Field studies on the regulation of abscisic acid content and germinability during grain development of barley: molecular and chemical analysis of pre-harvest sprouting

• Published in: Journal of experimental botany Vol. 57; no. 10; pp. 2421 - 2434
• Main Authors: Chono, Makiko, Honda, Ichiro, Shinoda, Shoko, Kushiro, Tetsuo, Kamiya, Yuji, Nambara, Eiji, Kawakami, Naoto, Kaneko, Shigenobu, Watanabe, Yoshiaki
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01-01-2006; Oxford Publishing Limited (England)
• Subjects: 9-cis-epoxycarotenoid dioxygenase; ABA 8′-hydroxylase; abscisic acid; Abscisic Acid - metabolism; abscisic acid 8'-hydroxylase; after-ripening; Barley; biochemical pathways; Biological and medical sciences; Cell physiology; Complementary DNA; Cytochrome P-450 Enzyme System - genetics; Cytochrome P-450 Enzyme System - physiology; Dioxygenases; Dormancy; Embryos; environmental factors; enzymes; field experimentation; field-grown barley; Fundamental and applied biological sciences. Psychology; gene expression; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; genes; Genes, Plant; Germination; Germination - physiology; grain sprouting; Grains; Hordeum - genetics; Hordeum - growth & development; Hordeum - metabolism; Hordeum vulgare; Imbibition; Messenger RNA; Mixed Function Oxygenases - genetics; Mixed Function Oxygenases - physiology; Molecular and cellular biology; Molecular Sequence Data; nine-cis-epoxycarotenoid dioxygenase; Oxygenases - genetics; Oxygenases - physiology; Plant Proteins - metabolism; Pollination; pre-harvest sprouting; protein synthesis; Research Papers; Seed development; seed dormancy; Seeds - growth & development; Seeds - metabolism; Sequence Analysis, DNA; Signal transduction; Temperature; Time Factors; viability; Japan; germination; pre-harvest sprouting; ABA 8′-hydroxylase; nine-cis-epoxycarotenoid dioxygenase; dormancy; field-grown barley; abscisic acid; Monocotyledones; Hordeum vulgare; Enzyme; Growth; Germination; Hydroxylase; Imbibition; Biosynthesis; ABA 8'-hydroxylase; Dormancy; Complementary DNA; Gene; Gramineae; Angiospermae; Abscisic acid; Development; Spermatophyta; Catabolism; Oxidoreductases
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/erj215

To investigate whether the regulation of abscisic acid (ABA) content was related to germinability during grain development, two cDNAs for 9-cis-epoxycarotenoid dioxygenase (HvNCED1 and HvNCED2) and one cDNA for ABA 8'-hydroxylase (HvCYP707A1), which are enzymes thought to catalyse key regulatory steps in ABA biosynthesis and catabolism, respectively, were cloned from barley (Hordeum vulgare L.). Expression and ABA-quantification analysis in embryo revealed that HvNCED2 is responsible for a significant increase in ABA levels during the early to middle stages of grain development, and HvCYP707A1 is responsible for a rapid decrease in ABA level thereafter. The change in the embryonic ABA content of imbibing grains following dormancy release is likely to reflect changes in the expression patterns of HvNCEDs and HvCYP707A1. A major change between dormant and after-ripened grains occurred in HvCYP707A1; the increased expression of HvCYP707A1 in response to imbibition, followed by a rapid ABA decrease and a high germination percentage, was observed in the after-ripened grains, but not in the dormant grains. Under field conditions, HvNCED2 showed the same expression level and pattern during grain development in 2002, 2003, and 2004, indicating that HvNCED2 expression is regulated in a growth-dependent manner in the grains. By contrast, HvNCED1 and HvCYP707A1 showed a different expression pattern in each year, indicating that the expression of these genes is affected by environmental conditions during grain development. The varied expression levels of these genes during grain development and imbibition, which would have effects on the activity of ABA biosynthesis and catabolism, might be reflected, in part, in the germinability in field-grown barley.