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)

Research Student

  • Chengfang Zhan
    Research Title:
    Selection of cold sensitive/resistance grain filling trait in F2 populations


  • KANAOKA Yoshitaka
    Research Title:Integrated study of genetic control mechanisms related to plant regeneration from rice microspores
  • KUNIYOSHI Daichi
    Research Title:Analysis of abnormal meiosis and gamete polyploidization in F1 hybrid between two rice cultivars Oryza sativa and O. glaberrima.


  • YAMAMORI Koichi
    Research Disruption mechanism of low temperature stress for gametogenesis in rice


  • Elias George Balimponya
    Research Title:Screening of doubled haploid rice lines adapting in East Africa and probing genetic causes of albino plants in anther culture procedures


  • INADA Satoshi
    Research Title:Genetic analysis of the mutant showing zebra chlorosis and tillering dwarf in rice
  • KITAJIMA Katsuya
    Research Title:Genetic analysis of common genome regions of diploid regenerated plants derived from F1 between Asian and African rice
  • MITSUI Shigetomo
    Research Title:Elucidation of causative substances causing low temperature dependent transposition of transposon Tam3 in Antirrhinum
  • Joseph Enoch Garcon
    Research Title:Rice spikelet mutants for morphogenesis and size
  • Wang Shasha
    Research Title:Functional analyses of the Stabiliser genes that suppress transposon Tam3 activities of Antirrhinum majus
  • Zin Mar Myint


  • KOHNO Kenta
    Research Title:Genetic interactions about heading date and temperature in rice varieties from Hokkaido
  • SAITOH Ryosuke
    Research Title:Breeding genetic study about Noted-berry-like endosperm traits caused by low temperatures during the maturation period in Hokkaido rice lines.
  • TOKUYAMA Yoshiki
    Research Title:Computational modeling of morphodynamics in rice
  • NAGAI Mamiko
    Research Title:Genetic Analysis of Spikelet Mutants for Morphogenesis in Rice Focused on Sterile Lemmas and Rudimentary Glumes
  • HOSHI Sakura
    Research Title:Analysis of dedifferentiation mechanism of rice microspores focusing on epigenetic modifications
    Research Title:Molecular evolutionary analysis of hybrid sterility genes using African wild and cultivated rice and analysis of hybrid sterility effects on ploidy individuals

BC 4

  • ISHIHARA Megumi
    Research Title:Comparison analysis of meiosis between high fertility rice and low fertility rice
  • ITOH Takeshi
    Research Title:Genetic analysis of zebra mutant with tillering dwarf in rice
  • KOHTOKU Yuta
    Research Title:Analysis for molecular mechanism of Old stabiliser suppressing transposition of Antirrhinum majus transposon Tam3
  • TAKATORI Masaki
    Research Title:Genetic interactions about heading date and cold tolerance in rice varieties from Hokkaido
  • HIKICHI Kiwamu
    Research Title:Build New Phenotyping Methods with 3D Data / Computational Modeling of the Mechanism of Soybean Seed Formation

BC 3

  • 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:Genetic breeding analysis of low temperature stress sensitive lines caused by transgressive segregation between Hokkaido rice strains
  • KUDO Nanami
    Research Title:Microspore development stages affect plastid differentiation which alters Albino frequency in rice(Oryza sativa) anther culture
  • HIRANO Shoya