Molecular genetic analysis of flower coloration in the Japanese morning glory

森田, 裕将; モリタ, ヤスマサ; MORITA, Yasumasa

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Molecular genetic analysis of flower coloration in the Japanese morning glory

https://ir.soken.ac.jp/records/1055

名前 / ファイル	ライセンス	アクション
要旨・審査要旨 (372.5 kB)

Item type

学位論文 / Thesis or Dissertation(1)

公開日

2010-02-22

タイトル

Molecular genetic analysis of flower coloration in the Japanese morning glory

タイトル

Molecular genetic analysis of flower coloration in the Japanese morning glory

言語

eng

資源タイプ

資源タイプ識別子

http://purl.org/coar/resource_type/c_46ec

資源タイプ

thesis

著者名

森田, 裕将

フリガナ

モリタ, ヤスマサ

著者

MORITA, Yasumasa

学位授与機関

学位授与機関名

総合研究大学院大学

学位名

博士（理学）

学位記番号

内容記述タイプ

Other

内容記述

総研大乙第161号

研究科

値

生命科学研究科

専攻

値

19 基礎生物学専攻

学位授与年月日

2006-03-24

学位授与年度

値

2005

要旨

内容記述タイプ

Other

内容記述

The genus Ipomoea includes approximately 600 species distributed on a worldwide scale that are characterized by a diversity of floral morphologies and coloration pattern. Most Ipomoea species can be found in the Americas, particularly in Mexico, and those widely distribution are covered with the Pacific basin and Africa, Asia and Australia.　The genus Ipomoea can be divided into following three subgenuses,Eriospermum, Ipomoea and Calystegia.　Among the subgenus Ipomoea, three morning glories, I. nil (the Japanese morning glory) with blue flowers, I. purpurea (the common morning glory) with dark purple flowers, and I. tricolor with blue flowers, were domesticated well as ornamental plants, and many mutants displaying various flower colors were isolated.　The blue flowers of I. nil and I. tricolor contain a polyacylatyed cyanidin-based anthocyanin, termed Heavenly Blue Anthocyanin(HBA), as a major pigment, whereas the dark purple flowers of I. purpurea contains a cyanidin derivative that lacks a methyl residue and one glucose molecule from HBA.
　　The Japanese morning glory had been introduced into Japan from China as a medical herb approximately in the 8th century, and a number of spontaneous mutants displaying various flower colors have been isolated since the 17th century.　According to the classical genetic studies, mutations affecting flower pigmentations can be classified mainly into three categories: mutations conferring white flowers, mutations affecting blue flower coloration, and mutations influencing flower hue.　Mutations conferring white flowers can be classified into four groups, a, c, ca, and r; the a, and r mutants exhibit white flowers with green stems and normal-colored black seeds, and the c mutants display white flowers with red stems and normal-colored seeds, while the ca mutants produce white flowers with green stem and ivory seeds.　 Blue　flower coloration was regarded to be mainly controlled by two genetic loci, Magenta and Purple.　Recessive magenta and purplemutants bloom magenta and purple flowers, respectively, and double mutants carrying both magenta and purple alleles display red flowers.　 Three loci, Dusky, Duskish and Dingy, control flower hue, and recessive mutations in one of these loci confer dull colored flowers.
　　The anthocyanin biosynthesis pathway is well documented, and the genes for anthocyanin biosymthesis can be divided between structural genes for enzymes involved in anthocyanin biosynthesis and regulatory genes for transcription factors acting on the structural genes. The structural genes encoding enzymes to produce anthocyanidin 3-O-glucsides, which are the first major stable colored pigments in the anthocyamin biosynthesis pathway have been identified and characterized.　Further modifications of　anthocyanidin 3-O-glucsides including glycosylation, acylation, and methylation can occur in a species-specific manner, although only limited information about the genes responsible for these modification processes is available.　 The transcriptional regulators encoded by the regulatory genes are known to include members of proteins containing an R2R3-MYB domain, a bHLH (basic helix-loop-helix) domain, and conserved WD40 repeats (WDRs), and the combinations of the R2R3-MYB, bHLH, and WDR factors and their interactions determine the set of genes to be expressed.　Among the mutations affecting flower pigmentations,a and r such as a-3, andr-1and r-3 are mutations in the structural genes encoding dihydroflavonol 4-reductase (DFR), chalcone synthase (CHS) and anthosyanidin synthase (ANS), respectively. 　For the genes controlling blue flower coloration, thePurple gene was shown to be NHX1 encoding a vacuolar Na+ / H+ exchanger, which is responsible for increasing vacuolar pH in the petals during flower opening.
