Akifumi Sugiyama

Highly diverse communities of bacteria inhabiting soybean rhizospheres play pivotal roles in plant growth and crop production; however, little is known about the changes that occur in these communities during growth. We used both culture-dependent physiological profiling and culture independent DNA-based approaches to characterize the bacterial communities of the soybean rhizosphere during growth in the field. The physiological properties of the bacterial communities were analyzed by a community

The rhizosphere is the region close to a plant's roots, where various interactions occur. Recent evidence indicates that plants influence rhizosphere microbial communities by secreting various metabolites and, in turn, the microbes influence the growth and health of the plants. Despite the importance of plant-derived metabolites in the rhizosphere, relatively little is known about their spatiotemporal distribution and dynamics. In addition to being an important crop, soybean (<i>Glycine max</i>)

Legume plants have an ability to fix atmospheric nitrogen into nutrients via symbiosis with soil microbes. As the initial event of the symbiosis, legume plants secrete flavonoids into the rhizosphere to attract rhizobia. Secretion of flavonoids is indispensable for the establishment of symbiotic nitrogen fixation, but almost nothing is known about the membrane transport mechanism of flavonoid secretion from legume root cells. In this study, we performed biochemical analyses to characterize the t

ATP-binding cassette (ABC) proteins constitute a large family in plants with more than 120 members each in Arabidopsis and rice, and have various functions including the transport of auxin and alkaloid, as well as the regulation of stomata movement. In this report, we carried out genome-wide analysis of ABC protein genes in a model legume plant, Lotus japonicus. For analysis of the Lotus genome sequence, we devised a new method 'domain-based clustering analysis', where domain structures like the

Organic farming is frequently touted as being beneficial to soil health by increasing microbial community diversity; however, contradictory results exist in the literature. In this study, we compared several organic and conventional potato farms in Colorado for differences in soil nutrients and microbial communities using 454 pyrosequencing of the 18S ribosomal RNA gene. Organic farms showed a slightly higher diversity and evenness within the microbial community compared with conventional farms.

Plant roots nurture a wide variety of microbes via exudation of metabolites, shaping the rhizosphere's microbial community. Despite the importance of plant specialized metabolites in the assemblage and function of microbial communities in the rhizosphere, little is known of how far the effects of these metabolites extend through the soil. We employed a fluid model to simulate the spatiotemporal distribution of daidzein, an isoflavone secreted from soybean roots, and validated using soybeans grow

Flavonoids, one of the most-described group of plant “specialized metabolites”, consist of more than 10,000 structurally diverse compounds. Most flavonoids accumulate in plant vacuoles as glycosides, with some released by the roots into rhizospheres. These flavonoids are involved in biological communications with rhizobia, arbuscular mycorrhizal fungi, plant growth promoting rhizobacteria, pathogens, nematodes, and other plant species. Both aglycones and glycosides of flavonoids are found in roo

Isoflavones play important roles in plant-microbe interactions in rhizospheres. Soybean roots secrete daidzein and genistein to attract rhizobia. Despite the importance of isoflavones in plant-microbe interactions, little is known about the developmental and nutritional regulation of isoflavone secretion from soybean roots. In this study, soybeans were grown in hydroponic culture, and isoflavone contents in tissues, isoflavone secretion from the roots, and the expression of isoflavone conjugates

Saponins are the group of plant specialized metabolites which are widely distributed in angiosperm plants and have various biological activities. The present study focused on α-tomatine, a major saponin present in tissues of tomato (Solanum lycopersicum) plants. α-Tomatine is responsible for defense against plant pathogens and herbivores, but its biological function in the rhizosphere remains unknown. Secretion of tomatine was higher at the early growth than the green-fruit stage in hydroponical

Isoflavones play important roles in rhizosphere plant-microbe interactions. Daidzein and genistein secreted by soybean roots induce the symbiotic interaction with rhizobia and may modulate rhizosphere interactions with microbes. Yet despite their important roles, little is known about the biosynthesis, secretion and fate of isoflavones in field-grown soybeans. Here, we analyzed isoflavone contents and the expression of isoflavone biosynthesis genes in field-grown soybeans. In roots, isoflavone c

Rhizosphere microbial communities are impacted by resident plant species and have reciprocal effects on their host plants. We collected resident soil from five wild populations of Arabidopsis in the United States and Europe in an effort to characterize the impacts of natural soil microbiomes on Arabidopsis growth performance. The microbial communities present in these soils showed differences in community structure as assessed by 454 sequencing and in metabolic activity. While pathogens associat

Soyasaponins are triterpenoid saponins widely found in legume plants. These compounds have drawn considerable attention because they have various activities beneficial for human health, and their biosynthesis has been actively studied. In our previous study, we found that legume plants including soybean secrete soyasaponins from the roots in hydroponic culture throughout the growth period, but the physiological roles of soyasaponins in the rhizosphere and their fate in soil after exudation have

Legume plants have a unique ability to fix atmospheric nitrogen via symbiosis with rhizobia. For the establishment of symbiosis, legume plants secrete signaling molecules such as flavonoids from root tissues, leading to the attraction of rhizobia and the induction of rhizobial nod genes. Genistein and daidzein are found in soybean root exudates and function as signal molecules in soybean-Bradyrhizobium japonicum chemical communication. Although it is more than 20 years since these signal flavono

Symbiotic nitrogen fixation in legumes contributes greatly to the global nitrogen cycle on the earth. In nodules, resident rhizobia supply nitrogen nutrient fixed from atmospheric N2 to the host plant; in turn, the plant provides photosynthetic metabolites to bacteroids as a carbon source. In this process, various transporters are involved at different membrane systems; however, little is known at the molecular level about the flow of carbon from the host cells to the symbiotic bacteria. We have