Rice plants (Oryza sativa L cv Akitakomachi) were grown under free-air CO 2 enrichment (FACE) in farmers' fields in Shizukuishi, Iwate, Japan during 1999 and 2000. The grains were harvested and subsequently analyzed for protein and amylose contents as well as the traits related to cooked-rice viscosity. The cooked rice was also subjected to sensory evaluation. The protein content of rice grains grown under elevated CO 2 was significantly lower than that of rice grown under ambient conditions. In addition, CO 2 enrichment increased the whiteness of the grains in both brown and milled rice and reduced their surface hardness. Although the amylose content of rice grains was unaffected, starch pasting properties demonstrated that rice grains in elevated CO 2 had higher maximum viscosity and breakdown than those grown in ambient conditions. Sensory evaluation of cooked rice with respect to umami (deliciousness), appearance, aroma, hardness, stickiness and overall palatability index indicated that the sensory properties were not significantly altered by the CO 2 enrichment treatment. Therefore, we conclude that the growth of the rice cultivar Akitakomachi under elevated CO 2 concentration decreased the protein content, but did not change the palatability to a level that may be detected by sensory taste panel evaluation.

Rice production is a substantial source of atmospheric CH 4 , which is second only to CO 2 as a contributor to global warming. Since CH 4 is produced in anaerobic soil environments, water management is expected to be a practical measure to mitigate CH 4 emissions. In this study, we used a process-based biogeochemistry model (DNDC-Rice) to assess the CH 4 mitigation potentials of alternative water regimes (AWR) for rice fields at a regional scale. Before regional application, we tested DNDC-Rice using site-scale data from three rice fields in Japan with different water regimes. The observed CH 4 emissions were reduced by drainage of the fields, but were enhanced by organic amendments. DNDC-Rice gave acceptable predictions of variation in daily CH 4 fluxes and seasonal CH 4 emissions due to changes in the water regime. For regional application, we constructed a GIS database at a 1 Â 1 km mesh scale that contained data on rice field area, soil properties, daily weather, and farming management of each cell in the mesh, covering 3.2% of the rice fields in Japan's Hokkaido region. We ran DNDC-Rice to simulate CH 4 emissions under five simulated water regimes: the conventional water regime and four AWR scenarios with gradually increasing drainage. We found that AWR can reduce CH 4 emission by up to 41% compared with the emission under conventional water regime. Including the changes in CO 2 and nitrous oxide emissions, potential mitigation of greenhouse gas (GHG) was 2.6 Mg CO 2 Eq. ha À1 yr À1 . If this estimate is expanded to Japan's total rice fields, expected GHG mitigation is 4.3 Tg CO 2 Eq. yr À1 , which accounts for 0.32% of total GHG emissions from Japan. For a reliable national-scale assessment, however, databases on soil, weather, and farming management must be constructed at a national scale, as these factors are widely variable between regions in Japan.

Our preliminary clinical trial showed that consumption of cooked rice of a Japanese common cultivar Yukihikari improved atopic dermatitis associated with a suspected rice allergy, although the underlying mechanisms remain unclear. We hypothesised that the ameliorating effect of Yukihikari on atopic dermatitis is associated with the gut microbiota. BALB/c mice were fed a synthetic diet supplemented with uncooked and polished white rice powder prepared from one of four different cultivars: Yukihikari, rice A (common rice), rice B (brewery rice) and rice C (waxy rice). Denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene fragments showed that the composition of faecal microbiota was different between mice fed Yukihikari and those fed rice A. Analysis of the 16S rRNA clone library and species-specific realtime PCR showed that the abundance of Akkermansia muciniphila, a mucin degrader, tended to be lower in mice fed Yukihikari. The incidence of allergic diarrhoea induced by oral administration of ovalbumin in systemically immunised mice was lower in mice fed Yukihikari, albeit with no difference in serum antibodies specific to ovalbumin. In a separate experiment, serum antibody levels specific to orally administered ovalbumin were lower in mice fed Yukihikari. Additionally, the translocation of horseradish peroxidase in isolated segments of ileum and colon tended to be lower in mice fed Yukihikari, suggesting a reduction in gut permeability in mice fed Yukihikari. These data indicate that changes in the gut microbiota of mice fed Yukihikari could be advantageous in the prevention of food allergy. Rice: Allergy: Gut microbiota: MiceRice seed is a cereal consumed in large quantities around the world and is a staple foodstuff in most countries in South and East Asia. So far, several clinical studies have shown that IgEmediated allergy against rice was associated with a subset of patients with atopic dermatitis (AD) in Japan (1 -3) . Additionally, since Shibasaki et al.(4) first described that a high degree of allergenicity was found in a globulin fraction of rice seed proteins (4) , many studies have reported on rice allergenic proteins (5 -9) . Although avoidance of the intake of allergens is generally one of the emphasised therapeutic suggestions for allergy, it is impractical to strictly remove rice and its products from Asian diets, including that of Japan. Therefore, attempts have been made to eliminate allergenic rice proteins by protease treatment (10) , high-pressure treatment (11) and antisense transgene expression (12) . We previously performed a small-scale prospective open clinical trial to examine the effects of consuming Yukihikari, a common rice cultivar developed by the Hokkaido Central Agricultural Experiment Station in Japan, on AD patients with a suspected rice allergy. A total of thirtyeight patients with a mean age of 5·09 (range 0-38) years were enrolled in the trial and fed Yukihikari as their staple food for 4 weeks. The clinical skin score was improved in twenty-six patie...

Starch, the major component of cereal grains including rice is composed of two types of α-polyglucan, amylose and amylopectin. Amylose forms a mainly linear structure, with glucose residues linked via α-1,4 bonds, whereas amylopectin has a highly ordered structure 1) with numerous branches linked to the middle of the linear structure by α-1,6 bonds. The ratio of amylose to amylopectin and the characteristics of the distribution of amylopectin chain-lengths affect the eating qualities and processing properties of cereal-based foods through changes in gelatinization and retrogradation of starch. Natural and induced mutants that have a defect in a gene encoding a starch-synthesizing enzyme and altered starch properties have been utilized in food production. For example, traditionally cultivated waxy rice, waxy maize, waxy barley, and the relatively recently bred waxy wheat 2) , which lack the granule-bound starch synthase I (GBSSI or Waxy) responsible for amylose synthesis have stickier or softer textures after cooking, and have been utilized for food products where such textures are desirable. In case of the rice mutants lacking starch branching enzyme IIb activity (amylose-extender or ae), the proportion of short-chains (degree of polymerisation (DP) 17 or less) of amylopectin is decreased and that of middle-length chains (DP 18 to 36) is increased, which results in higher gelatinization temperatures (GTs) and faster retrogradation of gelatinazed starch.3) This type of maize is known as amylomaize and is utilized for the production of resistant starch 4) : i.e., starch that cannot be digested by the human small intestine and therefore acts as a dietary fiber with many health benefits. Lack of starch synthase IIa (SSIIa) function causes changes in chain-length distribution: in rice, 5) barley, 6) wheat 7) and maize, 8) there is an

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