Research interests

Plants are continually exposed to a variety of microbes. Some microbes can establish symbiotic relationship with plants and support their them. To achieve sustainable agriculture, it is important to utilize those beneficial microbes and reduce agricultural chemicals. The work in our laboratory covers (1) Isolation and characterization of symbiotic microbes from various plants around the world, (2) Molecular dissection of plant-microbe interactions, and (3) Application of beneficial microorganisms for agricultural production. We are currently conducting following research.

Legume-Rhizobium symbiosis

Leguminous plants such as soybean and pea establish symbiosis with a group of soil bacteria called rhizobia. Rhizobia induce the development of root nodules in leguminous plants and fix atmospheric dinitrogen to ammonia, which can be effectively used by the host plants.

Root-nodule symbiosis between leguminous plants and rhizobia requires rhizobial Nod factors (NFs) and their leguminous receptors (NFRs). Recently we revealed that symbiosis in the soybean rhizobium Bradyrhizobium elkanii is promoted by the type III secretion system (T3SS), which delivers virulence factors via　pathogenic bacteria. Nodulation tests and expression analyses using mutants of both B. elkanii and soybean (Glycine max) revealed that rhizobial T3SS activates host nodulation signaling in the absence of NFs and NFRs. These results suggest that rhizobia have adopted a pathogenic system that stimulates their legume hosts to initiate symbiotic programs[Okazaki et al. (2013) PNAS.; Okazaki et al. (2016)The ISME J.]

Leguminous plants belong to the genous Vigna contain improtant crops such as mung bean and cowpea. We isolated several mutants of rhizobia that have improved nodulation and nitrogen-fixation ability. The genes responsible for the improved symbiotic performance of rhizobia are now being cloned and characterized.[Nguyen et al. (2017) Genes.; Nguyen et al. (2018) Frontiers Microbiol.]

Endophytes（Microbes living inside plants）

Endophytes are microbes (fungi and bacteria) that live inside plants. Unlike pathogenic microbes, endophytes do not cause a negative impact on host plants, rather confer a beneficial effects such as nutrient acquision and stress torelance to biotic and abiotic stresses.

Azospirillum sp. B510 is an endophytic bacteria that colonize in rice. Colonization of B510 and beneficial effects are influenced by soil nutrient condition, suggesing that host plants control the symbiosis with endophytes depend on plant nutrient status [Naher et al. (2018) Microbes and Environ.]

Arbuscular mycorrhizal fungi

Arbuscular Mycorrhizal Fungi (AMF) can establish symbiosis with about 80% of plants. They provide the host with water, nutrients (especially phosphate), and pathogen protection, in exchange for photosynthetic products.

In Ghana, demand for rice is increasing rapidly much higher than its domestic production. We work together with Ghananian collaborators toward the understanding of the genetic diversity of AMF associated with rice and its application for sustainalbe rice production in Ghana.