In vitro culture and micropropagation of the Baetic-Moroccan endemic plant Lapiedra martinezii Lag. (Amaryllidaceae)

Lapiedra martinezii Lag. is a potential medicinal and ornamental plant facing conservation challenges. Thus, this study was focused on determining the conditions for culture initiation and propagation using in vitro techniques. The optimal sterilization procedure combined thermotherapy at 54°C for 60 min and immersion in 7% (w/v) Ca(ClO)₂ solution for 20 min. The most suitable medium to initiate bulb scales cultures was Gamborg B5 medium containing 500 mg L⁻¹ casein, 2 mg L⁻¹ adenine, 10 mg L⁻¹ glutathione and 10 g L⁻¹ sucrose. The most productive multiplication medium tested was Murashige and Skoog medium containing 30 g L⁻¹ sucrose, 4.0 mg L⁻¹ 6-benzylaminopurine, and 0.12 mg L⁻¹ 1-naphtaleneacetic acid. Most plants developed in vitro rooted spontaneously in the multiplication phase. The vast majority of the plants (89%) were successfully transferred to ex vitro conditions, and 100% survived over 1 yr of cultivation outdoors. Sucrose at a concentration of 60 g L⁻¹ was the most effective treatment to increase the biomass of bulblets. High auxin/cytokinin ratios produced the highest callus induction efficiency. The vast majority of callus developed in dark conditions, but none regenerated in the combinations of growth regulators previously tested. The plants obtained by micropropagation did not show significant differences in morphometric traits compared with the wild specimens, which supported the stability of the materials produced in vitro. This is the first report on cell cultures and micropropagation of L. martinezii, and the results can be applied to other Amaryllidaceae for industrial or conservation purposes.

     

Multidate,multisensor remote sensing reveals high density of carbon‐rich mountain peatlands in the páramo of Ecuador

Tropical peatlands store a significant portion of the global soil carbon (C) pool. However, tropical mountain peatlands contain extensive peat soils that have yet to be mapped or included in global C estimates. This lack of data hinders our ability to inform policy and apply sustainable management practices to these peatlands that are experiencing unprecedented high rates of land use and land cover change. Rapid large‐scale mapping activities are urgently needed to quantify tropical wetland extent and rate of degradation. We tested a combination of multidate, multisensor radar and optical imagery (Landsat TM/PALSAR/RADARSAT‐1/TPI image stack) for detecting peatlands in a 2715 km² area in the high elevation mountains of the Ecuadorian páramo. The map was combined with an extensive soil coring data set to produce the first estimate of regional peatland soil C storage in the páramo. Our map displayed a high coverage of peatlands (614 km²) containing an estimated 128.2 ± 9.1 Tg of peatland belowground soil C within the mapping area. Scaling‐up to the country level, páramo peatlands likely represent less than 1% of the total land area of Ecuador but could contain as much as ~23% of the above‐ and belowground vegetation C stocks in Ecuadorian forests. These mapping approaches provide an essential methodological improvement applicable to mountain peatlands across the globe, facilitating mapping efforts in support of effective policy and sustainable management, including national and global C accounting and C management efforts.     

Transgenic Rice Plants Expressing the Antifungal AFP Protein from Aspergillus Giganteus Show Enhanced Resistance to the Rice Blast Fungus Magnaporthe Grisea

The Aspergillus giganteus antifungal protein (AFP), encoded by the afp gene, has been reported to possess in vitro antifungal activity against various economically important fungal pathogens, including the rice blast fungus Magnaporthe grisea. In this study, transgenic rice ( Oryza sativa ) constitutively expressing the afp gene was generated by Agrobacterium -mediated transformation. Two different DNA constructs containing either the afp cDNA sequence from Aspergillus or a chemically synthesized codon-optimized afp gene were introduced into rice plants. In both cases, the DNA region encoding the signal sequence from the tobacco AP24 gene was N-terminally fused to the coding sequence of the mature AFP protein. Transgenic rice plants showed stable integration and inheritance of the transgene. No effect on plant morphology was observed in the afp -expressing rice lines. The inhibitory activity of protein extracts prepared from leaves of afp plants on the in vitro growth of M. grisea indicated that the AFP protein produced by the trangenic rice plants was biologically active. Several of the T(2) homozygous afp lines were challenged with M. grisea in a detached leaf infection assay. Transformants exhibited resistance to rice blast at various levels. Altogether, the results presented here indicate that AFP can be functionally expressed in rice plants for protection against the rice blast fungus M. grisea.     

