Biology subjects

Bernardo, R.

Publications and source records attributed to Bernardo, R..

3 recordsLinked to original sources

bioRxiv2019

Assessing by modeling the consequences of increased recombination in genomic selection of Oryza sativa and Brassica rapa.

Recombination generates genetic diversity but the number of crossovers per meiosis is limited in most species. Previous studies showed that increasing recombination can enhance response to selection. However, such studies did not assume a specific method of modifying recombination. Our objective was to test whether two methods used to increase recombination in plants could increase the genetic gain in a population undergoing genomic selection. The first method, in Oryza sativa, used a mutant of anti-crossover genes to increase global recombination without affecting the recombination landscape. The second one uses the ploidy level of a cross between Brassica rapa and Brassica napus to increase the recombination particularly in pericentromeric regions. These recombination landscapes were used to model recombination while quantitative trait loci positions were based on the actual gene distribution. We simulated selection programs with initially a cross between two inbred lines, for two species. Increased recombination enhanced the response to selection. The amount of enhancement in the cumulative gain largely depended on the species and the number of quantitative trait loci (2, 10, 20, 50, 200 or 1000 per chromosome). Genetic gains were increased up to 30% after 20 generations. Furthermore, modifying the recombination landscape was the most effective: the gain was larger by 25% with the first method and 33% with the second one in B. rapa, and 15% compared to 11% in O. sativa. Thus, increased recombination enhances the genetic gain in genomic selection for long-term selection programs, with visible effects after four to five generations.

genetics↗

bioRxiv2019

Predicted genetic gains from introgressing chromosome segments from exotic germplasm into an elite soybean cultivar

Broadening the diversity of cultivated soybean [Glycine max (L.) Merrill] through introgression of exotic germplasm has been difficult. Our objectives were to 1) determine if introgressing specific chromosome segments (instead of quantitative trait locus alleles) from exotic soybean germplasm has potential for improving an elite cultivar, and 2) identify strategies to introgress and pyramid exotic chromosome segments into an elite cultivar. We estimated genomewide marker effects for yield and other traits in seven crosses between the elite line IA3023 and seven soybean plant introductions (PIs). We then predicted genetic gains from having [≤]2 targeted recombinations per linkage group. When introgression was modeled for yield while controlling maturity in the seven PI x IA3023 populations, the predicted yield was 8 to 25% over the yield of IA3023. Correlated changes in maturity, seed traits, lodging, and plant height were generally small but were in the favorable direction. In contrast, selecting the best recombinant inbred (without targeted recombination) in each of the PI x IA3023 populations led to negative or minimal yield gains over IA3023. In one PI x IA3023 population, introgressing and pyramiding only two linkage groups from recombinant inbreds into IA3023 was predicted to achieve an 8% yield gain over IA3023 without sacrificing the performance of other traits. The probability of inheriting intact chromosomes was high enough to allow introgression and pyramiding of chromosome segments in 5-6 generations. Overall, our study suggested that introgressing specific chromosome segments is an effective way to introduce exotic soybean germplasm into an elite cultivar.\n\nKey messageTo improve an elite soybean line, introgress longer chromosome segments instead of QTL alleles from exotic germplasm.

genetics↗

bioRxiv2019

Effect of progesterone on Candida albicans biofilm formation under acidic conditions: a transcriptomic analysis

Vulvovaginal candidiasis (VVC) caused by Candida albicans is a common disease worldwide. A very important C. albicans virulence factor is its ability to form biofilms on epithelium and/or on intrauterine devices promoting VVC. It has been shown that VVC has a hormonal dependency and that progesterone affects virulence traits of C. albicans cells. To understand how the acidic environment (pH 4) and progesterone (either alone and in combination) modulate C. albicans response during formation of biofilm, a transcriptomic analysis was performed together with characterization of the biofilm properties. Compared to planktonic cells, acidic biofilm-cells exhibited major changes in their transcriptome, including modifications in the expression of 286 genes that were not previously associated with biofilm formation in C. albicans. The vast majority of the genes up-regulated in the acidic biofilm cells (including those uniquely identified here) are known targets of Sfl1, and the expression of this regulator impaired formation of the acidic biofilm. Under the acidic conditions used, progesterone treatment reduced C. albicans biofilm biomass, structural cohesion, matrix quantity and susceptibility to fluconazole. Transcriptomic analysis of progesterone-exposed biofilms led to the identification of 65 down-regulated genes including, among others, the regulator Tec1 and several of its target genes suggesting that the function of this transcription factor is inhibited by the presence of the hormone. Overall, the results of this study show that progesterone modulates C. albicans biofilm formation and genomic expression under acidic conditions, which may have implications for C. albicans pathogenicity in the vaginal environment.\n\nAuthor summaryVulvovaginal candidiasis (VVC) is an infection of the vaginal tract that affects millions of women every year. It is caused by fungi of the genus Candida, mainly Candida albicans. Several C. albicans virulence factors contribute to the establishment of this infection, including the ability to form biofilms on vaginal walls and intrauterine devices. Candida species belong to vaginal microflora, however under certain conditions they can cause infection. It has been shown that conditions that prompt VVC include those leading to high progesterone levels, as pregnancy. Here we show that progesterone impairs the ability of C. albicans cells to form biofilms but causes a potential protective stress response. Indeed, we reveal an increased fluconazole resistance of biofilm cells grown in the presence of the hormone. Additionally, our results suggest that biofilm cells have a specific response to acidic conditions, as those established in the vaginal environment. Deepening the knowledge on the modulation of C. albicans virulence by vaginal conditions is essential for a full understanding of the pathogenesis of this species in the vaginal tract and contribute to the disclosure of new targets to treat VVC.

microbiology↗