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Asano T.,Japan National Institute of Agrobiological Science | Asano T.,University of Tokyo | Hayashi N.,Japan National Institute of Agrobiological Science | Kobayashi M.,Japan National Institute of Agrobiological Science | And 10 more authors.
Plant Journal | Year: 2012

Calcium-dependent protein kinases (CDPKs) regulate the downstream components in calcium signaling pathways. We investigated the effects of overexpression and disruption of an Oryza sativa (rice) CDPK (OsCPK12) on the plant's response to abiotic and biotic stresses. OsCPK12-overexpressing (OsCPK12-OX) plants exhibited increased tolerance to salt stress. The accumulation of hydrogen peroxide (H 2O 2) in the leaves was less in OsCPK12-OX plants than in wild-type (WT) plants. Genes encoding reactive oxygen species (ROS) scavenging enzymes (OsAPx2 and OsAPx8) were more highly expressed in OsCPK12-OX plants than in WT plants, whereas the expression of the NADPH oxidase gene, OsrbohI, was decreased in OsCPK12-OX plants compared with WT plants. Conversely, a retrotransposon (Tos17) insertion mutant, oscpk12, and plants transformed with an OsCPK12 RNA interference (RNAi) construct were more sensitive to high salinity than were WT plants. The level of H 2O 2 accumulation was greater in oscpk12 and OsCPK12 RNAi plants than in the WT. These results suggest that OsCPK12 promotes tolerance to salt stress by reducing the accumulation of ROS. We also observed that OsCPK12-OX seedlings had increased sensitivity to abscisic acid (ABA) and increased susceptibility to blast fungus, probably resulting from the repression of ROS production and/or the involvement of OsCPK12 in the ABA signaling pathway. Collectively, our results suggest that OsCPK12 functions in multiple signaling pathways, positively regulating salt tolerance and negatively modulating blast resistance. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

Yamagishi M.,Hokkaido University | Kishimoto S.,National Institute of Floricultural Science | Nakayama M.,National Institute of Floricultural Science
Plant Breeding | Year: 2010

To elucidate the regulatory mechanisms of carotenoid accumulation in tepals of Asiatic hybrid lily (Lilium spp.), the content and composition of carotenoids and transcriptional changes of carotenoid biosynthetic genes were compared between tepals of yellow, red, pink and white flowers. Yellow and red tepal cultivars accumulated high amounts of carotenoids, and cultivars with pink and white tepals accumulated small amounts of carotenoids. Most of the carotenoids in yellow petals were antheraxanthin, (9Z)-violaxanthin, cis-lutein and violaxanthin. Capsanthin was accumulated in red tepals. Transcription of phytoene synthase, phytoene desaturase, f-carotene desaturase, carotenoid isomerase and b-ring hydroxylase in tepals increased as tepals grew. Among yellow and red tepal cultivars, the amounts of carotenoids were well associated with the transcription levels of biosynthetic genes, indicating that transcription levels regulate carotenoid accumulation in these cultivars. However, in pink and white tepals, the transcription levels of biosynthetic genes were similar to those in red tepals, indicating that small amounts of carotenoids are not explained by down-regulation of biosynthetic genes. Another factor should reduce carotenoid amounts in these tepals. © 2009 Blackwell Verlag GmbH.

Ohmiya A.,National Institute of Floricultural Science
Scientia Horticulturae | Year: 2013

Carotenoids are lipophilic pigments widely distributed in nature. Among pigments produced in plants, carotenoids are unique in that they possess diverse functions depending on the organs and tissues in which they accumulate. The widely varying quantitative and qualitative composition of carotenoids among organs and tissues reflects these diverse functions. The green tissues of most plants show similar carotenoid profiles: Lutein, β-carotene, violaxanthin, neoxanthin, and zeaxanthin, essential components for photosynthesis, are invariably found. In contrast, carotenoid profiles of petals vary among plant species or cultivars and furnish distinct colors ranging from yellow and orange to red that attract pollinators. There is increasing evidence that the carotenoid content of petals is regulated not only by flux through the carotenoid biosynthesis pathway but also by degradation and by sequestration into chromoplasts, which function as sink organelles. These processes are mostly controlled at the transcriptional levels of relevant genes. In this review, the mechanisms that underlie the diverse carotenoid profiles of flowers are summarized with a major focus on molecular events that occur during carotenogenesis in petals. © 2013 Elsevier B.V.

