Donkan Ryoku (Low temperature insensitivity) of rice

Rice is a plant of subtropical origin and cold disorder is a major problem in rice cultivation in Hokkaido. Rice is said to be the lowest temperature weakest in the booting stage, two weeks before flowering. Most studies find and introduce resistance genes from the idea that plants respond positively to various stresses to obtain resistance. We discovered an example different from the conventional way of thinking ‘Donkan Ryoku’ (low temperature insensitivity) which shows stress tolerance by not feeling low temperature stress. In addition, lower temperature disorders are effective not only for improving cold tolerance at the booting stage but also at low temperatures from late summer to autumn due to early birth. Therefore, we investigate the relation between photoperiod and temperature condition and growth rate and try to deepen the understanding of adjustment of heading period. (Y. Kurasawa, K. Yamamori, S. Sakaguchi, S. Kikuchi)

Transposition control of transposon Tam3 in Antirrhinum majus

Transposition of transposons is one of the phenomena creating gene mutation, which is important for plant breeding. In Antirrhinum majus, when the transposon Tam3 transposed from a certain locus, a pigment gene begins to express and the flower colour changes. This transposition is promoted under cold conditions. In our laboratory, we analyze the mechanism by which Tam3 is transposed on the genome. Our final goal is establishing transposons as a new method of plant breeding.

Analysis of regenerated plants and the mechanism of microspore dedifferentiation through anther culture.

Do you know what will happen when culturing rice anthers filled with pollen? Callus (undifferentiated plant cell) appears and grows to regenerated plants. These regenerants have almost similar traits like normal parent plants, but due to somaclonal variations, some of the regenerated plants show some specific characteristics, including albinism and higher ploidy levels. That is why these regenerants are useful as research targets to investigate the plant’s mechanism of reproduction and growing process. Through “anther culture” approach, our team has got successes to produce high ploidy (tetraploids) rice lines and regenerants from sterile F1 hybrids between Asian and African cultivated rice. We have also made efforts to observe meiotic abnormalities of high ploidy rice and uncover the mechanism of callus induction and genotype differences in albinism frequencies.

Understanding and Breaking “Reproductive Barriers” in Rice

The species barrier, known as the reproductive barrier, acts to prevent the exchange of genes between species. The barrier also prevents the creation of new crops through interspecific crossing in breeding.
We use hybrid sterility in rice as a model case of the barrier to understand its molecular mechanisms, its evolution, and the way to overcome it. Focusing on the hybrid sterility observed in Asian and African cultivated rice species, we aim to identify the causal genes and create a new allele ,which can avoid the sterility through mutagenesis and genome editing.

Gene analysis using rice mutant

Mutants are important materials for genetic and breeding research, therefore we induce and select various mutants. In mutants, genes are altered, resulting in loss of gene function or diminished function. By examining these mutants, we will be able to recognize and investigate the gene for the first time.

Rice leaves and spikelets are important traits related to rice yield. Many genes act on these formations. Examining the function of these genes is an important research subject as the basis of breeding, and we are conducting research using various mutants related to rice morphology.

A) A zebra mutant showing leaves with horizontal stripes of chlorosis during the seedling stage in rice. (B) Various malformed spikelets in the progeny of crossing between mutants that cause malformations in the spikelet structure in rice. (C) Testing of mutants with variations in seed size. (D) Cultivation and selection of mutants in paddy fields.

Exploring the Nature of Form and Motion of Plants by Using Computational Models

How are the complex shapes and movements of plants controlled? We use mathematical modeling to reproduce the shape and movement of plants by computer to explore their essential mechanisms. We are also developing a measurement method to understand the shape and movement of plants.
Moreover, we use models to understand phenomena that are impossible to reproduce, such as the evolution of plants.
A variety of crops, such as rice and soybean, are used depending on the individual study. We aim to create new crops based on our understanding of shape and movement mechanisms.

Rice production in Hokkaido

Hokkaido is a major producer of rice, boasting Japan’s largest crop acreage and yield. Most rice grown in Japan is from the Japonica variety, which has a rounder pill-like shape and stickier texture compared to the Indica or Javanica varieties.