　　In this dissertation, he briefly introduced flower pigmentation of three morning glories, I. nil, I. purpurea, and I. tricolor, the genes for biosynthesis of anthocyanin pigments, and the I. nil spontaneous mutations that control the flower coloration. 　In Chapter 2, he described that spontaneous mutations in F3'H, magenta, pink, and fuchsia, conferring reddish flowers are shown to be a nonsense mutation caused by a single C to T base transition generating the TGA stop codon in I. nil, an insertion mutation caused by 0.55-kb DNA transpon Tip201 belonging to the hAT superfamily in I. purpurea, and a single T insertion generating the stop codon TAG in I. tricolor, respectively.　Although various plants exhibiting reddish flowers are postulated to carry mutations controlling the F3'H activity, none of them have been identified and only a few F3'H mutations identified are those affecting seed coloration;the tt7 mutation in Arabidopsis conferring pale brown
seeds and reduced anthocyanin content to the whole plant is caused by a single C to T base transition generating the stop codon TAA, and the recessive t mutant in soybean affecting pigmentation in its seed coats and trichome hairs is a frameshift (a single C deletion) mutation. Therefore, the characterization of the magenta, pink, and fuchsia mutations in these three moming glories were the first report on the mutation in the F3'H gene conferring reddish flowers.　In Chapter 3, he described that the dusky, mutation in I. nil conferring reddish-brown or purplish-grey hue in the petals are frameshift mutations caused by 4-bp insertions at an identical position near the 3’end of the 3GGT gene for a novel glucosyltransferase, UDP-glucose:anthocyanidin 3-O- lucoside-2" -O-glucosyltransferase, which mediates the glucosylation of anthocyanidin3-O-glucosides to yield anthocyanidin 3-O-sophorosides. Except for the 3GGT gene described here, there has been only one gene, whose mutation is characterized in the genes mediating an addition of a sugar residue to the glucose molecule of anthocyanidin 3-O-glucosides; the petumia Rt gene encoding UDP-rhamnose:anthocyanidin 3-O-glucoside-6" -O-rhamnosyltransferase (3RT), which controls the conversion of anthocyanidin 3-O-glucosides into anthocyamidin 3-0-rutinosides.
    In Chapter 4, he first charancterized the tissue-specific expression of three MYB genes, three bHLH genes, and two WDR genes in I.nil. 　Subsequently, he showed that the c and ca mutations are frameshift mutations caused by a 2-bp deletion and 7-bp insertions in the genes for the R2R3-MYB and WDR transcriptional regulators designated as MYB 1 and WDR 1, respectively.　In addition to defects in flower, stem, and seed pigmentations, he also found that the ca mutants show reduced trichome formation in seeds, which is a novel epidermal traits associated with the transcriptional factors.
　　Based on these results, he also discusses in Chapter 5 that the three morning glories, I. nil, I. purpurea, and I. tricolor, can collectively serve good models for the elucidation of anthocyan in pigmentation in the flowers, because the identified mutations affecting flower pigmentation in these Ipomoea are comparable with or slightly exceed the characterized mutations flower coloration in petunia, which is regarded to be a model plant for flower pigmentation.

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Molecular genetic analysis of flower coloration in the Japanese morning glory

× 森田, 裕将

× モリタ, ヤスマサ

× MORITA, Yasumasa

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