Background: In western Mexico, the Magnolia pacifica complex includes three morphologically defined, endemic and, endangered species, distributed along a 215 km continentality and moisture gradient: Magnolia pugana, M. pacifica s.s., and M. vallartensis.
Hypothesis: Genetic evidence supports the taxonomical classification of the M. pacifica complex.
Study site and dates: Western Mexico, samples were collected in 2012-2015.
Methods: Six Inter-Simple Sequence Repeats (ISSR) primers amplified 76 clear and reproducible fragments in 278 individuals from 10 localities representative of the M. pacifica complex. ISSR dataset was analyzed using STRUCTURE 2.3.4, UPGMA clustering, Barrier 2.2, and AMOVA. Genetic diversity parameters were also estimated.
Results: Genetic analyses revealed two main groups: M. pugana and M. pacifica s.s.–M. vallartensis. Two subpopulations within each group were evidenced, particularly M. pacifica s.s. was separated from M. vallartensis. Geographical barriers to gene flow were identified. AMOVA revealed a similar and significant proportion of variation between and within groups. M. pugana has lower genetic diversity and higher differentiation than the M. pacifica s.s-M. vallartensis group.
Conclusions: Our results support the recognition of M. pugana as a genetically distinct lineage from M. pacifica s.s and M. vallartensis, but did not reveal a clear species boundary between the last two taxa. Geographical barriers and distance isolation might explain the genetic structure and differentiation pattern within the M. pacifica s.s. species complex. All main groups and subgroups defined in this study should be considered as separate conservation units, and concerted efforts are needed to protect them.
The administration of probiotics is a promising approach to reduce the prevalence of colon cancer, a multifactorial disease, with hereditary factors, as well as environmental lifestyle-related risk factors. Biogenic polyamines, putrescine, spermidine, and spermine are small cationic molecules with great roles in cell proliferation and differentiation as well as regulation of gene expression. Ornithine decarboxylase is the first rate-limiting enzyme for polyamine synthesis, and upregulation of ornithine decarboxylase activity and polyamine metabolism has been associated with abnormal cell proliferation. This paper is focused on studying the protective role of Lactobacillus casei ATCC 393 in a chemically induced mouse model of colon carcinogenesis, directing our attention on aberrant crypt foci as preneoplastic markers, and on polyamine metabolism as a possible key player in carcinogenesis. BALB/c mice were administered 1,2-dimethylhydrazine dihydrochloride (DMH) to induce colon cancer (20 mg/kg body weight, subcutaneous, twice a week for 24 weeks). L. casei ATCC 393 was given orally (10 CFU, twice a week), 2 weeks before DMH administration. Hematoxylin and eosin staining, high-performance liquid chromatography, and Western blotting were used to evaluate aberrant crypt foci, urinary polyamines, and ornithine decarboxylase expression in the colon. The experimental data showed that the preventive administration of L. casei ATCC 393 may delay the onset of cancer as it significantly reduced the number of DMH-induced aberrant crypt foci, the levels of putrescine, and the expression of ornithine decarboxylase. Hence, this probiotic strain has a prospective role in protection against colon carcinogenesis, and its antimutagenic activity may be associated with the maintenance of polyamine metabolism.
Ferocactus histrix is a barrel cactus that is widespread in Mexico. A population located inLlanos de Ojuelos, a semiarid zone representative of many disturbed regions in northcentral Mexico, was studied. Over a period of 10 years (1997 to 2007), the average number of individuals decreased from 21.95 to 3.53 plants per 300 m 2 . A change in population size structure was also registered over this period of time. In 2008, a plot selected on the basis of plant abundance was established within the population and a genetic analysis was conducted with ISTR and ISSR markers. This analysis revealed low levels of genetic diversity (expected heterozygosity (HE) = 0.073, Shannon index (I) = 0.113 and HE = 0.178, I = 0.271, respectively) compared with those of most studied cacti species. The genetic diversity between the different life stages was also evaluated, and a gradual decrease in levels of genetic variation was observed from adults to juveniles and seedlings ( HE = 0.130, I = 0.192 to HE = 0.103, I = 0.157). These differences, however, were not significant. Loci fixation and a decrease in the frequency of rare alleles were observed in seedling and juvenile classes. The decline in genetic variation may be associated with recent bottlenecks experienced by the population of F. histrix. If the sizes of local populations of F. histrix continue to decrease, genetic variation will be gradually lost, and the risk of extinction will increase.
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