Genome sequence of the plant growth-promoting rhizobacterium Bacillus sp. strain JS.

Volatile and nonvolatile compounds emitted from the plant growth-promoting rhizobacterium Bacillus sp. strain JS enhance the growth of tobacco and lettuce. Here, we report the high-quality genome sequence of this bacterium. Its 4.1-Mb genome reveals a number of genes whose products are possibly involved in promotion of plant growth or antibiosis.

Cadmium resistance in tobacco plants expressing the MuSI gene.

MuSI, a gene that corresponds to a domain that contains the rubber elongation factor (REF), is highly homologous to many stress-related proteins in plants. Since MuSI is up-regulated in the roots of plants treated with cadmium or copper, the involvement of MuSI in cadmium tolerance was investigated in this study. Escherichia coli cells overexpressing MuSI were more resistant to Cd than wild-type cells transfected with vector alone. MuSI transgenic plants were also more resistant to Cd. MuSI transgenic tobacco plants absorbed less Cd than wild-type plants. Cd translocation from roots to shoots was reduced in the transgenic plants, thereby avoiding Cd toxicity. The number of short trichomes in the leaves of wild-type tobacco plants was increased by Cd treatment, while this was unchanged in MuSI transgenic tobacco. These results suggest that MuSI transgenic tobacco plants have enhanced tolerance to Cd via reduced Cd uptake and/or increased Cd immobilization in the roots, resulting in less Cd translocation to the shoots.

Alteration of floral organ identity by over-expression of IbMADS3-1 in tobacco.

The MADS-box genes have been studied mainly in flower development by researching flower homeotic mutants. Most of the MADS-box genes isolated from plants are expressed exclusively in floral tissues, and some of their transcripts have been found in various vegetative tissues. The genes in the STMADS subfamily are important in the development of whole plants including roots, stems, leaves, and the plant vascular system. IbMADS3-1, which is in the STMADS subfamily, and which has been cloned in Ipomoea batatas (L.) Lam., is expressed in all vegetative tissues of the plant, particularly in white fibrous roots. Sequence similarity, besides the spatial and temporal expression patterns, enabled the definition of a novel MADS-box subfamily comprising STMADS16 and the other MADS-box genes in STMADS subfamily expressed specifically in vegetative tissues. Expression of IbMADS3-1 was manifest by the appearance of chlorophyll-containing petals and production of characteristic changes in organ identity carpel structure alterations and sepaloidy of the petals. In reverse transcription-polymerase chain reaction analysis with a number of genes known to be key regulators of floral organ development, the flowering promoter NFL1 was clearly reduced at the RNA level compared with wild type in transgenic line backgrounds. Moreover, NtMADS5 showed slight down-regulation compared with wild-type plants in transgenic lines. These results suggest that IbMADS3-1 could be a repressor of NFL1 located upstream of NtMADS5. IbMADS3-1 ectopic expression is suggested as a possible means during vegetative development by which the IbMADS3-1 gene may interfere with the floral developmental pathway.