Estimation of outcrossing rate in a breeding population of Eucalyptus urophylla with dominant RAPD and AFLP markers

Eucalyptus breeding is typically conducted by selection in open-pollinated progenies. As mating is controlled only on the female side of the cross, knowledge of outcrossing versus selling rates is essential for maintaining adequate levels of genetic variability for continuous gains. Outcrossing rate in an open-pollinated breeding population of Eucalyptus urophylla was estimated by two PCR-based dominant marker technologies, RAPD and AFLP, using 11 open-pollinated progeny arrays of 24 individuals. Estimated outcrossing rates indicate predominant outcrossing and suggest maintenance of adequate genetic variability within families. The multilcous outcrossing rate (t(m)) estimated from RAPD markers (0.93 +/- 0.027), although in the same range, was higher (alpha > 0.01) than the estimate based on AFLP (0.89 +/- 0.033). Both estimates were of similar magnitude to those estimated for natural populations using isozymes. The estimated Wright's fixation index was lower than expected based on t, possibly resulting from selection against selfed seedlings when sampling plants for the study. An empirical analysis suggests that 18 is the minimum number of dominant marker loci necessary to achieve robust estimates of t,. This study demonstrates the usefulness of dominant markers, both RAPD and AFLP, for estimating the outcrossing rate in breeding and natural populations of forest trees. We anticipate an increasing use of such PCR-based technologies in mating-system studies, in view of their high throughput and universality of the reagents, particularly for species where isozyme systems have not yet been optimized.

Identification of sex in Carica papaya L. using RAPD markers

Brazil is currently the worlds largest producer of papaya (Carica papaya L.), producing fruits for both the domestic market and export. Only fruits from hermaphrodite plants are marketed because they have the necessary commercial characteristics, i.e. they are pear-shaped and have thicker flesh and a smaller internal cavity. Increased papaya yield has been limited mainly by the ratio of female to hermaphrodite (1:2) plants normally occurring in orchards. This ratio causes great losses to papaya producers and the identification of the sex of seedlings during the nursery stage would be an important advance. In our study random amplified polymorphic DNA (RAPD) analysis was used to differentiate between the sexual forms of three commercial C. papaya cultivars belonging to the Solo group. RAPD assays using the BC210 primer were able to detect hermaphrodites in all of the cultivars tested. The BC210(438)molecular marker was much better at papaya sex differentiation than other markers described in the literature.

The first cytogenetic report of fireflies (Coleoptera, Lampyridae) from Brazilian fauna

The first cytogenetic analysis of fireflies from Brazilian fauna was carried out in this work. The investigation of two species of the subfamily Lampyrinae, Aspisoma maculatum and Photinus sp. (aff. pyralis), showed the diploid number 2n = 19 and an X0 sex determination system in males. These observations are similar to those already described for all the Lampyrinae species previously studied. In contrast, Bicellonycha lividipennis (Photurinae) revealed the karyotype 2n = 16 + neoXY, which has not yet been registered for any firefly species. The neoXY sex determination system encountered in this species probably arose through fusion between an ancestral X sex chromosome, belonging to the X0 system, and an autosomal element. This event also reduced the diploid number from 2n = 19, which is more frequent in the family Lampyridae, to 2n = 18 in B. lividipennis. The analysis of meiotic cells showed that the neoXY sexual bivalent of B. lividipennis exhibited a prominent terminal chiasma, indicating that the sex chromosomes are not wholly differentiated and still retain a region of homology. A review of the cytogenetic data known for the family Lampyridae was also documented in this work, as well as a discussion on the main trends of chromosomal evolution that seem to have occurred in this group.

CYTOGENETIC EVIDENCE OF INVOLVEMENT OF CHROMOSOME REGION-15Q12 AND REGION-12Q15 IN CONDITIONS WITH ASSOCIATED OVERGROWTH

Syndromes with associated overgrowth are poorly understood. Besides their mode of inheritance, nothing is known regarding the basic genetic alterations that lead to their abnormal phenotypic manifestations. The chromosome localization of the genes involved remains unknown for this group of syndromes, with the only exception being the Wiedemann-Beckwith syndrome.

