Case Studies on the Seasonal Changes of Diatom Community in Paddy Fields

As a case study, the seasonal changes of diatom community in flooded water of paddy fields were discussed. The investigations were conducted on Andosols (Field 1) at Field Science Center, Tohoku University, and on Fluvisols (Field 2) at Furukawa Agricultural Experimental Station, located at Miyagi Prefecture, Japan, during the rice-growing season of 2004. The results obtained are as follows: 1) Diatom cell density at Field 1 ranged between 2.1x10^5 and 1.1x10^6 cells L^. There was no large difference during the experimental period in Field 1. Diatom cell density in Field 2 ranged between 4.3x10^5 and 5.3x10^6 cells L^. Diatoms in Field 2 were low in the end of May, and increased gradually thereafter. 2) Nineteen genera were observed in Field 1 and twenty-four genera in Field 2. In general, Nitzschia was predominated genus in the both fields. In Field 1, Melosira became predominated from June to August. In Field 2, Navicula was also predominated in July

Characterization of Bombyx mori Nucleopolyhedrovirus orf68 Gene That Encodes a Novel Structural Protein of Budded Virus

AbstractAll lepidopteran baculovirus genomes sequenced to date encode a homolog of the Bombyx mori nucleopolyhedrovirus (BmNPV) orf68 gene, suggesting that it performs an important role in the virus life cycle. In this article we describe the characterization of BmNPV orf68 gene. Northern and Western analyses demonstrated that orf68 gene was expressed as a late gene and encoded a structural protein of budded virus (BV). Immunohistochemical analysis by confocal microscopy showed that ORF68 protein was localized mainly in the nucleus of infected cells. To examine the function of orf68 gene, we constructed orf68 deletion mutant (BmD68) and characterized it in BmN cells and larvae of B. mori. BV production was delayed in BmD68-infected cells. The larval bioassays also demonstrated that deletion of orf68 did not reduce the infectivity, but mutant virus took 70 h longer to kill the host than wild-type BmNPV. In addition, dot-blot analysis showed viral DNA accumulated more slowly in mutant infected cells. Further examination suggested that BmD68 was less efficient in entry and budding from cells, although it seemed to possess normal attachment ability. These results suggest that ORF68 is a BV-associated protein involved in secondary infection from cell-to-cell