Detection of quantitative trait loci controlling pre-harvest sprouting resistance by using backcrossed populations of japonica rice cultivars

Backcrossed inbred lines (BILs) and a set of reciprocal chromosome segment substitution lines (CSSLs) derived from crosses between japonica rice cultivars Nipponbare and Koshihikari were used to detect quantitative trait loci (QTLs) for pre-harvest sprouting resistance. In the BILs, we detected one QTL on chromosome 3 and one QTL on chromosome 12. The QTL on the short arm of chromosome 3 accounted for 45.0% of the phenotypic variance and the Nipponbare allele of the QTL increased germination percentage by 21.3%. In the CSSLs, we detected seven QTLs, which were located on chromosomes 2, 3 (two), 5, 8 and 11 (two). All Nipponbare alleles of the QTLs were associated with an increased rate of germination. The major QTL for pre-harvest sprouting resistance on the short arm of chromosome 3 was localized to a 474-kbp region in the Nipponbare genome by the SSR markers RM14240 and RM14275 by using 11 substitution lines to replace the different short chromosome segments on chromosome 3. This QTL co-localized with the low-temperature germinability gene qLTG3-1. The level of germinability under low temperature strongly correlated with the level of pre-harvest sprouting resistance in the substitution lines. Sequence analyses revealed a novel functional allele of qLTG3-1 in Nipponbare and a loss-of-function allele in Koshihikari. The allelic difference in qLTG3-1 between Nipponbare and Koshihikari is likely to be associated with differences in both pre-harvest sprouting resistance and low-temperature germinability

Natural Variation in the Flag Leaf Morphology of Rice Due to a Mutation of the NARROW LEAF 1 Gene in Oryza sativa L.

We investigated the natural variations in the flag leaf morphology of rice. We conducted a principal component analysis based on nine flag leaf morphology traits using 103 accessions from the National Institute of Agrobiological Sciences Core Collection. The first component explained 39% of total variance, and the variable with highest loading was the width of the flag leaf (WFL). A genome-wide association analysis of 102 diverse Japanese accessions revealed that marker RM6992 on chromosome 4 was highly associated with WFL. In analyses of progenies derived from a cross between Takanari and Akenohoshi, the most significant quantitative trait locus (QTL) for WFL was in a 10.3-kb region containing the NARROW LEAF 1 (NAL1) gene, located 0.4 Mb downstream of RM6992. Analyses of chromosomal segment substitution lines indicated that a mutation (G1509A single-nucleotide mutation, causing an R233H amino acid substitution in NAL1) was present at the QTL. This explained 13 and 20% of total variability in WFL and the distance between small vascular bundles, respectively. The mutation apparently occurred during rice domestication and spread into japonica, tropical japonica, and indica subgroups. Notably, one accession, Phulba, had a NAL1 allele encoding only the N-terminal, or one-fourth, of the wild-type peptide. Given that the Phulba allele and the histidine-type allele showed essentially the same phenotype, the histidine-type allele was regarded as malfunctional. The phenotypes of transgenic plants varied depending on the ratio of histidine-type alleles to arginine-type alleles, raising the possibility that H(233)-type products function differently from and compete with R(233)-type products

Enhancing effects of salicylate on tonic and phasic block of Na+ channels by class 1 antiarrhythmic agents in the ventricular myocytes and the guinea pig papillary muscle

AbstractObjective: To study the interaction between salicylate and class 1 antiarrhythmic agents. Methods: The effects of salicylate on class 1 antiarrhythmic agent-induced tonic and phasic block of the Na+ current (INa) of ventricular myocytes and the upstroke velocity of the action potential (Vmax) of papillary muscles were examined by both the patch clamp technique and conventional microelectrode techniques. Results: Salicylate enhanced quinidine-induced tonic and phasic block of INa at a holding potential of −100 mV but not at a holding potential of −140 mV; this enhancement was accompanied by a shift of the h∞ curve in the presence of quinidine in a further hyperpolarized direction, although salicylate alone did not affect INa. Salicylate enhanced the tonic and phasic block of Vmax induced by quinidine, aprindine and disopyramide but had little effect on that induced by procainamide or mexiletine; the enhancing effects were related to the liposolubility of the drugs. Conclusions: Salicylate enhanced tonic and phasic block of Na+ channels induced by class 1 highly liposoluble antiarrhythmic agents. Based on the modulated receptor hypothesis, it is probable that this enhancement was mediated by an increase in the affinity of Na+ channel blockers with high lipid solubility to the inactivated state channels

