed a moderate immunoreactivity to synthetic anti-human adrenocorticotropic hormone 1-24 but a strong immunoreactivity with antiserum to human a-melanocyte-stimulating hormone, which so far has not been observed in any other teleosts. Of the two mouse monoclonal antibodies to the human thyrotropin b subunit used, one failed to bind the thyrotropes, while the other stained selectively but very weakly cells in the dorsal-anterior part of the proximal pars distalis (PPD) indicating that thyrotropes were probably located in this region. Somatotropes were arranged mainly in a multicellular layer bordering the neurohypophysial processes penetrating the PPD, but some were isolated throughout the PPD. The antiserum to rainbow trout Oncorhynchus mykiss gonadotropin I b subunit bound to gonadotropes located in the central and ventral part of the PPD, and along the external periphery of the pars intermedia (PI). The cells reacting to the antiserum to rainbow trout gonadotropin II b subunit largely showed the same distribution as gonadotropes I, but some were also found isolated or in small clusters between somatolactotropes and melanotropes at the interface PI/neurohypophysis (NH) and throughout the PI, as well as intermingled with thyrotropes in the dorsal-anterior part of the PPD, and with lactotropes and corticotropes in the RPD. These results indicate the presence of two types of both gonadotropins and gonadotropes in P. martensi, but do not exclude some degree of gonadotropin I and gonadotropin II colocalization in the same cells. A distribution of gonadotropes II throughout the adenohypophysis similar to that found in P. martensi has not yet been observed in other teleosts; it suggests the possibility of local interactions between these cells and all the other adenohypophysial cell types. The PI contained somatolactotropes, which were distributed along the neurohypophysial border, and melanotropes which were arranged in clusters mostly located further away from the neural tissue. Melanotropes did not react to PbH and showed positive immunostaining to both anti-human ACTH 1-24 and anti-human a-MSH.