M. G. Pereira

Optimizing the efficiency of the touchdown technique for detecting inter-simple sequence repeat markers in corn (Zea mays)

We evaluated the efficiency of the touchdown method to determine the ideal PCR conditions for distinct inter-simple sequence repeat primers for processing DNA from common corn, popcorn, sweet corn, and a Tripsacum-maize hybrid. Genomic DNA was extracted from eight accessions of corn: two of the dent type, one Tripsacum-maize hybrid, one sweet corn, one flint-type corn, and three popcorn. Fifteen inter-simple sequence repeat primers were used: (CT)(8)RC, (CT)(8)TG, (GA)(8)T, (GA)(8)YC, (CTC)(5)RC, (GTC)(6), (GA)(6)CC, (GT)(6)CC, (CAC)(3)GC, (AG)(8)YT, (AC)(8)T, (AC)(8)YG, (CT)(8)RG, (GGAT)(3)GA, and (GAA)(6)AA. The annealing temperature and the melting temperature for each primer were estimated using a formula for RW Genes products, or we used the temperatures indicated by the manufacturer (Invitrogen). The touchdown method was then applied to each primer, varying the number of final cycles (10 or 12) and the decrease in temperature (0.5 degrees or 1.0 degrees C intervals). The gels were compared, considering the revelation quality, band sharpness and the number of bands visualized. The touchdown-PCR method was more efficient for band amplification for most of the primers, especially at higher annealing temperatures. This type of system is useful for reducing the resources, time and effort needed for optimizing temperature conditions for a group of representative primers.

Methodological Improvements on Extraction of Nuclear Proteins and Its Preliminary Analysis During the Maize (Zea mays L.) Endosperm Development

A procedure to obtain endosperm protein extracts was standardized. After confirming the enrichment with nuclear proteins by immunodetection, the protein profiles of extracts from different seed development stages were compared by SDS-PAGE that showed the existence of several differentially expressed proteins.

Edaphic arthropods in different successional stages of Atlantic forest and abandoned.

The vegetation may modifies the structure and composition of the community of edaphic arthropods. This study aimed to compare the community of edaphic arthropods in four areas of abandoned pasture (AP1, AP2, AP3, AP4) and four secondary native forest fragments in a successional gradient (FF1, FF2, FF3, FF4), in Itaborai, Rio de Janeiro, Brazil. The areas are positioned on the hillside and the sampling was conducted in transects outlined in a toposequence (upper, middle and lower sections), where pitfall traps were installed in the dry season. The organisms were identified in taxonomic groups (class, order and family). Comparing the averages for AP and FF, there was no defined pattern in terms of the response of structural attributes (total abundance, richness, uniformity and diversity). Among the areas of FF, higher values of all of the structural attributes occurred in the intermediate stages of forest succession (FF2, FF3), compared to the initial (FF1) and advanced stages (FF4). On average for the FF, the most favored groups were Archaeognatha, Coleoptera, Entomobryomorpha, Pseudoscorpionida, Psocoptera and Symphypleona. On average for the areas of AP, the most favored groups were Acari, Araneae, Formicidae, Diplopoda and Auchenorrhyncha. Among the areas of FF, Sternorryncha, Symphyla and Thysanura were favored in FF1, while Coleoptera, Psocoptera, Pseudoscorpionida, Entomobryomorpha and Archaeognatha were favored in the other successional stages (FF2, FF3, FF4

Genetic-molecular characterization of backcross generations for sexual conversion in papaya (Carica papaya L.).

The low number of improved cultivars limits the expansion of the papaya crop, particularly because of the time required for the development of new varieties using classical procedures. Molecular techniques associated with conventional procedures accelerate this process and allow targeted improvements. Thus, we used microsatellite markers to perform genetic-molecular characterization of papaya genotypes obtained from 3 backcross generations to monitor the inbreeding level and parental genome proportion in the evaluated genotypes. Based on the analysis of 20 microsatellite loci, 77 genotypes were evaluated, 25 of each generation of the backcross program as well as the parental genotypes. The markers analyzed were identified in 11 of the 12 linkage groups established for papaya, ranging from 1 to 4 per linkage group. The average values for the inbreeding coefficient were 0.88 (BC1S4), 0.47 (BC2S3), and 0.63 (BC3S2). Genomic analysis revealed average values of the recurrent parent genome of 82.7% in BC3S2, 64.4% in BC1S4, and 63.9% in BC2S3. Neither the inbreeding level nor the genomic proportions completely followed the expected average values. This demonstrates the significance of molecular analysis when examining different genotype values, given the importance of such information for selection processes in breeding programs.