Frequency analyses of active NORs in nuclei of artificially induced triploid fishes

Effects of Preharvest Methyl Jasmonate and Salicylic Acid Treatments on Growth, Quality, Volatile Components, and Antioxidant Systems of Chinese Chives

Methyl jasmonate (MeJA) and salicylic acid (SA) regulate the production of biologically active compounds in plants and stimulate the accumulation of plant aromatic substances. However, the underlying mechanisms of how MeJA and SA influence characteristic flavor compounds and the antioxidant activity of vegetables are poorly understood. Five MeJA and SA concentrations were used to investigate the dose-dependent effects of these phytohormones on the dry and fresh weight; chlorophyll abundance; the contents of vitamin C, soluble protein, and sugar, nitrate, total phenols, flavonoids, volatile components, and enzymatically produced pyruvic acid; and antioxidant activity in Chinese chive. We found that MeJA and SA at concentrations of 500 and 150 μM, respectively, significantly increased the levels of total chlorophyll, phenols and flavonoids, vitamin C, and volatile components and significantly reduced the accumulation of nitrate. In addition, compared with the control, 500 μM of MeJA significantly increased the soluble sugar and protein content, and 150 μM SA significantly increased the dry and fresh weight of Chinese chive. Furthermore, these concentrations of MeJA and SA significantly increased the enzymatic pyruvate content and the amount of sulfide and aromatic volatile compounds and improved the characteristic flavor compounds. The 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity, Trolox-equivalent antioxidant capacity, and ferric-reducing antioxidant capacity were significantly improved after a preharvest treatment with 500 μM MeJA and 150 μM SA, which could improve the antioxidant activity, thus improving the postharvest quality and preservation characteristics of Chinese chives. Taken together, a preharvest treatment with 500 μM MeJA and 150 μM SA is optimal to improve the growth, quality, antioxidant activity, and flavor of Chinese chive, thereby enhancing its commercial value.

Dynamics of tandemly repeated DNA sequences during evolution of diploid and tetraploid botiid loaches (Teleostei: Cobitoidea: Botiidae)

Polyploidization has played an important role in the evolution of vertebrates, particularly at the base of Teleostei-an enormously successful ray-finned fish group with additional genome doublings on lower taxonomic levels. The investigation of post-polyploid genome dynamics might provide important clues about the evolution and ecology of respective species and can help to decipher the role of polyploidy per se on speciation. Few studies have attempted to investigate the dynamics of repetitive DNA sequences in the post-polyploid genome using molecular cytogenetic tools in fishes, though recent efforts demonstrated their usefulness. The demonstrably monophyletic freshwater loach family Botiidae, branching to evolutionary diploid and tetraploid lineages separated >25 Mya, offers a suited model group for comparing the long-term repetitive DNA evolution. For this, we integrated phylogenetic analyses with cytogenetical survey involving Giemsa- and Chromomycin A3 (CMA3)/DAPI stainings and fluorescence in situ hybridization with 5S/45S rDNA, U2 snDNA and telomeric probes in representative sample of 12 botiid species. The karyotypes of all diploids were composed of 2n = 50 chromosomes, while majority of tetraploids had 2n = 4x = 100, with only subtle interspecific karyotype differences. The exceptional karyotype of Botia dario (2n = 4x = 96) suggested centric fusions behind the 2n reduction. Variable patterns of FISH signals revealed cases of intraspecific polymorphisms, rDNA amplification, variable degree of correspondence with CMA3+ sites and almost no phylogenetic signal. In tetraploids, either additivity or loci gain/loss was recorded. Despite absence of classical interstitial telomeric sites, large blocks of interspersed rDNA/telomeric regions were found in diploids only. We uncovered different molecular drives of studied repetitive DNA classes within botiid genomes as well as the advanced stage of the re-diploidization process in tetraploids. Our results may contribute to link genomic approach with molecular cytogenetic analyses in addressing the origin and mechanism of this polyploidization event.

Induction of triploidy and gynogenesis in teleost fish with emphasis on marine species

The induction of triploidy and gynogenesis by chromosome set manipulation has traditionally been studied more intensively in freshwater than in marine fish. In the last years, however, several studies have applied these manipulations in about a dozen marine species, including mainly sparids, moronids and flatfishes. This paper focuses on the methodologies used to induce, verify, and assess performance of both triploids and gynogenetics of these marine species. Since many of them are batch spawners and have small and fragile eggs and larvae, peculiarities relating to broodstock management, gamete quality and mortality assessment during early larval stages are also taken into account. However, data show that if handling is correct and the treatments are optimized, triploid and gynogenetic rates of 100% can be easily achieved. Survival of triploids with respect to the controls is about 70-80%, whereas in gynogenetics it is generally low and more variable, depending on the species considered. In the marine fish investigated so far, triploidy has not resulted in significantly higher growth rates. On the other hand, the induction of gynogenesis has resulted in the production of both all-female and mix-sex stocks. Throughout the paper, special reference is made to the European sea bass (Dicentrarchus labrax L.), a species of both basic and applied interest, for which a comprehensive study has been carried out on the induction, verification and performance of triploids and gynogenetics.