Germination and storage reserve mobilization are regulated independently in Arabidopsis

• Published in: The Plant journal : for cell and molecular biology 2002-09, Vol.31 (5), p.639-647
• Main Authors: Pritchard, Sarah L., Charlton, Wayne L., Baker, Alison, Graham, Ian A.
• Format: Article
• Language: English
• Subjects: ABA; Abscisic Acid - pharmacology; Agronomy. Soil science and plant productions; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; beta‐oxidation; Biological and medical sciences; Economic plant physiology; Embryo development. Germination; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Developmental - drug effects; Gene Expression Regulation, Plant - drug effects; Germination - drug effects; Germination - genetics; Germination - physiology; Germination and dormancy; glyoxylate cycle; Glyoxylates - antagonists & inhibitors; Glyoxylates - metabolism; Growth and development; Lipid Metabolism; Mutation; Plant physiology and development; Seeds - drug effects; Seeds - growth & development; Seeds - metabolism; sucrose; Sucrose - metabolism; triacylglycerol; Triglycerides - metabolism
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.2002.01376.x

Summary The phytohormone abscisic acid (ABA) inhibits the germination of many seeds, including Arabidopsis, but the mechanism for this is not known. In cereals, ABA inhibits the expression of genes involved in storage reserve mobilization. We have found that in Arabidopsis ABA decreases transcription from the promoters of marker genes for β‐oxidation and the glyoxylate cycle, essential pathways for the conversion of storage lipid (triacylglycerol) into sucrose. Thirty per cent of stored lipid is broken down over 6 days following imbibition of ABA‐treated seed. Sucrose levels in ABA‐treated seeds, rather than decreasing as under normal growth conditions, actually double during the 3 days following imbibition. This sucrose is derived from triacylglycerol as demonstrated by two mutants disrupted in the conversion of triacylglycerol into sucrose, kat2 and icl1, which do not accumulate sucrose in the presence of ABA. We conclude that the ABA block on germination is not a consequence of inhibition of storage lipid mobilization. Two independent programmes appear to operate, one that is blocked by ABA, governing developmental growth resulting in germination; and a second that governs storage lipid mobilization which is largely ABA‐independent.