Computer-assisted analysis of cell proliferation markers in oral lesions

Abnormalities in any component of the cell cycle regulatory machine may result in oral. cancer, and markers of cell proliferation have been used to determine the prognosis of tumor progression. The aim of this study was to determine whether silver-stained nucleolar organizer region (AgNOR) and Ki-67 measurements could improve the assessment of growth rates in oral lesions. Eighty-three oral biopsies were studied, 20 of which were classified as fibrous inflammatory hyperplasia (FIH), 40 as leukoplakia (LKP) and 23 as oral. squamous cell carcinoma (OSCC). Within the LKP group, 22 out of 29 biopsies were diagnosed as non-dysplastic leukoplakia (LK) and 18 as dysplastic teukoptakia (DLK), presenting discrete, moderate and severe dysplasia. Ki-67 immunotabeting of the lesions increased steadily in the following order: FIH, DLK, LK and OSCC, indicating that Ki-67 is a good marker for predicting the protiferative fraction among benign, premalignant and malignant oral lesions. The median values of AgNOR parameters indicate that the morphometric index gives better results regarding the proliferative rate than the numerical one. A series of linear regressions between AgNOR parameters and Ki-67 showed positive associations. We conclude that a combination of Ki-67 and morphometric AgNOR analyses could be used as an aid in the determination of the protiferative status of oral epithelial. cells in oral cancer. (C) 2007 Elsevier GmbH. All rights reserved.

Oxytocinergic and serotonergic systems involvement in sodium intake regulation: satiety or hypertonicity markers?

Previous studies demonstrated the inhibitory participation of serotonergic ( 5-HT) and oxytocinergic (OT) neurons on sodium appetite induced by peritoneal dialysis (PD) in rats. The activity of 5-HT neurons increases after PD- induced 2% NaCl intake and decreases after sodium depletion; however, the activity of the OT neurons appears only after PD-induced 2% NaCl intake. To discriminate whether the differential activations of the 5-HT and OT neurons in this model are a consequence of the sodium satiation process or are the result of stimulation caused by the entry to the body of a hypertonic sodium solution during sodium access, we analyzed the number of Fos-5-HT- and Fos-OT-immunoreactive neurons in the dorsal raphe nucleus and the paraventricular nucleus of the hypothalamus-supraoptic nucleus, respectively, after isotonic vs. hypertonic NaCl intake induced by PD. We also studied the OT plasma levels after PD- induced isotonic or hypertonic NaCl intake. Sodium intake induced by PD significantly increased the number of Fos-5- HT cells, independently of the concentration of NaCl consumed. In contrast, the number of Fos-OT neurons increased after hypertonic NaCl intake, in both depleted and nondepleted animals. The OT plasma levels significantly increased only in the PD- induced 2% NaCl intake group in relation to others, showing a synergic effect of both factors. In summary, 5-HT neurons were activated after body sodium status was reestablished, suggesting that this system is activated under conditions of satiety. In terms of the OT system, both OT neural activity and OT plasma levels were increased by the entry of hypertonic NaCl solution during sodium consumption, suggesting that this system is involved in the processing of hyperosmotic signals.

Evaluation of the genetic diversity of Xylella fastidiosa strains from citrus and coffee hosts by single-nucleotide polymorphism markers

The aim of this study was to obtain information about genetic diversity and make some inferences about the relationship of 27 strains of Xylella fastidiosa from different hosts and distinct geographical areas. Single-nucleotide polymorphism (SNP) molecular markers were identified in DNA sequences from 16 distinct regions of the genome of 24 strains of X. fastidiosa from coffee and citrus plants. Among the Brazilian strains, coffee-dependent strains have a greater number of SNPs (10 to 24 SNPs) than the citrus-based strains (2 to 12 SNPs); all the strains were compared with the sequenced strain 9a5c. The identified SNP markers were able to distinguish, for the first time, strains from citrus plants and coffee and showed that strains from coffee present higher genetic diversity than the others. These markers also have proven to be efficient for discriminating strains from the same host obtained from different geographic regions. X. fastidiosa, the causal agent of citrus variegated chlorosis, possesses genetic diversity, and the SNP markers were highly efficient for discriminating genetically close organisms.

CYTOGENETIC ANALYSIS OF THE BRAZILIAN BLIND CATFISH PIMELODELLA-KRONEI AND ITS PRESUMED ANCESTOR, P-TRANSITORIA

Karyotypes of the blind catfish Pimelodella kronei from three different caves in the southwestern part of the State of São Paulo, Brazil, and of its presumed ancestor Pimelodella transitoria were examined. Chromosome number and formula, as well as C-banding pattern and NOR location were found to be the same in both species, supporting the hypothesis of a close relationship and even conspecificity of P. kronei and P. transitoria.