タバコ落花および落果過程の離層におけるホウ素とホウ素–ペクチン複合体の存在量解析 Analysis of Boron and B-pectin Complex Content in the Abscission Zone during Floral and Fruit Abscission in Tobacco (<i>Nicotiana tabacum</i>)

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Abstract

本研究では,細胞接着性に重要であるペクチンとホウ素が,落花,落果過程の離層における細胞接着・構造維持にどのような働きを持つかについて調査した.本研究の材料には,タバコ(<i>Nicotiana tabacum</i>)の品種 Bright-Yellow 2 の花柄を用いて,離層におけるホウ素量およびペクチン–ホウ素架橋形成率を測定した.また,花柄および離層におけるペクチン–ホウ素架橋形成に重要である <i>NtGUT1</i> とホウ素輸送隊である <i>NtNIP3;1</i> の発現解析を行った.全ホウ素量は,つぼみ,果実のいずれにおいても花柄より離層に多く存在していたが,水溶性ホウ素および架橋に関連するホウ素量ともに違いはなかった.ペクチン–ホウ素架橋形成率は,ステージの進行に伴い上昇傾向にあるが,つぼみ,果実のいずれにおいても花柄と離層で同程度であった.<i>NtGUT1</i> と <i>NtNIP3;1</i> の発現解析では,開花直前の花の離層において <i>NtGUT1</i> の発現量が上昇していた.しかし受粉阻止処理をした場合,人工授粉処理をした花の離層でホウ素量および発現に変化はなかった.これらの結果から,ホウ素が離層に多く存在し,また,ステージの進行に伴った増加をすることが示された.しかし,これらは受粉や器官脱離とは大きな関係はないと考えられる.<br>

After fruit development has been triggered by pollination, the abscission zone (AZ) in the pedicel strengthens its adhesion to retain the fruit. In tobacco, unpollinated flowers are shed from the AZ, while enlargement of the same tissue occurs in pollinated flowers. The abscission rate depends on effective pollination. In this study, we focused on pectin and boron (B) distribution and their functions in the AZ. B is an essential micronutrient that forms cross-links in pectin, which are important for organ differentiation and maturation. B content and the formation rate of the borate-ester cross-linked rhamnogalacturonan II dimer (dRG-II-B) were measured in tobacco. Expression of <i>NtGUT1</i>, which is important for the formation of dRG-II-B, and the B transporter <i>NtNIP3;1</i> were analyzed in the peduncle and AZ. To determine B content and dRG-II-B formation rate, the following samples were collected: bud peduncle, bud AZ, fruit peduncle, fruit AZ, and flower AZs, which were treated to prevent pollination or were artificially pollinated. Samples treated in HNO<sub>3</sub> were assayed for total B content with ICP-MS. <i>Endo</i>-polygalacturonase (EPG)-treated alcohol-insoluble residues were assayed for formation rates of dRG-II-B with HPLC. Although there was more total B in fruit AZs than in branches, no differences in total B, water-soluble B, and B relevant to cross-linking with RG-II were found between buds and fruits. The formation rates of dRG-II-B were also the same in peduncles and AZs in both buds and fruits. These have the same characteristics of variation with or without pollination. Expression of both <i>NtGUT1</i> and <i>NtNIP3;1</i> was highest in AZs of flowers before opening, however, expression of <i>NtGUT1</i> in flower AZs without pollination was not significantly different from after artificial pollination. These results suggest that the presence of relatively large amounts of B and pectin is important in structural enhancement of AZs after anthesis, but is not related to abscission with or without pollination.<br>

Journal

  • Journal of the Japanese Society for Horticultural Science

    Journal of the Japanese Society for Horticultural Science 82(1), 83-90, 2013

    THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE

Codes

  • NII Article ID (NAID)
    130004510770
  • NII NACSIS-CAT ID (NCID)
    AA12177046
  • Text Lang
    ENG
  • ISSN
    1882-3351
  • NDL Article ID
    024212725
  • NDL Call No.
    Z78-A456
  • Data Source
    NDL  J-STAGE 
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