Abstract: The morphology, toxicity and partial sequences of beta and alpha subunits including the intergenic spacer (cpcBA-IGS) of the phycocyanin operon were studied in 21 strains of nonaxenic cyanobacterial cultures. The cultures were established from water samples collected in the Thuathien Hue province in Vietnam, 2004. Based on testing for the presence of the mcyA gene, microcystin-production of Microcystis aeruginosa, M. botrys and M. panniformis was confirmed. The presence of the mcyA gene in a strain of Microcystis flos-aquae and a strain of Planktothrix spiroides (HA308) revealed their toxic potential. The phylogeny of the Vietnamese cyanobacteria was inferred using sequences encoding the cpcBA genes. There was no correlation between toxic characters based on ELISA, HPLC and mcyA gene and the phylogeny based on partial cpcBA sequences. Although the resulting tree topology assisted in resolving the phylogeny of some strains of Anabaena, Dolichospermum and Planktothrix, taxonomical problems still exist at the species level for Lyngbya and Microcystis. Future morphological and molecular studies will have to solve these issues.

Abstract: The diploid sporophytes of brown seaweed, Saccharina japonica (Aresch.) C.E. Lane, C. Mayes, Druehl et G.W. Saunders, produce spores after meiosis, which develop into haploid female and male gametophytes with a sex ratio of 1:1. This ratio, as well as the results that all gametophytes produced by zoospores generated by parthenogenetic sporophytes are females, suggest that an X/Y-like sex-determination system exists in S. japonica. To understand the molecular differences between female and male gametophytes, a suppression subtractive cDNA library was constructed. It was found that lhcf6 was one of the differentially expressed genes, and that this differential transcription between the kelp female gametophytes and male ones might result from different promoters. Although no sex-specific genes were screened, several sex-related molecular markers were developed. Based on the high quality chromosomes prepared by pretreatment with multi-enzymes, two molecular markers in relation to the female gametophytes were co-localized on the sporophyte chromosomes, indicating they are female chromosome-specific cytogenetic DNA markers. Whether S. japonica possesses a sex chromosome might be resolved by pairing the kelp sporophyte chromosomes with the help of localized repetitive sequences such as telomere and centromere using fluorescence in situ hybridization techniques.

Abstract: Cell division and reproduction of a cultivated strain of Macrochloris radiosa (Stephanosphaerinia clade) were studied by light- and transmission electron microscopy. Multinucleate cells were frequently observed allowing description of the cell structure and details of the reproduction process. Nuclear staining revealed the position of the multiple polymorphic nuclei between the chloroplast lobes. Ultrastructure of coenocytic cells showed no signs of cleavage of the protoplast in the cytoplasm, although basal bodies were already present within the multinucleate cells. In the further course of the reproduction, biflagellate zoospores were developed that retained their flagella during sporulation. Zoospores were subsequently released from the sporangia.

Abstract: Saccharina japonica is an economically important alga worldwide as a source of of alginate, mannitol and iodine etc. China contributes 60 % of S. japonica production volume and 90 % of its alginate globally. Like the land crops, S. japonica is also plagued by diseases initi- ated by causative bacteria, fungi or viruses. In this article, we review investigations over the last 50 years on microbial diseases in nursery and fi eld-cultivated S. japonica in China, including the etilology of two different sources of diseases occurring in S. japonica cultivation, the prev- alence of causative alginic acid-decomposing bacteria and the recent progress in the under- standing of innate immunity mechanisms of S. japonica. Meanwhile, we highlight the questions for future research and advocate that researchers from different disciplines apply traditional technologies and newly emerging ones to elucidate the S. japonica microbial diseases. The full understanding of interactions between S. japonica, causative bacteria and environmental fac- tors will help to develop management strategies for preventing and mitigating the disease out- breaks in S. japonica aquaculture in the long term.