Enhanced soybean infection by the legume "super-virulent" Agrobacterium tumefaciens strain KAT23.

Agrobacterium tumefaciens KAT23 harbors a nopaline-type Ti plasmid and is "super-virulent" to soybean (Glycine max) and other leguminous plants. The right and left border sequences of the essential cis-element for T-DNA transfer were removed in order to utilize the high infectivity of this strain in an Agrobacterium-mediated soybean transformation system. The resulting strain, named Soy2, showed no oncogenic activity. After inoculation with disarmed Soy2 harboring binary vector pIG121-Hm and pCAMBIA-WR, soybean epicotyls exhibited high beta-glucuronidase activities, with efficiencies higher than EHA105, an A. tumefaciens strain widely used in making transgenic plants.

Characterization and host range determination of soybean super virulent Agrobacterium tumefaciens KAT23.

Agrobacterium tumefaciens KAT23 isolated from peach root causes crown gall disease in a number of grain legume plants, including the common bean (Phaseolus vulgaris) and soybean (Glycine max). KAT23 caused tumor formation in each of these plants more effectively than strain C58. Biotype determination suggested that this strain is biotype II. KAT23 was able to utilize nopaline as a carbon source. Partial sequence analysis indicated that KAT23 harbors a nopaline-type Ti plasmid, designated pTiKAT23, which was highly homologous with other nopaline-type Ti plasmids (pTiC58 and pTiSAKURA). KAT23 transferred not only the T-DNA of the Ti plasmid but also introduced T-DNA of the binary vector efficiently. The common bean inoculated with KAT23 (pIGFP121-Hm) showed crown galls, and some plants showed beta-glucuronidase (GUS) and sGFP (S65T) gene expression. This virulent ability of KAT23 indicates its potential application to legumes, especially to soybean transformation.

Changes of DNaseI Sensitivity of the Fibroin and Sericin Genes during the Silkworm Development: (DNaseI sensitivity/gene expression/silk gland/chromatin structure).

DNasel sensitivity assay of the fibroin gene and the sericin gene in different tissues along developmental stages have revealed unique patters of regulation. In the posterior silk gland the fibroin gene was more sensitive to DNaseI at the larval feeding stages, when the gene is transcriptionally active, than at the larval molting stages, when the gene is inactive. In the middle silk gland and the ovarian tissue where the fibroin gene is suppressed throughout development, the gene was found to be resistant to DNaseI. On the other hand the sericin gene remained rather DNaseI sensitive in the middle silk gland through larval development, where transcription activity of the gene changes drastically. Disappearance of DNaseI sensitivity of the fibroin gene at the fourth molting stage takes place earlier than the decline of the fibroin gene transcription. However, in the fifth feeding stagereappearance of DNaseI sensitivity occurs synchronously with resumption of the fibroin gene transcription. Thus a constitution of the DNaseI sensitivity may be required, but not sufficient to support an active state of genes.