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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

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. Source

Ohmiya A.,National Institute of Floricultural Science
Scientia Horticulturae

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. Source

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

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. Source

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

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. Source

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

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. Source

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