The suggestion that brassinosteroids (BRs) have a negative regulatory role in de-etiolation is based largely on correlative evidence, which includes the de-etiolated phenotypes of, and increased expression of light-regulated genes in, dark-grown mutants defective in BR biosynthesis or response. However, we have obtained the first direct evidence which shows that endogenous BR levels in light-grown pea seedlings are increased, not decreased, in comparison with those grown in the dark. Similarly, we found no evidence of a decrease in castasterone (CS) levels in seedlings that were transferred from the dark to the light for 24 h. Furthermore, CS levels in the constitutively de-etiolated lip1 mutant are similar to those in wild-type plants, and are not reduced as is the case in the BR-deficient lkb plants. Unlike lip1, the pea BR-deficient mutants lk and lkb are not de-etiolated at the morphological or molecular level, as they exhibit neither a de-etiolated phenotype or altered expression of light-regulated genes when grown in the dark. Similarly, dark-grown WT plants treated with the BR biosynthesis inhibitor, Brz, do not exhibit a de-etiolated phenotype. In addition, analysis of the lip1lkb double mutant revealed an additive phenotype indicative of the two genes acting in independent pathways. Together these results strongly suggest that BR levels do not play a negative-regulatory role in de-etiolation in pea.
BackgroundDespite a high genetic similarity to peach, almonds (Prunus dulcis) have a fleshless fruit and edible kernel, produced as a crop for human consumption. While the release of peach genome v1.0 provides an excellent opportunity for almond genetic and genomic studies, well-assessed segregating populations and the respective saturated genetic linkage maps lay the foundation for such studies to be completed in almond.ResultsUsing an almond intraspecific cross between 'Nonpareil' and 'Lauranne' (N × L), we constructed a moderately saturated map with SSRs, SNPs, ISSRs and RAPDs. The N × L map covered 591.4 cM of the genome with 157 loci. The average marker distance of the map was 4.0 cM. The map displayed high synteny and colinearity with the Prunus T × E reference map in all eight linkage groups (G1-G8). The positions of 14 mapped gene-anchored SNPs corresponded approximately with the positions of homologous sequences in the peach genome v1.0. Analysis of Mendelian segregation ratios showed that 17.9% of markers had significantly skewed genotype ratios at the level of P < 0.05. Due to the large number of skewed markers in the linkage group 7, the potential existence of deleterious gene(s) was assessed in the group. Integrated maps produced by two different mapping methods using JoinMap® 3 were compared, and their high degree of similarity was evident despite the positional inconsistency of a few markers.ConclusionsWe presented a moderately saturated Australian almond map, which is highly syntenic and collinear with the Prunus reference map and peach genome V1.0. Therefore, the well-assessed almond population reported here can be used to investigate the traits of interest under Australian growing conditions, and provides more information on the almond genome for the international community.
We report sequence, tissue expression and map-position data for myogenin, MYOD1, myostatin and follistatin in three Ictalurid catfish species: channel catfish (Ictalurus punctatus), blue catfish (I. furcatus) and white catfish (Ameiurus catus). These genes are involved in muscle growth and development in mammals and may play similar roles in catfish. Amino acid sequences were highly conserved among the three Ictalurid species (>95% identity), moderately conserved among catfish and zebrafish (approximately 80% identity), and less conserved among catfish and humans (approximately 40-60% identity) for all four genes. Gene structure (number of exons and introns and exon-intron boundaries) was conserved between catfish and other species for all genes. Myogenin and MYOD1 expression was limited to skeletal muscle in juvenile channel catfish, similar to expression patterns for these genes in other fish and mammalian species. Myostatin was expressed in a variety of tissues in juvenile channel catfish, a pattern common in other fish species but contrasting with data from mammals where myostatin is primarily expressed in skeletal muscle. Follistatin was expressed in juvenile catfish heart, testes and spleen. All four genes contained polymorphic microsatellite repeats in non-coding regions and linkage analysis based on inheritance of these microsatellite loci was used to place the genes on the channel catfish linkage map. Information provided in this study will be useful in further studies to determine the role these genes play in muscle growth and development in catfish.
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