The GABAA receptor complex in the developing chick optic tectum: characterization of benzodiazepine and ionophore-linked convulsant/barbiturate recognition sites

By use of membrane preparations and incubation conditions optimized for each binding site, we have characterized the benzodiazepine and ionophore-linked-convulsant/barbiturate modulatory sites within the chick tectal GABA_A receptor complex. Using [³H]flunitrazepam (FNZ) and [³⁵S]t-butylbicyclophosphorothionate (TBPS), respectively, as specific radioligand probes for the two sites, we have found in each case one single population of high-affinity, saturable, specific binding sites. The apparent dissociation constants (K_d) show no change during tectal development (9 nM for [³H]FNZ, and 25–28 nM for [³⁵S]TBPS) while the respective densities of binding sites at saturation (B_max) experience in both cases a twofold increase between embryonic day 16 and postnatal day 10. Ligand-specific pharmacological profiles and allosteric interactions between the transmitter and modulatory sites appear to be well preserved in the chick tectal membrane preparations employed in this study.     

Static and dynamic properties of gravity-sensitive receptors in the cat vestibular system

Summary The spike activity of eighth cranial nerve units tonically responsive to head position was recorded in cats anesthetized with pentobarbital sodium, and related with linear accelerations induced by gravity during maintained positions and during dynamic trajectories achieved through rolling around a rostro-caudal axis.The steady-state discharge of 80% of the cells had relatively small coefficients of variation, narrow histograms and periodic autocorrelograms. That of most remaining cells had large coefficients variation, nearly exponential histograms and flat or weakly periodic autocorrelograms.The static relation between head position and discharge showed that each cell had directional sensitivity, i.e. a characteristic change associated with each movement sense. Sixty-six percent of the cells had side-up increases in interval mean and standard deviation, with translation of the histogram to the right and reduction in the average autocorrelogram value: 34% had the opposite relations. Many cells showed multivaluedness, i.e. the interval mean (and other statistics) from different stations at any given position covered a range greater than that at each station. Multivaluedness varied from cell to cell.In the dynamic experiments the discharge was recorded during a continuous motion that involved a single sine wave or a mixture of sinusoids at frequencies up to 0.1 Hz. The spike trains exhibited a continuous mapping of the time varying tilt angle into the instantaneous rate with little or no evidence of multivaluedness. In addition to a tonic part, responses showed a phasic component with the characteristics of a unidirectional rate sensitivity that determined a phase-lead of the response with respect to the stimulus. The relative proportions of tonic and phasic components varied from cell to cell.Based upon anatomical and mechanical considerations (see Appendix) and upon the present results it is suggested that deformations of the trampoline-like membrane occur in a distributed manner. Multivaluedness may be due to forces which, like stiction, prevent complete relaxation of the membrane under static but not under dynamic conditions. The phasic response, whose origin is obscure, argues in favor of the otolithic receptors having a dynamic function, in addition to their role in detecting head positions with respect to gravity.     

Pathogen-induced production of the antifungal AFP protein from Aspergillus giganteus confers resistance to the blast fungus Magnaporthe grisea in transgenic rice

Rice blast, caused by Magnaporthe grisea, is the most important fungal disease of cultivated rice worldwide. We have developed a strategy for creating disease resistance to M. grisea whereby pathogen-induced expression of the afp (antifungal protein) gene from Aspergillus giganteus occurs in transgenic rice plants. Here, we evaluated the activity of the promoters from three maize pathogenesis-related (PR) genes, ZmPR4, mpi, and PRms, in transgenic rice. Chimeric gene fusions were prepared between the maize promoters and the beta-glucuronidase reporter gene (gus A). Histochemical assays of GUS activity in transgenic rice revealed that the ZmPR4 promoter is strongly induced in response to fungal infection, treatment with fungal elicitors, and mechanical wounding. The ZmPR4 promoter is not active in the seed endosperm. The mpi promoter also proved responsiveness to fungal infection and wounding but not to treatment with elicitors. In contrast, no activity of the PRms promoter in leaves of transgenic rice was observed. Transgenic plants expressing the afp gene under the control of the ZmPR4 promoter were generated. Transformants showed resistance to M. grisea at various levels. Our results suggest that pathogen-inducible expression of the afp gene in rice plants may be a practical way for protection against the blast fungus. Most agricultural crop species suffer from a vast array of fungal diseases that cause severe yield losses all over the world. Rice blast, caused by the fungus Magnaporthe grisea (Herbert) Barr (anamorph Pyricularia grisea), is the most devastating disease of cultivated rice (Oryza sativa L.), due to its