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Akita Y.,Japan Atomic Energy Agency | Ishizaka H.,Saitama Prefecture Agriculture and Forestry Research Center | Nakayama M.,Japan National Agriculture and Food Research Organization | Shimada A.,Japan Atomic Energy Agency | And 4 more authors.
Journal of Horticultural Science and Biotechnology

The flower colour of Cyclamen graecum gra6 (wild-type) is pink-purple in the main part of the petal, referred to as the 'slip', and deep purple at the petal base, referred to as the 'eye'. On the other hand, flowers of C. graecum gra50 (a white-flowered variant) exhibit a white colour in both the 'slip' and 'eye' regions. In this study, the relationship between floral pigmentation and the expression of several anthocyanin biosynthesis genes was investigated in C. graecum gra6 and gra50.The pigments in the 'slip' and 'eye' regions consist mainly of malvidin 3,5-diglucoside in gra6, suggesting that the difference between the colour of the 'slip' and 'eye' regions is related to the amount of anthocyanin present.White-flowered C. graecum gra50 possessed lower amounts of anthocyanins, but higher amounts of flavonols compared to gra6, suggesting a change in metabolism caused by a disruption of anthocyanin biosynthesis. Gene expression analysis demonstrated that expression of the dihydroflavonol 4-reductase gene 2 (CgraDFR2) was lower in gra50 compared with gra6, whereas expression of the three other key genes (dihydroflavonol 4-reductase gene 1, flavonoid 3',5'-hydroxylase, and anthocyanidin synthase) did not differ greatly. These results suggest that the whiteflowered variant (gra50) may result from a defect in expression of the CgraDFR2 gene. Source

Kitamura S.,Japan Atomic Energy Agency | Akita Y.,Japan Atomic Energy Agency | Ishizaka H.,Saitama Prefecture Agriculture and Forestry Research Center | Narumi I.,Japan Atomic Energy Agency | Tanaka A.,Japan Atomic Energy Agency
Journal of Plant Physiology

Anthocyanins are a subclass of flavonoids and are a major contributor to flower colors ranging from red to blue and purple. Previous studies in model and ornamental plants indicate a member of the glutathione S-transferase (GST) gene family is involved in vacuolar accumulation of anthocyanins. In order to identify the anthocyanin-related GST in cyclamen, degenerate PCR was performed using total RNA from immature young petals. Four candidates of GSTs (CkmGST1 to CkmGST4) were isolated. Phylogenetic analysis indicated that CkmGST3 was closely related to PhAN9, an anthocyanin-related GST of petunia, and this clade was clustered with other known anthocyanin-related GSTs. Expression analysis at different developmental stages of petals revealed that CkmGST3 was strongly expressed in paler pigmented petals than in fully pigmented petals, in contrast to the constitutive expression of the other three candidates during petal development. This expression pattern of CkmGST3 was correlated with those of other anthocyanin biosynthetic genes such as CkmF3'5'H and CkmDFR2. Molecular complementation of Arabidopsis tt19, a knockout mutant of an anthocyanin-related GST gene, demonstrated that CkmGST3 could complement the anthocyanin-less phenotype of tt19. Transgenic plants that expressed the other three CkmGSTs did not show anthocyanin accumulation. These results indicate CkmGST3 functions in anthocyanin accumulation in cyclamen. © 2011 Elsevier GmbH. Source

Kuwagata T.,Japan National Institute for Agro - Environmental Sciences | Ishigooka Y.,Japan National Institute for Agro - Environmental Sciences | Fukuoka M.,Japan National Institute for Agro - Environmental Sciences | Yoshimoto M.,Japan National Institute for Agro - Environmental Sciences | And 3 more authors.
Scientific Online Letters on the Atmosphere

The seasonal (monthly) variation in temperature difference between a meteorological station in an urban-area and nearby farmland in Kumagaya City was examined over 2010-2012. Kumagaya, one of the hottest cities in Japan, has an urban area of about 5 × 5 km and is surrounded by farmland. The daily mean, maximum, and minimum temperatures (Tmean, Tmax, and Tmin) routinely observed at the meteorological station (urban site) were higher than at the nearby farmland site across all seasons. Differences in the monthly temperatures between the two sites were 0.17-0.90°C (Tmean), 0.55-1.63°C (Tmax), and 0.20-0.62°C (Tmin), and the maximum differences were in August (Tmean and Tmax) and April (Tmin). Large temperature differences (> 1°C) for Tmax were observed during the paddy rice-growing season in farmland from July to September. Differences in daily Tmax and Tmean between the two sites were found to increase with daily solar radiation Sd. The sensitivities of these temperature differences to Sd were larger from July to September. The number of "extremely hot days" (Tmax ≥ 35°C) at the farmland site was only 36% of the number at the urban site, while the relative proportion of "sultry nights" (Tmin ≥ 25°C) was 62%. © 2014, the Meteorological Society of Japan. Source

