Journal Article

Genes Encoding the Vacuolar Na<sup>+</sup>/H<sup>+</sup> Exchanger and Flower Coloration

Toshio Yamaguchi, Sachiko Fukada-Tanaka, Yoshishige Inagaki, Norio Saito, Keiko Yonekura-Sakakibara, Yoshikazu Tanaka, Takaaki Kusumi and Shigeru Iida

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 5, pages 451-461
Published in print May 2001 | ISSN: 0032-0781
Published online May 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce080
Genes Encoding the Vacuolar Na+/H+ Exchanger and Flower
Coloration

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  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Vacuolar pH plays an important role in flower coloration: an increase in the vacuolar pH causes blueing of flower color. In the Japanese morning glory (Ipomoea nil or Pharbitis nil), a shift from reddish-purple buds to blue open flowers correlates with an increase in the vacuolar pH. We describe details of the characterization of a mutant that carries a recessive mutation in the Purple (Pr) gene encoding a vacuolar Na+/H+ exchanger termed InNHX1. The genome of I. nil carries one copy of the Pr (or InNHX1) gene and its pseudogene, and it showed functional complementation to the yeast nhx1 mutation. The mutant of I. nil, called purple (pr), showed a partial increase in the vacuolar pH during flower-opening and its reddish-purple buds change into purple open flowers. The vacuolar pH in the purple open flowers of the mutant was significantly lower than that in the blue open flowers. The InNHX1 gene is most abundantly expressed in the petals at around 12 h before flower-opening, accompanying the increase in the vacuolar pH for the blue flower coloration. No such massive expression was observed in the petunia flowers. Since the NHX1 genes that promote the transport of Na+ into the vacuoles have been regarded to be involved in salt tolerance by accumulating Na+ in the vacuoles, we can add a new biological role for blue flower coloration in the Japanese morning glory by the vacuolar alkalization.

Keywords: Key words: Blue flower coloration — Japanese morning glory (Ipomoea nil) — NHX1 gene — Vacuolar Na+/H+ exchanger — Vacuolar pH.; Abbreviations: ANS, Anthocyanidin synthase; CHI, chalcone isomerase; CHS, chalcone synthase; DFR, dihydroflavonol 4-reductase; F3H, flavanone 3-hydroxylase; HBA, heavenly blue anthocyanin; Pr, Purple; pr-m, purple-mutable; Pr-r, Purple-revertant; PCR, polymerase chain reaction; RACE, rapid amplification of cDNA ends; RT, reverse transcription; UF3GT, UDP-glucose:flavonoid 3-O-glucosyl-transferase.; The nucleotide sequences reported in this paper have been submitted to DDBJ under accession numbers AB055062 (InNHX1 from Pr-r plant), AB055063 (InNHX1 pseudogene from Pr-r plant), AB054978 (InACT4), AB054979 (ItNHX1), AB051817 (PhNHX1), AB051819 (ThNHX1) and AB051818 (NcNHX1).

Journal Article.  7984 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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