Differential cultivars and molecular markers were used to analyze 59 isolates of the bean anthracnose pathogen, Colletotrichum lindemuthianum, from different regions of Mexico. Ten distinct races were determined, three of which had not been reported previously in Mexico. Isolates were found to infect only a narrow range of the differential cultivars used and were restricted to cultivars of Middle American origin. A comparison of random amplified polymorphic DNA and amplified fragment length polymorphism (AFLP) analyses was carried out on a subset of the fungal isolates. Determination of genetic distances based on AFLP data and production of a dendrogram demonstrated two levels of association: i) isolates classified into two major groups according to the type of cultivar or system of cultivation from which they originated, and ii) isolates could be classified into smaller subgroups generally associated with the geographic location from which they were obtained. Bootstrap analysis and determination of confidence intervals showed these geographic groupings to be extremely robust.

No abstract

Sympathetic neurons have the capability to segregate their neurotransmitters (NTs) and co-transmitters to separate varicosities of single axons; furthermore, in culture, these neurons can even segregate classical transmitters. In vivo sympathetic neurons employ acetylcholine (ACh) and other classical NTs such as gamma aminobutyric acid (GABA). Herein, we explore whether these neurons in vivo segregate these classical NTs in the superior cervical ganglia of the rat. We determined the topographical distribution of GABAergic varicosities, somatic GABAA receptor, as well as the regional distribution of the segregation of ACh and GABA. We evaluated possible regional differences in efficacy of ganglionic synaptic transmission, in the sensitivity of GABAA receptor to GABA and to the competitive antagonist picrotoxin (PTX). We found that sympathetic preganglionic neurons in vivo do segregate ACh and GABA. GABAergic varicosities and GABAA receptor expression showed a rostro-caudal gradient along ganglia; in contrast, segregation exhibited a caudo-rostral gradient. These uneven regional distributions in expression of GABA, GABAA receptors, and level of segregation correlate with stronger synaptic transmission found in the caudal region. Accordingly, GABAA receptors of rostral region showed larger sensitivity to GABA and PTX. These results suggest the presence of different types of GABAA receptors in each region that result in a different regional levels of endogenous GABA inhibition. Finally, we discuss a possible correlation of these different levels of GABA modulation and the function of the target organs innervated by rostral and caudal ganglionic neurons.

Helianthus petiolaris (Asteraceae) native to North America has naturalized in Argentina. The extensive overlapping with sunflower crop regions, the coincidence of life cycles and the common pollinators facilitate interspecific crosses with sunflower, H. annuus var. macrocarpus. To estimate the occurrence of crop-to-wild and wild-to-crop gene flow, off-type plants in progenies of pure stands of both species flowering in coincidence and the presence of crop alleles in H. petiolaris populations were investigated in 26 wild populations and nine crop fields. Morphological traits and RAPD markers were used to attempt hybrid characterization. Off-type individuals were found in frequencies of 0.5 and 0.3% among crop progenies and wild populations, respectively. Off-type plants showed intermediate values for metric morphological traits and low fertility traits. Some off-type plants proved to carry crop alleles based on molecular analysis. The average frequency of cultivar-marker introgression across the wild populations was very low (0.02). Although observed hybridization rates seem to be low, the extension of crop-wild overlapping in Argentina make hybrid formation a noticeable process. Therefore, the new sunflower varieties and eventually GM varieties would transfer their traits through pollen flow and they would persist in H. petiolaris populations.

The glutamine synthetase and the NADP-specific glutamate dehydrogenase activities of Neurospora crassa were lost in a culture without carbon source only when in the presence of air. Glutamine synthetase was previously reported to be liable to in vitro and in vivo inactivation by activated oxygen species. Here we report that NADP-specific glutamate dehydrogenase was remarkably stable in the presence of activated oxygen species but was rendered susceptible to oxidative inactivation when chelated iron was bound to the enzyme and either ascorbate or H202 reacted on the bound iron. This reaction gave rise to further modifications of the enzyme monomers by activated oxygen species, to partial dissociation of the oligomeric structure, and to precipitation and fragmentation of the enzyme. The in vitro oxidation reaction was affected by pH, temperature, and binding to the enzyme of NADPH. Heterogeneity in total charge was observed in the purified and immunoprecipitated enzymes, and the relative amounts of enzyme monomers with different isoelectric points changed with time of the oxidizing reaction.Modification of proteins by activated oxygen species has been identified in various enzymes (5, 13, 14, 17, 20, 26-28, 30, 41, 43, 46, 48, 51). This modification is generally accompanied by changes in catalytic activity, usually inhibiting it (5, 13, 14, 17, 20, 26-28, 41, 43), but there are also examples of enzyme activation mediated by highly reactive oxygen metabolites (30,48,51). Several oxidation systems have been used, including neutrophil oxidative burst (34, 39), enzymatic systems such as cytochrome P-450 (17, 44), and nonenzymatic systems such as the ascorbate model system (27). Modification of proteins by mixed-function oxidation has been found in pathological-related processes associated with oxygen toxocity (45), host defense mechanisms (34), and aging (35). The physiological functions of oxidation by activated oxygen species have not been defined yet, but they may include intracellular proteolysis (8,11,(37)(38)(39)(40) and regulation of anaerobic and aerobic oxidation metabolism (21). We have recently suggested that oxidation of proteins by activated oxygen species is also related to developmental processes in microorganisms (W. Hansberg and J. Aguirre, J. Theor. Biol., in press).Part of our research has focused on the regulation of nitrogen metabolism during germination and conidiation of Neurospora crassa (6,7,19). In the mycelium which forms the aerial hyphae (47), glutamine synthetase (GS) and NADP-specific glutamate dehydrogenase [GDH(NADP)] activities are lost (7). The N. crassa GS is modified in vitro by activated oxygen species (1) in a similar way to that of Escherichia coli GS, in which mixed-function oxidation has been studied in great detail (15,17,(26)(27)(28)32 extract is incubated with reduced NAD or NADP and (ii) when purified GS is incubated with hydrogen peroxide and ferrous iron (Fe2") or with ascorbate and ferric iron (Fe3") in the presence of oxygen (1). The in vitro-oxidized GS is completely...