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An abscisic acid-induced developmental checkpoint in plant germination: Study of its genetic and molecular control

English title An abscisic acid-induced developmental checkpoint in plant germination: Study of its genetic and molecular control
Applicant Lopez-Molina Luis
Number 120866
Funding scheme SNSF Professorships
Research institution Département de Biologie Végétale Faculté des Sciences Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Molecular Biology
Start/End 01.09.2008 - 31.08.2010
Approved amount 667'053.00
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All Disciplines (5)

Discipline
Molecular Biology
Genetics
Embryology, Developmental Biology
Cellular Biology, Cytology
Biochemistry

Keywords (15)

genetics; Arabidopsis; abscisic acid; gibberellic acid; ABI5; SnRK2; AUX1; auxin; active hormone metabolism; Abscisic acid (ABA); Gibberellins (GA); Hormone metabolism; Seed germination; Arabidopsis thaliana; RGL2

Lay Summary (English)

Lead
Lay summary
Seed germination, triggered upon seed imbibition by water, is a fragile phase in the life cycle of plants in which the embryo abandons a highly protective state in the mature seed and transits towards its autotrophic vegetative phase.The two phytohormones gibberellic acid (GA) and abscisic acid (ABA) exert an antagonistic influence on seed germination. GA, synthesized by the embryo upon imbibition, is an essential enabler of seed germination. In contrast, ABA, a stress hormone synthesized upon osmotic stress, can delay or prevent seed germination as well as confer osmotolerance to the embryo by maintaining embryogenesis gene products. There is strong evidence that GA and ABA pathways inhibit each other not only at the level of signal transmission but also at the level of active hormone metabolism. The nature of these last interactions is unknown.Osmotic stress and ABA induce the expression of ABI5, encoding a basic leucine-zipper transcription factor, which plays a central role in the execution of germination arrest and osmoprotection programs. However, ABA is also required for ABI5’s activity, likely involving ABI5 phosphorylation by SnRK2-type Ser/Thr kinases whose expression is positively controlled by ABA. The downstream gene programs withstanding germination arrest that are targeted by ABI5 are poorly understood.Here we propose two projects that address key issues regarding the control of seed germination by GA and ABA signaling pathways. We wish to 1) understand how GA and ABA pathways antagonize each other at the level of active hormone metabolism and 2) to study the nature of the downstream gene programs withstanding germination arrest that are targeted by ABI5 by examining the role of auxin.The first project utilizes transgenic plants where a SnRK2 kinase can be induced in a background of constitutive ABI5 expression. This allows artificial activation of ABA signaling in absence of osmotic stress or ABA application. Thus, we can explore changes in GA and ABA hormone metabolism under the direct control of ABI5. The second project arose after our identification of the long root suppressor mutation, which corresponds to a novel aux1 recessive allele. AUX1 encodes cellular membrane auxin influx carrier. The aux1 mutation suppresses the ABA- and ABI5-dependent hypersensitive responses observed in plants overexpressing ABI5. Thus, this second project might provide leads into downstream, auxin-dependent, germination processes in response to ABA.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
102890 An abscisic acid-induced developmental checkpoint in plant germination: Study of its genetic and molecular control 01.09.2004 SNSF Professorships
132591 The Role of RGL2 and the Seed Coat in Arabidopsis Seed Dormancy 01.01.2011 Project funding

Abstract

Seed germination, triggered upon seed imbibition by water, is a fragile phase in the life cycle of plants in which the embryo abandons a highly protective state in the mature seed and transits towards its autotrophic vegetative phase.The two phytohormones gibberellic acid (GA) and abscisic acid (ABA) exert an antagonistic influence on seed germination. GA, synthesized by the embryo upon imbibition, is an essential enabler of seed germination. In contrast, ABA, a stress hormone synthesized upon osmotic stress, can delay or prevent seed germination as well as confer osmotolerance to the embryo by maintaining embryogenesis gene products. There is strong evidence that GA and ABA pathways inhibit each other not only at the level of signal transmission but also at the level of active hormone metabolism. The nature of these last interactions is unknown.Osmotic stress and ABA induce the expression of ABI5, encoding a basic leucine-zipper transcription factor, which plays a central role in the execution of germination arrest and osmoprotection programs. However, ABA is also required for ABI5’s activity, likely involving ABI5 phosphorylation by SnRK2-type Ser/Thr kinases whose expression is positively controlled by ABA. The downstream gene programs withstanding germination arrest that are targeted by ABI5 are poorly understood.Here we propose two projects that address key issues regarding the control of seed germination by GA and ABA signaling pathways. We wish to 1) understand how GA and ABA pathways antagonize each other at the level of active hormone metabolism and 2) to study the nature of the downstream gene programs withstanding germination arrest that are targeted by ABI5 by examining the role of auxin.The first project utilizes transgenic plants where a SnRK2 kinase can be induced in a background of constitutive ABI5 expression. This allows artificial activation of ABA signaling in absence of osmotic stress or ABA application. Thus, we can explore changes in GA and ABA hormone metabolism under the direct control of ABI5. The second project arose after our identification of the long root suppressor mutation, which corresponds to a novel aux1 recessive allele. AUX1 encodes cellular membrane auxin influx carrier. The aux1 mutation suppresses the ABA- and ABI5-dependent hypersensitive responses observed in plants overexpressing ABI5. Thus, this second project might provide leads into downstream, auxin-dependent, germination processes in response to ABA.
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