RESUMO
One hundred and thirty-five microsatellite markers were developed for hop Humulus lupulus L. from di- and trinucleotide-enriched libraries. Seventy-eight primers showed amplification in two tested genotypes. Twenty-four loci were further characterized on a population of 34 hop samples and the number of alleles per locus, observed heterozygosity and expected heterozygosity ranged from two to 20 (9.7 on average), from 0.0294 to 0.9412 (0.6234 on average) and from 0.0294 to 0.9170 (0.6720 on average), respectively. These microsatellite markers will be further used for studying population structures and relationships and for identifying important qualitative and quantitative loci of hop.
RESUMO
A specific form of gene silencing that was observed visually as a mosaic distribution of fluorescent and non-fluorescent cells apparently dispersed at random within tissues was found in a few green fluorescent protein (GFP)-transformed tobacco lines. To characterize this event quantitatively, we studied flow cytometric measurements in GFP-expressing and -silenced cells in T1 and T2 progeny of four selected plants. The proportion of silenced cells varied considerably among the T1 lines but with notable genotype differences. Mosaic expression was inherited into the T2 generation in which the majority of progenies tested exhibited a level of silencing similar to that of their T1 parental plants. However, in some T2 progenies segregation, evident as a decrease or increase in the proportion of fluorescent cells, was observed. We discuss several factors, such as copy number, promoter activity or polyploidy, that may be the possible causes of the gene silencing, but none sufficiently explain the appearance of the mosaic distribution.