Universidad Autónoma Agraria Antonio Narro

About: Universidad Autónoma Agraria Antonio Narro is a education organization based out in Saltillo, Mexico. It is known for research contribution in the topics: Population & Markov decision process. The organization has 1427 authors who have published 1832 publications receiving 15999 citations.

A study of allelic diversity underlying flowering-time adaptation in maize landraces

Abstract: Landraces (traditional varieties) of domesticated species preserve useful genetic variation, yet they remain untapped due to the genetic linkage between the few useful alleles and hundreds of undesirable alleles. We integrated two approaches to characterize the diversity of 4,471 maize landraces. First, we mapped genomic regions controlling latitudinal and altitudinal adaptation and identified 1,498 genes. Second, we used F-one association mapping (FOAM) to map the genes that control flowering time, across 22 environments, and identified 1,005 genes. In total, we found that 61.4% of the single-nucleotide polymorphisms (SNPs) associated with altitude were also associated with flowering time. More than half of the SNPs associated with altitude were within large structural variants (inversions, centromeres and pericentromeric regions). The combined mapping results indicate that although floral regulatory network genes contribute substantially to field variation, over 90% of the contributing genes probably have indirect effects. Our dual strategy can be used to harness the landrace diversity of plants and animals.

Evidence That Melatonin Acts in the Premammillary Hypothalamic Area to Control Reproduction in the Ewe: Presence of Binding Sites and Stimulation of Luteinizing Hormone Secretion by in Situ Microimplant Delivery

Abstract: Melatonin transduces the effect of day length on LH secretion by acting on the hypothalamus. However, the precise hypothalamic site is unknown. Two studies were undertaken to clarify where melatonin acts in the hypothalamus. Using autoradiographic methods, the hypothalami of 5 ewes were screened to determine whether specific regional densities in melatonin binding existed. A higher density of binding was observed in the premammillary area of the hypothalamus (PMH) (3- to 5-fold higher than the rest of the hypothalamus). This binding area is delimited rostrally by the infundibular recess, caudally by the mammillary bodies, dorsally by the fornix, and ventrally by the base of the brain; and it encompasses the premammillary and tuberomammillary nuclei. To test the functional importance of the identified area, 3 groups of animals received bilateral melatonin microimplants: 1) in the PMH (n = 11); 2) in the anterior/mediobasal hypothalamus (AH/MBH; n = 8); and 3) sham-operated animals received empty microimplants in the PMH (SHAM; n = 6). All ewes were ovariectomized and treated s.c. with a 20-mm SILASTIC brand capsule of estradiol and exposed to long days (16-h light, 8-h dark). At the end of the 80-day experiment, no animal of the SHAM group and only 2 of the 8 ewes of the AH/MBH group displayed a stimulation of LH secretion. In contrast, melatonin implanted in the PMH stimulated LH secretion in 10 of the 11 ewes on day 44.5 +/- 5.3 (mean +/- SEM). ANOVA revealed that the changes in LH secretion were not different between the SHAM and the AH/MBH groups but the PMH group differed from the other 2 groups (P < 0.0001). This study suggests that the PMH is an important target for melatonin to regulate reproductive activity.