Nakaune M.,Saitama Prefecture Agriculture and Forestry Research Center | Nakaune M.,University of Tsukuba | Hanada A.,RIKEN | Yin Y.-G.,University of Tsukuba | And 3 more authors.
Plant Physiology and Biochemistry

Seed germination is the initial step of plant development. Seed priming with salt promotes seed germination in tomato (Solanum lycopersicum L.); however, the molecular and physiological mechanisms underlying the enhancement of seed germination by priming remain to be elucidated. In this study, we examined the following in seeds both during and after priming treatment: the endogenous abscisic acid (ABA) and gibberellin (GA) concentrations; the expression of genes encoding ABA catabolic and GA biosynthesis enzymes, including 8'-hydroxylase (CYP707A), copalyl diphosphate synthase (CPS), GA 20-oxidase (GA20ox) and GA 3-oxidase (GA3ox); and endosperm cap weakening enzymes, including expansin (EXP), class I β-1,3-glucanase (GulB), endo-β-mannanase (MAN) and xyloglucan endotransglucosylase (XTH). Tomato seeds were soaked for 24h at 25°C in the dark in 300mM NaCl (NaCl-priming) or distilled water (hydro-priming). For both priming treatments, the ABA content in the seeds increased during treatment but rapidly decreased after sowing. Both during and after the priming treatments, the ABA levels in the hydro-primed seeds and NaCl-primed seeds were not significantly different. The expression levels of SlGA20ox1, SlGA3ox1 and SlGA3ox2 were significantly enhanced in the NaCl-primed seeds compared to the hydro-primed seeds. The GA4 content was quantifiable after both types of priming, indicating that GA4 is the major bioactive GA molecule involved in tomato seed germination. The GA4 content was significantly higher in the NaCl-primed seeds than in the hydro-primed seeds 12h after sowing and thereafter. Additionally, the peak expression levels of SlEXP4, SlGulB, SlMAN2 and SlXTH4 occurred earlier and were significantly higher in the NaCl-primed seeds than in the hydro-primed seeds. These results suggest that the observed effect of NaCl-priming on tomato seed germination is caused by an increase of the GA4 content via GA biosynthetic gene activation and a subsequent increase in the expression of genes related to endosperm cap weakening. © 2011 Elsevier Masson SAS. Source

Masutomi Y.,Ibaraki University | Masutomi Y.,Center for Environmental Science in Saitama | Arakawa M.,Saitama Prefecture Agriculture and Forestry Research Center | Minoda T.,Saitama Prefecture Agriculture and Forestry Research Center | And 2 more authors.
Agricultural and Forest Meteorology

A high incidence of chalky rice kernels (CRKs), caused mainly by a high air temperature during the grain-filling period, has become a significant problem for rice production in Japan. Adding to the problem, global warming will increase the incidence of CRKs into the future. The objective of this study is to quantify two parameters that represent basic characteristics of the incidence of CRKs: Tcr, the critical air temperature at which CRKs begin to occur; and St, the sensitivity of the incidence to air temperature changes above Tcr. We quantify these two parameters for three groups of CRKs, into which all five types of CRKs can be divided: white-back and white-belly (BAB); white-based (BSD); and milky-white and white-core (MAC). To quantify the parameters, we first propose a simple statistical model that includes Tcr and St. Then, using field experimental data, we statistically quantify them according to the three groups of CRKs. The rice cultivar used in this study is "Sai-no-kagayaki." The results showed that Tcrs for BAB, BSD, and MAC were 27.28°C, 25.13°C, and 25.05°C, respectively. The corresponding values of Sts were 10.51%/°C, 10.28%/°C, and 2.61%/°C. From these results, BSD and MAC occur at an air temperature about 2°C lower than BAB does, and BAB and BSD have sensitivity to air temperature changes about four-fold that of MAC. Thus, BSD has both a lower critical air temperature and a higher sensitivity to air temperature changes. These characteristics can explain the observed high incidence of BSD in the past and at present. Estimations of the incidences of CRKs using the proposed model with the quantified parameters show that the incidence in BSD is likely to continue to be higher than in the other types even in the early stages of a warmer future under global warming. © 2014 Elsevier B.V. Source

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