The chloroplast GATA-motif of Mahonia bealei participates in alkaloid-mediated photosystem inhibition during dark to light transition.

Mahonia bealei and Mahonia fortunei are important plant resources in Traditional Chinese Medicine that are valued for their high levels of benzylisoquinoline alkaloids (BIAs). Although the phytotoxic activity of BIAs has been recognized, information is limited on the mechanism of action by which these compounds regulate photosynthetic activity. Here, we performed comparative chloroplast genome analysis to examine insertions and deletions in the two species. We found a GATA-motif located in the promoter region of the ndhF gene of only M. bealei. K-mer frequency-based diversity analysis illustrated the close correlation between the GATA-motif and leaf phenotype. We found that the GATA-motif significantly inhibits GUS gene expression in tobacco during the dark-light transition (DLT). The expression of ndhF was downregulated in M. bealei and upregulated in M. fortunei during the DLT. NDH-F activity was remarkably decreased and exhibited a significant negative correlation with BIA levels in M. bealei during the DLT. Furthermore, the NADPH produced through photosynthetic metabolism was found to decrease in M. bealei during the DLT. Taken together, our results indicate that this GATA-motif might act as the functional site by which BIAs inhibit photosynthetic metabolism through downregulating ndhF expression during the DLT.

Molecular characterization and functional analysis of the GATA4 in tongue sole (Cynoglossus semilaevis).

The GATA family of transcription factors is characterized by two zinc finger domains and is involved in different cellular processes. GATA4 is a highly conserved transcription factor that regulates embryonic morphogenesis and cellular differentiation. GATA4 in vertebrates regulates its target genes to influence genital ridge differentiation. In this study, the GATA4 from tongue sole (Cynoglossus semilaevis) was characterized to understand the function of this transcription factor in sex differentiation. The full-length cDNA of C. semilaevis GATA4 comprised 2031bp, encoding a predicted polypeptide consisting of 402 amino acids with two conserved zinc finger domains. Phylogenetic, gene structure, and synteny analyses showed that C. semilaevis GATA4 was homologous to tetrapod GATA4. The mRNA transcript of C. semilaevis GATA4 exhibited high expression in the heart, liver, and gonad. GATA4 expression is dimorphic in the male and female gonads. Embryonic development expression profiles revealed the possible involvement of C. semilaevis GATA4 in morphogenesis. In situ hybridization results showed strong GATA4 signals in the spermatogonia and spermatocytes of the testis and in the oogonia, primary oocytes, and secondary oocytes of the ovary. The expression of C. semilaevis GATA4 in the male, pseudomale, and female gonads showed significantly different methylation levels of the two CpG sites (-2738 and -2647) among the three genders. Basing on these results, we speculated that GATA4 plays a potential role in sex differentiation. This study lays the groundwork for further sex control breeding techniques in C. semilaevis.

Identification and Characterization of a PRDM14 Homolog in Japanese Flounder (Paralichthys olivaceus).

PRDM14 is a PR (PRDI-BF1-RIZ1 homologous) domain protein with six zinc fingers and essential roles in genome-wide epigenetic reprogramming. This protein is required for the establishment of germ cells and the maintenance of the embryonic stem cell ground state. In this study, we cloned the full-length cDNA and genomic DNA of the Paralichthys olivaceus prdm14 (Po-prdm14) gene and isolated the 5' regulatory region of Po-prdm14 by whole-genome sequencing. Peptide sequence alignment, gene structure analysis, and phylogenetic analysis revealed that Po-PRDM14 was homologous to mammalian PRDM14. Results of real-time quantitative polymerase chain reaction amplification (RT-qPCR) and in situ hybridization (ISH) in embryos demonstrated that Po-prdm14 was highly expressed between the morula and late gastrula stages, with its expression peaking in the early gastrula stage. Relatively low expression of Po-prdm14 was observed in the other developmental stages. ISH of gonadal tissues revealed that the transcripts were located in the nucleus of the oocytes in the ovaries but only in the spermatogonia and not the spermatocytes in the testes. We also presume that the Po-prdm14 transcription factor binding sites and their conserved binding region among vertebrates. The combined results suggest that Po-PRDM14 has a conserved function in teleosts and mammals.

Characterization of the Dmrt1 gene in the black rockfish Sebastes schlegeli revealed a remarkable sex-dimorphic expression.

The Dmrt genes encode a large family of transcription factors with a conserved zinc finger-like DNA-binding DM domain. The function of Dmrt1, one of the family members, in sexual development has been well studied in invertebrates and vertebrates. In the present study, the full-length cDNA of Dmrt1 was isolated from the testis of Sebastes schlegeli. The full-length cDNA of S. schlegeli Dmrt1 (SsDmrt1) was 1,587 bp and contained a 189-bp 5' UTR, a 489-bp 3' UTR and a 909-bp open reading frame, which encoded 302 amino acids with a conserved DM domain and an male-specific motif domain. Phylogenetic analysis showed the evolutionary relationships of SsDmrt1 with other known Dmrt genes in fish and tetrapods. Several transcriptional factor-binding sites in the 5' promoter were identified that might regulate SsDmrt1 expression. Quantitative real-time PCR analysis indicated that SsDmrt1 was expressed in all of the inspected larval developmental stages from 1 to 35 days after birth and that the level of expression gradually decreased. The expression of SsDmrt1 in adult gonads was sexually dimorphic with extremely high expression in the testis, but very low expression in the ovary. No expression was detected in other tissues. Using in situ hybridization, we demonstrated that SsDmrt1 was specifically expressed in the germ cells of both the testis and the ovary. Thus, our results suggest that SsDmrt1 may have an important role in the differentiation of both the testis and the ovary of S. schlegeli.