Glucose-induced delay of seed germination in rice is mediated by the suppression of ABA catabolism rather than an enhancement of ABA biosynthesis.

Both glucose and ABA play crucial roles in the regulation of seed germination and post-germination development. In Arabidopsis thaliana, up-regulation of ABA biosynthesis is suggested as one of the possible mechanisms mediating the glucose-induced delay in seed germination. Since the endogenous ABA level is controlled by the equilibrium between ABA biosynthesis and catabolism, we investigated how this equilibrium is related to the regulation of seed germination by glucose in rice. When ABA biosynthesis was inhibited by nordihydroguaiaretic acid (NDGA), an inhibitor of the ABA anabolic enzyme 9-cis-epoxycarotenoid dioxygenase (NCED), rice seed germination showed no response. In contrast, inhibition of ABA catabolism by diniconazole significantly arrested seed germination, suggesting that the regulation of ABA catabolism plays a major role. Further experiments indicated that the expression of OsABA8ox3, a key gene in ABA catabolism and encoding ABA 8'-hydroxylase in rice, was significantly increased during the first 6 h of imbibition, which was consistent with the decline of ABA content in the imbibed seeds. Expression of OsABA8ox genes, especially OsABA8ox2 and OsABA8ox3, was sensitively suppressed in the presence of exogenously supplied glucose. In contrast, the expression profiles of OsNCED genes that control the limiting step of ABA biosynthesis showed no significant changes in response to low levels of glucose. Our results demonstrated that the glucose-induced delay of seed germination is a result of the suppression of ABA catabolism rather than any enhancement of ABA biosynthesis during rice seed germination.

[1]  C. Steber,et al.  Molecular aspects of seed dormancy. , 2008, Annual review of plant biology.

[2]  S. Iuchi,et al.  High Temperature-Induced Abscisic Acid Biosynthesis and Its Role in the Inhibition of Gibberellin Action in Arabidopsis Seeds12[C][W][OA] , 2008, Plant Physiology.

[3]  S. Smeekens,et al.  Interaction between sugar and abscisic acid signalling during early seedling development in Arabidopsis , 2008, Plant Molecular Biology.

[4]  Jing Liu,et al.  Dynamic analysis of ABA accumulation in relation to the rate of ABA catabolism in maize tissues under water deficit. , 2006, Journal of experimental botany.

[5]  Kun Yuan,et al.  Phytohormone signalling pathways interact with sugars during seed germination and seedling development. , 2006, Journal of experimental botany.

[6]  Y. Kamiya,et al.  CYP707A1 and CYP707A2, Which Encode Abscisic Acid 8′-Hydroxylases, Are Indispensable for Proper Control of Seed Dormancy and Germination in Arabidopsis1 , 2006, Plant Physiology.

[7]  J. B. Reid,et al.  Seed dormancy and ABA metabolism in Arabidopsis and barley: the role of ABA 8'-hydroxylase. , 2006, The Plant journal : for cell and molecular biology.

[8]  M. Bevan,et al.  Sugar and ABA response pathways and the control of gene expression. , 2006, Plant, cell & environment.

[9]  Caroline Smith,et al.  Establishing glucose- and ABA-regulated transcription networks in Arabidopsis by microarray analysis and promoter classification using a Relevance Vector Machine. , 2006, Genome research.

[10]  Y. Kamiya,et al.  Ethylene promotes submergence-induced expression of OsABA8ox1, a gene that encodes ABA 8'-hydroxylase in rice. , 2006, Plant & cell physiology.

[11]  K. Shinozaki,et al.  Chemical regulation of abscisic acid catabolism in plants by cytochrome P450 inhibitors. , 2005, Bioorganic & medicinal chemistry.

[12]  E. Nambara,et al.  Abscisic acid biosynthesis and catabolism. , 2005, Annual review of plant biology.

[13]  S. Gibson,et al.  Control of plant development and gene expression by sugar signaling. , 2005, Current opinion in plant biology.

[14]  Ashverya Laxmi,et al.  Global Transcription Profiling Reveals Multiple Sugar Signal Transduction Mechanisms in Arabidopsis , 2004, The Plant Cell Online.

[15]  Y. Kamiya,et al.  The Arabidopsis cytochrome P450 CYP707A encodes ABA 8′‐hydroxylases: key enzymes in ABA catabolism , 2004, The EMBO journal.

[16]  D. Ohta,et al.  Arabidopsis CYP707As Encode (+)-Abscisic Acid 8′-Hydroxylase, a Key Enzyme in the Oxidative Catabolism of Abscisic Acid1 , 2004, Plant Physiology.

[17]  S. Smeekens,et al.  Glucose delays seed germination in Arabidopsis thaliana , 2004, Planta.

[18]  S. Gibson Sugar and phytohormone response pathways: navigating a signalling network. , 2003, Journal of experimental botany.

[19]  J. Na,et al.  Mechanisms of Glucose Signaling during Germination of Arabidopsis1 , 2003, Plant Physiology.

[20]  S. Schwartz,et al.  Elucidation of the Indirect Pathway of Abscisic Acid Biosynthesis by Mutants, Genes, and Enzymes1 , 2003, Plant Physiology.

[21]  E. Nambara,et al.  A Unique Short-Chain Dehydrogenase/Reductase in Arabidopsis Glucose Signaling and Abscisic Acid Biosynthesis and Functions , 2002, The Plant Cell Online.

[22]  S. Gibson,et al.  Plant sugar-response pathways. Part of a complex regulatory web. , 2000, Plant physiology.

[23]  Sjef Smeekens,et al.  SUGAR-INDUCED SIGNAL TRANSDUCTION IN PLANTS. , 2000, Annual review of plant physiology and plant molecular biology.

[24]  S. Smeekens Sugar regulation of gene expression in plants. , 1998, Current opinion in plant biology.

[25]  A. Covarrubias,et al.  Abscisic acid inhibits germination of mature Arabidopsis seeds by limiting the availability of energy and nutrients , 1997, Planta.

[26]  P. León,et al.  Hexokinase as a sugar sensor in higher plants. , 1997, The Plant cell.

[27]  K. Koch CARBOHYDRATE-MODULATED GENE EXPRESSION IN PLANTS. , 1996, Annual review of plant physiology and plant molecular biology.

[28]  B. Loveys,et al.  A monoclonal antibody to (S)-abscisic acid: its characterisation and use in a radioimmunoassay for measuring abscisic acid in crude extracts of cereal and lupin leaves , 1988, Planta.

[29]  Robert Creeley,et al.  St. Martin's , 1971 .