Yuichi Tada

Title : Roles of Potassium transporters in salt tolerance of plants

Abstract:

1. Halophytic wild turf grasses

Salinity stress is one of the most significant limiting factors in agricultural crop productivity. Hence, improving the salt tolerance of crops is essential for sustainable food production. Halophytes are widely spread over higher plant families and orders and exhibit a broad variety of adaptations to salt. Wild turf grasses are known to be relatively resistant to salt. We examined the salt tolerance of more than 30 species of wild turf grasses collected from all over Japan and showed that Sporobolus virginicus is the most salt tolerant among them, which tolerate up to 1.5 M NaCl (Tada et al. 2014).

1. Ion managements in plants under salt stress

Plants have been classified into two categories, salt includers and salt excluders, from how to deal with sodium ion. Salt includers take up sodium ion and translocate it to the shoot, where it is sequestered and used as vacuolar osmoticum to decrease the water potential, whereas salt excluders adapt to saline environments by avoiding sodium ion accumulation. Ion channels including potassium transporters play important roles in the ion management. In Arabidopsis, a salt excluder, AtHKT1;1 contributes to the retrieval of sodium ion from the xylem to repress accumulation of sodium ions in shoots. I found that most of wild turf grasses are salt includers and that they have diverse ion accumulation patterns.

1. Functions of potassium transporters from a salt tolerant turf grass

We have cloned genes for potassium transporters from S. virginicus and have been characterizing their functions in potassium/sodium transport. SvHKT2;1 and SvHKT2;2 mediate distinct outward and inward K⁺ and Na⁺ transport activity in plants (Tada et al. 2019). Constitutive expression of the SvHKT2s in transgenic Arabidopsis resulted in reduced salt tolerance but their specific expression in xylem parenchyma cell enhanced the plant growth under mild salinity. SvHKT1;1 mediate inward Na⁺ transport activity and is possibly the counterpart of AtHKT1;1. I will discuss the roles of these transporters in salt tolerance in relation to their tissue/organ specificity.

1. Acquisition of potassium and sodium by potassium transporters

I would like to discuss the possibility of modifying the availability of potassium and sodium as fertilizer in transgenic plants expressing SvHKTs.

Biography:

Dr. Tada studied Agriculture Science at the Tokyo University, Japan and graduated as MS in plant breeding science in 1988. He joined the research group of Plant Biotechnology at Mitsui Toatsu Chemicals, Inc., Japan in 1988 and worked on rice molecular breeding and rice conventional breeding. He received his PhD in Agriculture in 1992 at the Tokyo University. While he was working for Mitsui Toatsu Chemicals, Inc., he turned to Mitsui Plant Biotechnology Research Institute from 1996 to 1999. He moved to School of Bioscience and Biotechnology, Tokyo University of Technology, Japan in 2005. He has been working on Plant molecular breeding in stress tolerance and phytoremediation. He has published more than 40 research articles.