Genetic and biochemical analyzes of an accelerated internode overgrowth mutant in rice.

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A rice internode overgrowth mutant, awa-odori (AO) was induced from a japonica cultivar, Koshi-hikari by gamma-ray seed irradiation. The slender shoot phenotype alike in seedlings infected by "bakanae" disease caused by Gibberella fujikuroi has been expressed by a recessive gene named ao-1(accelerated internode overgrowth 1). The results of examination on responsibility of mutant seedlings to some combined applications of GA_3 and its retardant, Uniconazole suggested that this characteristics of the mutant is not caused by an over product of endogenous gibberellins as shown in "bakanae" disease.Double mutant analysis with two cross combinations of AO (ao-1) x Kotake-tamanishiki (d-18) and AO (ao-1) x Tangin-bozu(d-35) also supported this suggestion.The result of analysis on sugar components of shoot showed that sugar contents of hemicellulose I and cellulose fractions increased significantly in the mutant compared with Koshi-hikari.Two-dimensional analysis of soluble and cell wall proteins extracted from the basal area of seedling shoot of AO mutant and Koshi-hikari was carried out and some specific protein spots in the mutant were detected from both 2D-PAGEs.205 sequenced clones in the cDNA library isolated from mRNAs extracted from elongating internodes of AO shoot were researched on the homology to the other nuclertide sequences using DNA-database of Blastn E-mail Server (NCBI) and DNASIS-MAC (Hitachi Software Engineering Co., Ltd.). The result showed that 41 clones among them encoded a partial homology (>40% in the amino acid sequence level) to DNA sequences recorded in the databases.Further experiment for cloning ao-1 gene is now being continued.