Expression analysis of different ß-carotenoid hydroxylase gene families in stress response in Dunaliella viridis.

ß-carotenoid hydroxylase (CHYB) is an important rate-limiting enzyme in the biosynthesis of plant carotenoid. In this study, chyb1 and chyb2, two gene families in Dunaliella viridis were obtained by RNA-seq. The fragment of promoters of CHYB family genes, 1 080 bp for chyb1 (GenBank No. KY012338) and 1 155 bp for chyb2 (GenBank No. KY012339) were cloned by the Genome Walking Technology, respectively. Cis-acting elements of two promoters were analyzed by Plantcare soft. The results show that the chyb1 gene promoter contains more cis-acting elements in responses to abiotic stresses, such as methyl jasmonate, arachidonic acid, acetylsalicylic acid, and so on. On the other hand, the chyb2 promoter contains more cis-acting elements in response to light stress. qRT-PCR results show that the mRNA expression levels of CHYBs are modulated by their promoters, and different CHYB gene families response to distinct stresses.

[Transcriptome analysis of Dunaliella viridis].

In order to understand the gene information, function, haloduric pathway (glycerolipid metabolism) and related key genes for Dunaliella viridis, we used Illumina HiSeqTM 2000 high-throughput sequencing technology to sequence its transcriptome. Trinity soft was used to assemble the data to form transcripts. Based on the Clusters of Orthologous Groups (COG), Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG ) databases, we carried out functional annotation and classification, pathway annotation, and the opening reading fragment (ORF) sequence prediction of transcripts. The key genes in the glycerolipid metabolism were analyzed. The results suggested that 81,593 transcripts were found, and 77,117 ORF sequences were predicted, accounting for 94.50% of all transcripts. COG classification results showed that 16,569 transcripts were assigned to 24 categories. GO classification annotated 76,436 transcripts. The number of transcripts for biologcial processes was 30,678, accounting for 40.14% of all transcripts. KEGG pathway analysis showed that 26,428 transcripts were annotated to 317 pathways, and 131 pathways were related to metabolism, accounting for 41.32% of all annotated pathways. Only one transcript was annotated as coding the key enzyme dihydroxyacetone kinase involved in the glycerolipid pathway. This enzyme could be related to glycerol biosynthesis under salt stress. This study further improved the gene information and laid the foundation of metabolic pathway research for Dunaliella viridis.

[Toxic Effect of Nano-ZnO in Liver of Zebrafish].

For acute toxicity test, zebrafish were respectively exposed to the different concentrations of nano-ZnO (0, 0.05, 0.1, 5, 10, 25, 50 mg x L(-1)) for 4, 24 and 96 h. The superoxide dismutase (SOD), malondialdehyde (MDA), and catalase (CAT) in the liver of zebrafish were studied, and the relative expression of Bcl-2, Bax, p53 and MDM2 in liver were also determined. Anatomical structure of the zebrafish liver was determined after exposure to nano-ZnO for 7, 15 and 30 d. Compared with the control group, the liver of the experimental groups showed obvious difference in following aspects: (1) oedema, cytoplastic vacuolation, and pyknotic nucleus were observed; (2) the number of hepatic macrophages deposited and the sinus clearance were increased; (3) the MDA contents and the activity of SOD were increased; (4) however, the activity of CAT was decreased; (5) the mRNA expression level of genes Bax/Bcl-2 ratio and p53 of stressed groups were up-regulated; the mRNA expression level of gene MDM2 down-regulation can be observed in the low concentration groups while the mRNA expression level of gene MDM2 was up-regulated in the high concentration groups. The results suggested that, the oxidative damage of nano-ZnO to the zebrafish liver was caused by the increase of oxidative stress, which made the change of antioxidant enzyme activity, induced the expression of cell apoptosis genetic and cell apoptosis, and caused the change of organizational structure of liver.