Tetsuo Sasakuma

A novel repetitive sequence of sugar cane, SCEN family, locating on centromeric regions

Tandem repetitive sequences consisting of 140-bp repetitive units were cloned from sugar cane genomic DNA and designated the SCEN family. In situ hybridization revealed that they were located on the centromeric region of almost all of the chromosomes of sugar cane. The 140-bp sequence included three CENP-B box-like sequences. Phylogenetic analysis of the members of the SCEN family revealed that the sequences had 75% homology with each other, on average, and that the sequences could not be further classified into smaller subfamilies. The copy number of the sequence was estimated to be 2.6 × 105 per haploid sugar cane genome and, therefore, 4.6 × 103 or 630 kb per chromosome on average.

Dynamics of Tandem Repetitive Afa-Family Sequences in Triticeae, Wheat-Related Species

Abstract. The Afa-family sequences in wheat-related species, Triticeae, are tandem repetitive sequences of 340 bp. All the analyzed Triticeae species carried the sequences in their genomes, though the copy numbers varied about 100-fold among the species. The nucleotide fragments amplified by PCR were cloned and sequenced, and their behavior in the evolution of Triticeae was analyzed by the neighbor-joining (NJ) method. The sequences in genomes with many copies of this family clustered at independent branches of the phylogenic tree, whereas the sequences in genomes with a few copies did not. This may suggest that Afa-family sequences had amplified several times in the evolution of Triticeae, each using a limited number of different master copies. In addition, the sequences of the A and B genomes of hexaploid common wheat indicated that the Afa-family sequences had not evolved in a concerted manner between the genomes. Furthermore, the sequences of each chromosome of the D genome of this species indicated that the sequences had amplified on all over the D-genome chromosomes in a short period.

Variation and Segregation for Rachis Fragility in Spelt Wheat, Triticum Spelta L.

Spelt wheat, Triticum spelta L., has been proved to be rich-sources of useful genes for tolerance to biotic and abiotic stress, and grain quality. But this crop plant has some undesirable traits including glume tenacity and brittle rachis. Free-threshing and reduced fragility of rachis are very important traits for cultivation. The objectives in the present study were to investigate genetic variation of rachis fragility in a wide range of spelt accessions, to examine its genetic segregation pattern, and to clarify if rachis fragility is associated with dosage of chromosome 5A in aneuploid lines of bread wheat. The results demonstrated that spelt germplasm contains a wide range of rachis toughness, and thus selection of spelt wheat with desirable characteristics combined with an appropriate level of tough rachis would be possible. Spike morphology in the F2 plants was segregated into the three types, square-headed, speltoid, and compactoid. The F2 plants with compactoid spikes had the most brittle rachis, followed by the speltoid and square-headed spike F2 plants. Rachis fragility in bread wheat also had genetic variation and was associated with dosage of chromosome 5A.

Genetic variation of high-molecular-weight glutenin subunit composition in Asian wheat

To clarify the genetic properties of the HMW glutenin subunit composition of Asian endemic wheats, SDS–PAGE analysis was conducted using 1,139 bread wheat accessions that were originally collected in Asia. The samples were divided into six regional groups, Western Asia, Caucasia, Central Asia, Afghanistan, Southern Asia, and Eastern Asia. The genotype Glu-A1c, Glu-B1b, and Glu-D1a encoding subunits null, 7+8, and 2+12 had an overall frequency of 55.2%. Thus, we conclude that it is the typical genotype of the HMW glutenin subunits that characterize Asian endemic wheat. The frequency of the typical Asian genotype was relatively high in the central belt of Asia (Western Asia, Afghanistan, and Eastern Asia) and low in the marginal regions (Caucasia, Central Asia, and Southern Asia). In Southern Asia, the frequency of Glu-B1i, which encodes subunit 17+18, was the highest at the Glu-B1 locus. In Caucasia and Central Asia, the frequency of Glu-D1d, which encodes subunit 5+10 (which is considered to be the most useful for making bread), was high. The level of genetic variation, as estimated using the frequencies of the various alleles, was relatively low in the central belt of Asia and high in the marginal regions. Among the three Glu-1 loci, the highest number of alleles was detected at the Glu-D1 locus. This result was caused by the presence of rare Asian specific alleles at the Glu-D1 locus, in which a newly found allele, Glu-D1bs, encoding subunit 2.1+12 was included.