Variability among strains of Aspergillus section Nigri with capacity to degrade tannic acid isolated from extreme environments.

Tannins are polyphenolic compounds that cause astringent flavor and turbidity in food. Tannase is an enzyme that catalyzes the hydrolysis of tannins and is used in food industry. This study was conducted to determine the genetic variability and the tannase alleles variation in fungal strains isolated from soil and plants at five extreme areas of Coahuila, México. Two screening assays under 1 and 20 % of tannic acid were performed, with the isolations. In these assays, it was possible to identify 756 and 128 fungal strains, respectively. The major fungal variability was observed in "Cuatro Ciénegas" with 26 strains. The microorganisms were distributed in 11 groups, which correspond to Aspergillus section Nigri. AN7 and AN1 groups showed the major number of isolates from "Paila" and "Cuatro Ciénegas" locations, respectively. In the last location, the major diversity and specific richness were found. But in "Ojo Caliente," tannase allele conservations were observed.

Transcriptomic landscape of prophase I sunflower male meiocytes.

Meiosis is a form of specialized cell division that generates gametes, allowing recombination of alleles and halving the chromosome number. Arabidopsis and maize are the plant models that have been most extensively studied to determine the genes involved in meiosis. Here we present an RNA-seq study in which gene expression in male meiocytes isolated during prophase I was compared to that in somatic tissues of the sunflower HA89 line. We sampled more than 490 million gene tags from these libraries, assembled them de novo into a sunflower transcriptome. We obtained expression data for 36,304 sunflower genes, of which 19,574 (54%) were differentially expressed (DE) between meiocytes and somatic tissue. We also determined the functional categories and metabolic pathways that are DE in these libraries. As expected, we found large differences between the meiotic and somatic transcriptomes, which is in accordance with previous studies in Arabidopsis and maize. Furthermore, most of the previously implicated meiotic genes were abundantly and DE in meiocytes and a large repertoire of transcription factors (TF) and genes related to silencing are expressed in the sunflower meiocytes. We detected TFs which appear to be exclusively expressed in meiocytes. Our results allow for a better understanding of the conservation and differences in the meiotic transcriptome of plants.

ISH-facilitated analysis of meiotic bivalent pairing.

Chiasmata constitute one of the cornerstones of sexual reproduction in most eukaryotes. They mediate the reciprocal genetic exchange between homologues and are essential to the proper orientation of the homologous centromeres in meiosis I. As markers of recombination, they offer a cytological means of mapping. Rather than trying to accurately count individual chiasmata, we have examined properties of the mathematical relationship between frequencies of nonadorned disomic configurations in meiosis (ring, rods, and univalents) and the probabilities at which arms of the respective chromosomes are chiasmate (one or more chiasma per arm). Numerical analyses indicated that conventionally analyzed bivalents with nonidentified arms yield statistically biased estimates of chiasma probabilities under a broad range of circumstances. We subsequently analyzed estimators derived from adorned configurations with ISH-marked arms, which were found to be statistically far superior, and with no assumptions concerning interference across the centromere. We applied this methodology in the study of chromosomes 16 and 23 of cotton (Gossypium hirsutum), and estimated their arm lengths in centimorgans. The results for chromosome 23, the only one of the two chromosomes with a documented RFLP map, were consistent with the literature. Similar molecular-meiotic configuration analyses can be used for a wide variety of eukaryotic organisms and purposes: for example, providing far more powerful meiotic comparisons of genomes of chromosomes, and a rapid means of evaluating effects on recombination. Key words : meiotic configurations, chiasma frequencies, in situ hybridization, cotton.

A maximum likelihood algorithm for genome mapping of cytogenetic loci from meiotic configuration data.

Frequencies of meiotic configurations in cytogenetic stocks are dependent on chiasma frequencies in segments defined by centromeres, breakpoints, and telomeres. The expectation maximization algorithm is proposed as a general method to perform maximum likelihood estimations of the chiasma frequencies in the intervals between such locations. The estimates can be translated via mapping functions into genetic maps of cytogenetic landmarks. One set of observational data was analyzed to exemplify application of these methods, results of which were largely concordant with other comparable data. The method was also tested by Monte Carlo simulation of frequencies of meiotic configurations from a monotelodisomic translocation heterozygote, assuming six different sample sizes. The estimate averages were always close to the values given initially to the parameters. The maximum likelihood estimation procedures can be extended readily to other kinds of cytogenetic stocks and allow the pooling of diverse cytogenetic data to collectively estimate lengths of segments, arms, and chromosomes.