Ryohei Terauchi - Plant Genetics - terauchi@ (Please add "ige.tohoku.ac.jp") Adjunct Professor United Graduate School of Agricultural Sciences Project Leader Iwate Biotechnology Research Center Strategic mechanism of biological systems for thermal energy - Genetic analysis of plant adaptation to cold environment -

I. Research achievements
1. Phylogeny and origin of cultivated crops in the genus Dioscorea
My research group studied the phylogeny and origin of cultivated crops in the genus Dioscorea (i.e., "yam"), one of the major crops for the root-tuber farming culture. We analyzed chloroplast DNA to reveal that Dioscorea bulbifera has been domesticated independently in Asia and Africa before becoming a crop widely distributed in the tropical and subtropical zones throughout the world. Guinean Yams, a group of yam species grown in West Africa, is the world's most produced yam group. Among them, our data suggested that Dioscorea rotundata is likely to have been domesticated directly from a wild species in the savanna region (D. abyssinica), while D. cayenensis seems to be originated from a hybrid between a wild species in the tropical rainforest region and one in the savannah region.

2. Phylogenic analysis of monocotyledonous plants
We analyzed the phylogenic relationship among monocotyledonous plants through analysis of rbcL sequence encoded in chloroplast DNA.

3. Molecular population genetics of phosphoglucose isomerase in Dioscorea tokoro
Dioscorea tokoro is a dioecious wild species, which grows widely in East Asia. An allozyme analysis of populations in the Kinki region of Japan revealed polymorphism of phosphoglucose isomerase (PGI), a glycolytic enzyme. Among the three alleles of D. tokoro-Pgi-a, Pgi-b, and Pgi-c-the frequency of Pgi-a was high in the northern part of the Kinki region, while Pgi-c was seen more commonly in the southern part. When the nucleotide sequence at this locus was analyzed, it was found that a) Pgi-b is the ancestral allele, b) Pgi-a and Pgi-c were differentiated independently from Pgi-b by a single amino-acid substitution, c) DNA variation was low at the Pgi locus, and d) the nonsynonymous variation/synonymous variation was significantly higher intraspecifically than interspecifically. These results suggest that natural selection imposed by the environmental conditions (probably temperatures) contributes to the maintenance of the allozyme polymorphism.

4. Linkage analysis of sex-determining factor in Dioscorea tokoro
We developed a linkage map of a dioecious plant, Dioscorea tokoro, by using AFLP and microsatellite marker, and identified an AFLP marker that has a strong linkage to sex-determining factor. The sex-determining mechanism of D. tokoro was found to be the pattern of male-XY: female-XX.

5. Analysis of the molecular mechanism of disease resistance in plants
We have been analyzing the molecular mechanism of disease resistance in plants using rice and Nicotiana species.

6. Analysis of the mechanism of cell death in plants
We have been studying the mechanism of cell death in plants using rice and Nicotiana species.

7. Use of DNA markers in rice
We have been developing DNA markers with an aim to accelerate the procedure of rice crossbreeding.

II. Goals in the COE Program
During many years of breeding efforts, many lines of rice have been developed, and this tropic-originated crop species now can be grown even in the northern part of the temperate zones. This should be a result of practices to select rice lines with genes that contribute to low-temperature adaptation. The understanding of these genes should enable the development of rice with an even higher cold tolerance. Analyses of rice genome have shown that a rice genome contains 30,000 to 50,000 genes. The aim of the research for this project is to identify genes associated with low-temperature adaptation from these and to analyze their functions. In order to achieve these goals, we will use rice to a) develop many DNA markers, b) identify markers associated with chilling tolerance, c) examine mutants, and d) analyze gene expression.

III. Related websites
Iwate Biotechnology Research Center: http://www.ibrc.or.jp
Iwate Agricultural Research Center: http://www.pref.iwate.jp/~hp2088/

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