K. Murai¹, R. Murai¹, S. Takumi² and Y. Ogihara³ (¹Res. Inst. Agr. Resour., Ishikawa Agr. Coll. ²Fac. Agr., Kobe Univ., ³Kihara Inst. Biol. Res., Yokohama City Univ.)
Cloning and characterization of cDNAs corresponding to the wheat MADS box genes

To clarify the function of MADS box genes in wheat (Triticum aestivum L.), we have isolated and characterized cDNA clones corresponding to MADS box genes from wheat. Seven cDNA clones were isolated by screening 2.2x10⁴ plaques of a cDNA library from young spike (3-10 mm in length) using degenerate PCR products of NIADS box region as probes. Each clone contains an open reading frame encoding a putative protein with a MADS box region. Based on the deduced amino acid sequence, seven clones were classified into three groups, i.e., AP1-like (4 clones), AP3-like (2 clones) and AGL6-like (1 clone) groups. Analyses of gene expression patterns suggested that they play different roles in spike/spikelet/floret development in wheat.

S. Ito, Y. Nakahira, T. Shiina and T. Toyoshima (Grad. Schl. Human and Environ. Studies,　Kyoto Univ.)
Circadian expression of a nuclear-encoded chloroplast sigma factor gene in wheat.

The light-responsive promoter (LRP) of the plastid psbD gene encoding photosystem II D2 protein is recognized by the eubacterial-type RNA polymerase (PEP). The level of mRNAs derived from the LRP oscillates diurnally for three cycles in continuous light condition. In vitro transcription in chloroplast extracts revealed that the psbD LRP mRNA level is controlled by an endogenous circadian clock through transcription. In this study, we revealed that mRNA level of a nuclear-encoded chloroplast sigma factor gene (sigA) is controlled by the circadian clock in wheat, that may be involved in the circadian behavior of the psbD LRP.

T. Sugiura, K. Naito, K. Tsunewaki, T. Asahi, and H. Suzuki (Fac. Biosci., Fukui Pref. Univ.)
Repressed expression of the defender against apoptotic cell death 1 (dad1) gene in leaves of necrotic wheat

The dad1 gene is the only identified as an apoptotic cell death suppresser in higher plants. We have cloned an Arabidopsis thaliana dad1 cDNA (Atdad1). We examined the mRNA level of its homologue in leaves of necrotic wheat (Triticum aestivum cv. S-615) that undergoes growth stage specific necrosis caused by two complementary genes, Ne1 and Ne2. We, found that the transcript level was extremely low in the necrotizing region where many dead cells we're histochemically observed, in comparison with the level of control wheat (S-615). This suggests that reduction of the dad1 transcript could be associated with cell demise in necrotic wheat.

T. Koba, T. Suzuki, M. Hayashi and Y. Iguchi (Fac. Hort., Chiba Univ.)
Detection of cDNA fragments responsible for crossability of common wheat with alien ,species by means of Differential Display method

Crossability of common wheat cultivars with alien species are controlled by Kr genetic system. cDNAs were isolated from pistils of cv. Chinese Spring (kr1kr1) and its chromosome substitution lines having chromosome 5B of cvs. Hope and Cheyenne (Kr1Kr1). After amplification of the cDNAs by using combinations of five decamer arbitrary primers, eleven cDNA fragments were found to be specific for chromosome 5B of Hope and Cheyenne, and two were specific for chromosome 5B of Chinese Spring. Some of the fragments are thought to correspond to the gene Kr1. Cloning of the fragments and their characterization are now in progress.

N. Asakura¹, C. Nakamura² and I. Ohtsuka¹ ( ¹Fac. Engineer., Kanagawa Univ., ²Fac. Agr., Kobe Univ.)
Mapping of nucleus-cytoplasm compatibility gene, Ncc-tmp1A, from Triticum timopheevi for the cytoplasm of Aegilops squarrosa and its origin

Tetraploid wheat species have been classified into three groups based on the nuclear compatibility with the cytoplasm of Ae. squarrosa. Nuclear genomes of emmer wheat are incompatible or partially compatible, while nuclear genomes of timopheevi wheat are fully compatible, indicating the presence of nucleus-cytoplasm compatibility (Ncc) gene for the cytoplasm of Ae. squarrosa. Ncc-tmp1A from T. timopheevi was mapped near the centromere of chromosome 1A using (sqr)-Langdon with it. In the nuclear genome of T. timopheevi only Ncc- tmp1A was functional for the cytoplasm of Ae. squarrosa. The origin of Ncc-tmp1A was discussed, comparing with the wheat phylogeny.

Y. Furuta (Fac. Agr., Gifu Univ.)
Propagation properties and flowering habit of Hordeum bulbosum

The wild barley species, Hordeum bulbosum, consists of diploid and autotetraploid cytotypes. In hybrids of H. bulbosum with cultivated barley or wheat, elimination of the bulbosum. chromosomes occurs resulting in haploid plants. H. bulbosum can be propagated both sexually by seeds and vegetatively by bulbs. Its flowering habit is characterized by monoecy but heterogamy, and by female sterile but male fertile lateral florets, which enforce a predominantly out-crossing behavior. However, the male floral organ in the lateral florets contains long filaments and big anthers with a large amount of pollen grains, effecting self-pollination of the male-sterile central florets.

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