Lai Y.-S.,Hokkaido University | Shimoyamada Y.,Hokkaido University | Nakayama M.,National Institute of Floricultural Science | Yamagishi M.,Hokkaido University
Plant Science | Year: 2012

Anthocyanin biosynthesis is often regulated by MYB transcription factors that are classified into AN2 and C1 subgroups. The AN2 subgroup regulates the late genes in the anthocyanin biosynthesis pathway of eudicots, whereas the C1 subgroup controls both early and late genes in monocots. Anthocyanin is a major pigment in Asiatic hybrid lilies (Lilium spp.), with LhMYB12 being the first AN2 subgroup in monocots. In this study, the accumulation of pigments and gene transcripts during flower bud development was evaluated to determine the genes regulated by LhMYB12. LhMYB12 and anthocyanin biosynthesis genes showed the same transcription profiles, with LhMYB12 directly activating the promoters of chalcone synthase and dihydroflavonol 4-reductase. This indicates that LhMYB12 regulates both early and late genes, despite belonging to the AN2 subgroup. The cultivar Landini accumulated anthocyanin and flavonol. The contents of these pigments increased during the late stages of flower bud development; this might result from the coordinated expression of early and late genes. During the early stages of flower bud development, the tepals contained no flavonoids but accumulated cinnamic acid derivatives. These results indicate that the profiles of pigment accumulation and gene transcription in lily tepals are unique among angiosperm flowers. © 2012 Elsevier Ireland Ltd.

Matsushita Y.,National Institute of Floricultural Science | Usugi T.,Japan National Agricultural Research Center | Tsuda S.,Japan National Agricultural Research Center
European Journal of Plant Pathology | Year: 2011

In situ hybridization was used to analyze the distribution pattern of Tomato chlorotic dwarf viroid (TCDVd) in floral organs of tomato plants. Following TCDVd invasion of floral organs, it became localized only in sepals at an early developmental stage, then reached other floral organs at the flower opening stage, with the exception of part of the placenta and ovules. When distribution of TCDVd was compared with that of Potato spindle tuber viroid (PSTVd), TCDVd was not detected in the outer integument around the embryo sac even though PSTVd was able to invade there, suggesting that such specific distribution might reflect the frequent occurrence of viroid disease on crops caused by PSTVd-seed transmission. © 2011 KNPV.

Yamagishi M.,Hokkaido University | Yoshida Y.,Hokkaido University | Nakayama M.,National Institute of Floricultural Science
Molecular Breeding | Year: 2012

A single dominant locus determines anthocyanin biosynthesis in the tepals of Asiatic hybrid lilies (Lilium spp.); however the gene that determines this trait has not been previously reported. Furthermore, anthocyanin colour hue in tepals varies between cultivars, but the mechanisms underlying this variation are not known. Here, we show that LhMYB12, which is homologous to petunia An2, determines anthocyanin pigmentation in tepals and that the level of LhMYB12 transcription affects the quantity of anthocyanin pigments, producing colour hue variation in tepals. The pink-tepal cultivars Montreux and Renoir were heterozygous for the LhMYB12 gene. Their F 1 population segregated 3:1 for the presence or absence of anthocyanin in tepals, and LhMYB12 cosegregated perfectly with the presence of anthocyanin, indicating that LhMYB12 determines anthocyanin biosynthesis in tepals. Among seven cultivars, a single anthocyanin cyanidin 3-O-β-rutinoside was detected in tepals displaying light pink, pink-red, dark red, or chocolate brown hues. However, concentrations differed according to the following order of colour hue: light pink < pink-red < dark red < chocolate brown, suggesting that colour hue variation in tepals is strongly related to anthocyanin quantities. The accumulation of LhMYB12 transcripts in tepals varied between seven cultivars in the same order, and transcription levels were positively correlated with pigment quantities. This suggests that the levels of transcription of LhMYB12 vary among the different cultivars and subsequently affect the quantities of pigment in tepals. These results indicate that LhMYB12 determines anthocyanin pigmentation and generates the variation in anthocyanin colour hue in lily tepals. © 2011 Springer Science+Business Media B.V.

Sasaki K.,National Institute of Floricultural Science | Yamaguchi H.,National Institute of Floricultural Science | Aida R.,National Institute of Floricultural Science | Shikata M.,National Institute of Floricultural Science | And 2 more authors.
Plant Journal | Year: 2012

Summary We identified a Torenia fournieri Lind. mutant (no. 252) that exhibited a sepaloid phenotype in which the second whorls were changed to sepal-like organs. This mutant had no stamens, and the floral organs consisted of sepals and carpels. Although the expression of a torenia class B MADS-box gene, GLOBOSA (TfGLO), was abolished in the 252 mutant, no mutation of TfGLO was found. Among torenia homologs such as APETALA1 (AP1), LEAFY (LFY), and UNUSUAL FLORAL ORGANS (UFO), which regulate expression of class B genes in Arabidopsis, only accumulation of the TfUFO transcript was diminished in the 252 mutant. Furthermore, a missense mutation was found in the coding region of the mutant TfUFO. Intact TfUFO complemented the mutant phenotype whereas mutated TfUFO did not; in addition, the transgenic phenotype of TfUFO-knockdown torenias coincided with the mutant phenotype. Yeast two-hybrid analysis revealed that the mutated TfUFO lost its ability to interact with TfLFY protein. In situ hybridization analysis indicated that the transcripts of TfUFO and TfLFY were partially accumulated in the same region. These results clearly demonstrate that the defect in TfUFO caused the sepaloid phenotype in the 252 mutant due to the loss of interaction with TfLFY. The Plant Journal © 2012 Blackwell Publishing Ltd.