サイエンス ショップ ノ キョウイクテキ イギ ショート ターム リサーチ ノ シンチョク ジョウキョウ

第2 部 コミュニケーションデザイン論集論文・実践報

ショウワキチ ト ドームフジキチ ニ オケル エアロゾル リュウケイ ブンプ ノ ツウネン カンソク

1997年2月～1998年1月に,昭和基地(69゜00′S,39゜35′E,15 m a.s.l.)及びドームふじ観測拠点(77゜19′S,39゜42′E,3810 m a.s.l.)において,直径0.003-5 μmのエアロゾル粒径分布の変動の観測を行った.両基地において小エイトケンモード(直径0.05 μm以下),大エイトケンモード(直径0.05-0.3 μm),大粒子・粗大粒子モード(直径0.3 μm以上)の3つのモードが認められた.小エイトケンモードおよび大エイトケンモードは,夏に高濃度,冬に低濃度となり,一方,大粒子・巨大粒子モードは夏に低濃度,冬に高濃度となった.1～数日の時間スケールの全粒径にわたる急増,急減現象が両基地で冬季に見られた.ドームふじ観測拠点では春季に小エイトケン粒子のみの急増も見られた.ドームふじ観測拠点においてこれらの現象が起こる気象条件は,昭和基地における類似の現象が起こる時の気象条件とは異なっていた.Simultaneous observations of the aerosol size distribution for diameters of 0.003-5.0 μm were performed at Syowa Station (69゜00′S, 39゜35′E, 15 m a.s.l.) and Dome Fuji Station (77゜19′S, 39゜42′E, 3810 m a.s.l.) in Antarctica from February 1997 to January 1998. Size distributions show composites of a small-Aitken mode (less than 0.05 μm in diameter), a large-Aitken mode (0.05-0.3 μm in diameter), and a large giant particle mode (larger than 0.3 μm in diameter). Concentrations of small and large Aitken modes were high in summer and low in winter. On the other hand, concentrations of large giant particle mode were low in summer and high in winter. The high and or low concentration events for one or a few days in whole size range were observed especially in winter. High concentration events in small Aitken mode with the low concentrations in diameter of 0.07-5.0 μm were also observed at Dome Fuji Station in spring. Meteorological conditions during the events at Dome Fuji Station were different from those at at Syowa station

Starch biosynthesis in rice endosperm requires the presence of either starch synthase I or IIIa

Starch synthase (SS) I and IIIa are the first and second largest components of total soluble SS activity, respectively, in developing japonica rice (Oryza sativa L.) endosperm. To elucidate the distinct and overlapping functions of these enzymes, double mutants were created by crossing the ss1 null mutant with the ss3a null mutant. In the F2 generation, two opaque seed types were found to have either the ss1ss1/SS3ass3a or the SS1ss1/ss3ass3a genotype. Phenotypic analyses revealed lower SS activity in the endosperm of these lines than in those of the parent mutant lines since these seeds had different copies of SSI and SSIIIa genes in a heterozygous state. The endosperm of the two types of opaque seeds contained the unique starch with modified fine structure, round-shaped starch granules, high amylose content, and specific physicochemical properties. The seed weight was ∼90% of that of the wild type. The amount of granule-bound starch synthase I (GBSSI) and the activity of ADP-glucose pyrophosphorylase (AGPase) were higher than in the wild type and parent mutant lines. The double-recessive homozygous mutant prepared from both ss1 and ss3a null mutants was considered sterile, while the mutant produced by the leaky ss1 mutant×ss3a null mutant cross was fertile. This present study strongly suggests that at least SSI or SSIIIa is required for starch biosynthesis in rice endosperm