日本の在来トウガラシ(<i>Capsicum annuum</i>)における非辛味性は <i>Pun1</i> 遺伝子の新規機能欠損アリルに起因する Non-pungency in a Japanese Chili Pepper Landrace (<i>Capsicum annuum</i>) is Caused by a Novel Loss-of-function <i>Pun1</i> Allele

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Abstract

<p>トウガラシの辛味はカプサイシノイドと総称される辛味成分による.この成分は,トウガラシで特異的に生合成される成分であり,辛味性は putative acyltransferase をコードする <i>Pun1</i> 遺伝子によって質的に制御されている.<i>Pun1</i> 遺伝子の変異は,非辛味性を引き起こすことが知られている.これまでに3つの機能欠損アリル(<i>pun1</i><sup>1–3</sup>)が報告されているが,そのアリルの多様性は十分に明らかにされていない.本研究では,わが国在来の甘トウガラシ'奈良紫'から新規の機能欠損 <i>pun1</i> アリル(<i>pun1</i><sup>4</sup>)を見出した.<i>Pun1</i> 遺伝子の塩基配列解析により,この新規アリルでは第 2 エキソンでアデニン 1 塩基の挿入が生じていることを明らかにした.この 1 塩基挿入は'奈良紫'に特異的であり,野生型には存在しない.この挿入は,フレームシフト変異を引き起こし,短縮タンパクを生じさせる.遺伝子発現解析の結果,<i>Pun1</i> は辛味品種で強く発現していたのに対して,'奈良紫'ではほとんど発現していなかった.'奈良紫'と辛味品種の F<sub>2</sub> 集団(n = 103)において,<i>pun1</i><sup>4</sup> 遺伝子型と非辛味性は完全に共分離した.'奈良紫'と <i>pun1</i><sup>4</sup> アリルを判別する DNA マーカ−は,甘トウガラシの栽培化過程を理解する上で有用な知見を与えるだろう.</p>

<p>Pungency in peppers is due to the presence of the alkaloid capsaicin and its analogues, collectively known as capsaicinoids. These compounds are only produced in the <i>Capsicum</i> genus and function as deterrents to mammals from consuming the pepper fruits. Pungency in pepper is qualitatively controlled by the <i>Pun1</i> locus, which encodes a putative acyltransferase enzyme. Mutations in the <i>Pun1</i> gene result in a loss of pungency, and several <i>Pun1</i> loss-of-function alleles have been identified in sweet peppers to date (<i>pun1</i><sup>1–3</sup>). However, variations in <i>pun1</i> alleles have not been completely elucidated. In the present study, we report a new type of loss-of-function <i>pun1</i> allele, named <i>pun1</i><sup>4</sup>, in a Japanese sweet pepper cultivar, 'Nara Murasaki' (<i>C. annuum</i>). Sequence analysis at the <i>Pun1</i> locus revealed that this type of <i>Pun1</i> allele is caused by a single adenine nucleotide insertion in the second exon region. This insertion is unique to 'Nara Murasaki' and is not present in wild-type <i>Pun1</i>. This insertion causes a frameshift mutation and a change in the amino acid sequence, resulting in a truncated protein. The results of gene expression analysis indicated that the expression of <i>Pun1</i> in 'Nara Murasaki' was hardly detectable, while the transcripts of this gene were strongly expressed in a pungent cultivar. In a co-segregation test, the <i>pun1</i><sup>4</sup> genotype perfectly co-segregated with non-pungency in 103 F<sub>2</sub> population plants of a cross between 'Nara Murasaki' and a pungent cultivar. 'Nara Murasaki' and a DNA marker to distinguish the <i>pun1</i><sup>4</sup> allele will be informative for understanding the domestication process of sweet peppers.</p>

Journal

  • The Horticulture Journal

    The Horticulture Journal 86(1), 61-69, 2017

    The Japanese Society for Horticultural Science

Codes

  • NII Article ID (NAID)
    130005312842
  • NII NACSIS-CAT ID (NCID)
    AA12708073
  • Text Lang
    ENG
  • ISSN
    2189-0102
  • NDL Article ID
    027850834
  • NDL Call No.
    Z78-A456
  • Data Source
    NDL  J-STAGE 
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