Ohmiya A.,National Institute of Floricultural Science
ACS Symposium Series | Year: 2013

In chrysanthemums (Chrysanthemum morifolium Ramat.), white petal color is dominant over yellow and is postulated to arise from a single dominant gene that inhibits carotenoid formation. By differential screening, we identified a gene that is expressed specifically in white petals of chrysanthemum. The gene is highly homologous to carotenoid cleavage dioxygenase 4 (CCD4) and was designated CmCCD4a. Suppression of CmCCD4a expression by RNA interference in white-flowered strains resulted in the formation of yellow petals. Flower color mutants with increased levels of carotenoids showed decreased levels of CmCCD4a expression. The results indicate that CmCCD4a is the single dominant gene encoding an enzyme that inhibits carotenoid accumulation in chrysanthemum petals by catalyzing degradation of carotenoids. Although CmCCD4a has been shown to catalyze the conversion of β-carotene to β-ionone in vivo, its catalytic product(s) in planta has not been identified. Involvement of CCD4 in controlling carotenoid content was also examined in petals of white-flowered Ipomoea nil and carnation (Dianthus caryophyllus L.). The results showed that low levels of carotenoids in petals of these plants were not caused by degradation but by low rates of biosynthesis. © 2013 American Chemical Society.

Yamamizo C.,National Institute of Floricultural Science | Kishimoto S.,National Institute of Floricultural Science | Ohmiya A.,National Institute of Floricultural Science
Journal of Experimental Botany | Year: 2010

Japanese morning glory (Ipomoea nil) is a representative plant lacking a yellow-flowered cultivar, although a few wild Ipomoea species contain carotenoids in their petals such as Ipomoea sp. (yellow petals) and I. obscura (pale-yellow petals). In the present study, carotenoid composition and the expression patterns of carotenogenic genes during petal development were compared among I. nil, I. obscura, and Ipomoea sp. to identify the factors regulating carotenoid accumulation in Ipomoea plant petals. In the early stage, the carotenoid composition in petals of all the Ipomoea plants tested was the same as in the leaves mainly showing lutein, violaxanthin, and β-carotene (chloroplast-type carotenoids). However, in fully opened flowers, chloroplast-type carotenoids were entirely absent in I. nil, whereas they were present in trace amounts in the free form in I. obscura. At the late stage of petal development in Ipomoea sp., the majority of carotenoids were β-cryptoxanthin, zeaxanthin, and β-carotene (chromoplast-type carotenoids). In addition, most of them were present in the esterified form. Carotenogenic gene expression was notably lower in I. nil than in Ipomoea sp. In particular, β-ring hydroxylase (CHYB) was considerably suppressed in petals of both I. nil and I. obscura. The CHYB expression was found to be significantly high in the petals of Ipomoea sp. during the synthesis of chromoplast-type carotenoids. The expression levels of carotenoid cleavage genes (CCD1 and CCD4) were not correlated with the amount of carotenoids in petals. These results suggest that both I. obscura and I. nil lack the ability to synthesize chromoplast-type carotenoids because of the transcriptional down-regulation of carotenogenic genes. CHYB, an enzyme that catalyses the addition of a hydroxyl residue required for esterification, was found to be a key enzyme for the accumulation of chromoplast-type carotenoids in petals.

Matsushita Y.,National Institute of Floricultural Science | Usugi T.,Japan National Agricultural Research Center | Tsuda S.,Japan National Agricultural Research Center
European Journal of Plant Pathology | Year: 2010

Potato spindle tuber viroid (PSTVd) and Tomato chlorotic dwarf viroid (TCDVd) are two closely related Pospiviroids which cause economically important diseases on tomato (Solanum lycopersicum). Until now, however, there have been no molecular diagnostic methods available for discriminating between them except sequencing. We have developed a multiplex reverse transcription-polymerase chain reaction (RT-PCR) system that simultaneously detects and discriminates between both viroids in one reaction. Using this system, amplified cDNAs resulted in a 271 bp PCR product when PSTVd is detected as the template and 191 bp when TCDVd is detected. This multiplex RT-PCR system was used to accurately detect both viroids in field cultivated tomato and petunia (Petunia × hybrida) plants. This is the first finding of PSTVd in field grown tomatoes in Japan. © 2010 KNPV.

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