Rice cultivation in Hokkaido has developed over the years by overcoming the harsh climate that includes cold temperatures and heavy snowfall. Since the variety called Kirara 397 debuted in 1989, breeding has been used to develop other types of Hokkaido rice that taste better and withstand the cold climate better. The Nanatsuboshi and Yumepirika varieties are highly acclaimed for their glossy appearance, sticky texture and great balance of sweetness. Both have received the Toku-A ranking, the highest possible, in taste tests performed by the Japan Grain Inspection Association. Currently, Hokkaido is cultivating rice in a more safe and secure manner by taking advantage of its colder climate to use less agricultural chemicals.

Northern extensions of rice cultivation limit
Summer average temperature lines in Hokkaido (left)
Years of progress for rice varieties to north area in Hokkaido (Right)


  • Meilan Xu
    Research Title:The mechanism of microspore dedifferentiation in rice anther culture

Research Student

    Research Title:Molecular genetic studies on hybrid sterility between O.sativa and O.glaberrima 
  • Thet Htar san
    Research Title:Integrated Molecular Breeding Studies on Rice of Myanmar
  • Md. Imdadul Hoque
    Research Title:Identification of the gene for thermosensitivity associated with heading in Hokkaido rice varieties


  • Elias George Balimponya
    Research Title:Determining the cause of albino in rice breeder’s seeds and elucidating natural mutation incidence using Whole Genome Sequencing


  • Wang Shasha
    Research Title:Functional analyses of the Stabiliser genes that suppress transposon Tam3 activities of Antirrhinum majus
  • Zin Mar Myint
  • TOKUYAMA Yoshiki
    Research Title:Computational modeling of morphodynamics in rice


  • ISHIHARA Megumi
    Research Title:Cytogenetical analyses of meiosis abnormality in Asia-Afirica interspecific rice and autotetraploid rice
  • KOHTOKU Yuta
    Research Title:Adaptive evolution of fossil virus segments endogenous to the rice genome toward acquisition of innate immunity mechanism
  • TAKATORI Masaki
    Research Title:Genetic association with flowering and cold tolerance in Hokkaido rice varieties
  • HIKICHI Kiwamu
    Research Title:Build New Phenotyping Methods with 3D Data / Computational Modeling of the Mechanism of Soybean Seed Formation / Genetic and phenotypic analysis of rice twisted leaf mutants
    Research Title:Elucidation of the genetic mechanism associated with seed fertility in the interspecific hybrids of Asia-African rice.
  • Zhou Shuaiyu
    Research Title:The phylogenetic analysis of Tam3 transposase responsible for low-temperature dependent transposition in Antirrhinum


  • ITOH Takeshi
    Research Title:Genomic dynamisms of microspores during rice anther culture
  • Omachi Miku
    Research Title:Computational modeling of genetic factors controlling the shape of wild rice plants.
  • AOKI Sae
    Research Title:Molecular genetic analysis of the femele gametes abortion in interspecific rice hybrids.
  • IGUCHI Kokoro
    Research Title:Genetic basis of the interspecific hybrid vigor in rice
  • TANABE Ryuya
    Research Title:Elucidation of the mechanism of Old Stabiliser gene which suppresses activity of transposon Tam3 in Antirrhinum 
  • KUDO Nanami
    Research Title:Identifications of the causative genes associated with the traits on rice anther culture efficiency
  • HIRANO Shoya
    Research Title:Genetics and breeding studies on phenotipic characteristics of tetraploid rice varieties and endsperm development
  • Kayyis Muayadah Lubba
    Research Title:Functional analyses of the rice genes affected by cold-stress 
  • Shuhei Okada
    Research Title:QTL analysis of agronomic traits in tetraploid rice
  • Wakana Takanishi
    Research Title:Molecular genetic study on the pollen killer gene in interspecific rice hybrids

BC 4

  • Saigusa Masaya
    Research Title:Development of two-component system for Tam3 transposition in Arabidopsis lines
  • SATO Ayu
    Research Title:Cytogenetic analyses of meiotic anomaly with male gamete in the tetraploid rice varieties
  • KUSHIDA Shiori
    Research Title:Three-dimensional analysis of culm kinematics in wild rice 
  • MIURA Seiichiro
    Research Title:Toward understanding of the morphogenesis process of palea and lemma in rice
  • KAMACHI Ikumi
    Research Title:Development of polyploid rice using genome editing technologies