Molecular Genetics and Physiology
|Activities in Academic Societies||
American Society of Plant Biologists, American Society for Photobiology, The Japan Radiation Research Society, Japan Society of Plant Physiologists, Japanese Society for Biological Sciences in Space
Genome Inheretance Systems, Joint Lecture on Ecology, Introduction to Life Science, Life Science B
Deterioration of the global environment is a growing concern. I am particularly interested in the increased levels of hazardous ultraviolet-B (UVB; 280–320 nm) radiation attributed to the depletion of the stratospheric ozone layer, and I have been investigating the following two areas with the aim of sustainable food production and global environment conservation in the near future: 1) the mechanism of resistance to UVB radiation in higher plants and the creation of new cultivars resistant to UVB radiation, and 2) field testing the impact of solar ultraviolet (UV) radiation on rice.
I have also been applying multidisciplinary approaches that employ concepts and methods of plant physiology, molecular cell biology, molecular genetics, photobiology, and radiation biology to gain comprehensive insights into the impact of UVB radiation on plants at the molecular, cellular, individual, and population levels.
The mechanism of resistance to UVB radiation in higher plants and the creation of new cultivars resistant to UVB radiation
UVB can damage plants, resulting in decreased growth and productivity. Consequently, plants with decreased resistance to UVB damage may become severely damaged when UVB radiation is high, such when stratospheric ozone is depleted. We previously demonstrated that UVB-induced cyclobutane pyrimidine dimers (CPDs) are one principal cause of UVB-induced growth inhibition in plants grown under supplementary UVB radiation, and that increasing the activity of CPD photolyase, which is a CPD repair enzyme, can significantly alleviate UVB-caused growth inhibition in rice (Hidema et al. 2000; Plant Cell, 2005; Plant J, 2007). The CPD photolyase is widely distributed among species ranging from bacteria to plants and mammals, indicating that CPD photolyase is an ancient protein that may have played an important role in evolution. We demonstrated that rice CPD photolyase, encoded by a single-copy gene and not a splice variant, is expressed and targeted not only to nuclei and mitochondria but also to chloroplasts, and is subjected to “triple targeting” in rice cells (M. Takahashi et al. 2011, Plant J.; S. Takahashi et al. 2014, Plant J.). Furthermore, although it has been reported that CPD photolyase gene expression is mediated by various qualities of light (UVB, UVA, blue, or red) in plants, the mechanisms of this light-mediated gene expression is poorly understood. Currently, I am conducting research relating to CPD photolyase and UVB-induced growth inhibition in higher plants, focusing on the organelle transfer mechanism, the light-regulated gene expression mechanism, and structural modification of CPD photolyase.
Field testing the impact of solar ultraviolet (UV) radiation on rice
In environmental research, it is crucial to confirm laboratory findings in field studies. Field studies are also important as they highlight problems in the environment. I have been analyzing the prospective effects of elevated UVB radiation levels on several populations of rice, a staple crop in Asia, for over 10 years, and I have demonstrated that elevated UVB radiation levels in the near future will cause a reduction in grain yield and size, as well as influence the content of major proteins in rice grains (Hidema et al. 2005, J. Radiation Res.). I am also currently involved in a project begun in 2010 (a certified experiment with type-1 genetically modified organisms) that investigates the impact of current solar UVB radiation on the growth and yield of rice in an isolated field using cultivars with distinct levels of resistance to UVB radiation.