Arabidopsis ABA INSENSITIVE4 Regulates Lipid Mobilization in the Embryo and Reveals Repression of Seed Germination by the Endosperm[W]

Regulation of seed germination requires coordinate action by the embryo and surrounding endosperm. We used Arabidopsis thaliana to establish the relative roles of embryo and endosperm in the control of seed germination and seedling establishment. We previously showed that endospermic oil reserves are used postgerminatively via gluconeogenesis to fuel seedling establishment and that lipid breakdown is repressed by abscisic acid (ABA) in embryo but not endosperm tissues. Here, we use RNA amplification to describe the transcriptome of the endosperm and compare the hormone responses of endosperm and embryo tissues. We show that the endosperm responds to both ABA and gibberellin but that ABA in particular regulates nuclear but not plastid-encoded photosynthetic gene expression in the embryo. We also show that ABA INSENSITIVE4 (ABI4) expression is confined to the embryo, accounts for the major differences in embryo response to ABA, and defines a role for ABI4 as a repressor of lipid breakdown. Furthermore, ABI5 expression in the endosperm defines a second region of altered ABA signaling in the micropylar endosperm cap. Finally, embryo and endosperm ABA signaling mutants demonstrate the spatial specificity of ABA action in seed germination. We conclude that the single cell endosperm layer plays an active role in the regulation of seed germination in Arabidopsis.

[1]  Ayuko Kuwahara,et al.  Gibberellin Biosynthesis and Response during Arabidopsis Seed Germination Online version contains Web-only data. Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.011650. , 2003, The Plant Cell Online.

[2]  F. Berger.  Endosperm: the crossroad of seed development. , 2003, Current opinion in plant biology.

[3]  F. Berger.  Endosperm development. , 1999, Current opinion in plant biology.

[4]  R. Tibshirani,et al.  Significance analysis of microarrays applied to the ionizing radiation response , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[5]  K. Becker,et al.  Analysis of microarray data using Z score transformation. , 2003, The Journal of molecular diagnostics : JMD.

[6]  M. Moloney,et al.  The seed-specific transactivator, ABI3, induces oleosin gene expression. , 2000, Plant science : an international journal of experimental plant biology.

[7]  T. Lynch,et al.  Regulation and function of the Arabidopsis ABA-insensitive4 gene in seed and abscisic acid response signaling networks. , 2000, Plant physiology.

[8]  D. Weigel,et al.  GAMYB-like genes, flowering, and gibberellin signaling in Arabidopsis. , 2001, Plant physiology.

[9]  J. Micol,et al.  Genetic analysis of salt-tolerant mutants in Arabidopsis thaliana. , 2000, Genetics.

[10]  J. Vandekerckhove,et al.  The Effect of α-Amanitin on the Arabidopsis Seed Proteome Highlights the Distinct Roles of Stored and Neosynthesized mRNAs during Germination1 , 2004, Plant Physiology.

[11]  P. Toorop,et al.  The second step of the biphasic endosperm cap weakening that mediates tomato (Lycopersicon esculentum) seed germination is under control of ABA. , 2000, Journal of experimental botany.

[12]  P. León,et al.  Analysis of Arabidopsis glucose insensitive mutants, gin5 and gin6, reveals a central role of the plant hormone ABA in the regulation of plant vegetative development by sugar. , 2000, Genes & development.

[13]  L. Lepiniec,et al.  The Arabidopsis AtEPR1 extensin-like gene is specifically expressed in endosperm during seed germination. , 2000, The Plant journal : for cell and molecular biology.

[14]  Falk,et al.  Metabolic bypass of the tricarboxylic acid cycle during lipid mobilization in germinating oilseeds. Regulation Of nad+-dependent isocitrate dehydrogenase versus fumarase , 1998, Plant physiology.

[15]  R. Kalla,et al.  Gibberellin-regulated expression of a myb gene in barley aleurone cells: evidence for Myb transactivation of a high-pI alpha-amylase gene promoter. , 1995, The Plant cell.

[16]  Z. Pei,et al.  NADPH oxidase AtrbohD and AtrbohF genes function in ROS‐dependent ABA signaling in Arabidopsis , 2003, The EMBO journal.

[17]  S. Rhee,et al.  MAPMAN: a user-driven tool to display genomics data sets onto diagrams of metabolic pathways and other biological processes. , 2004, The Plant journal : for cell and molecular biology.

[18]  T. Lynch,et al.  The Arabidopsis Abscisic Acid Response Gene ABI5 Encodes a Basic Leucine Zipper Transcription Factor , 2000, Plant Cell.

[19]  I. Graham,et al.  Storage reserve mobilization in germinating oilseeds: Arabidopsis as a model system. , 2005, Biochemical Society transactions.

[20]  S. Gibson,et al.  The Arabidopsis sugar-insensitive mutants sis4 and sis5 are defective in abscisic acid synthesis and response. , 2000, The Plant journal : for cell and molecular biology.

[21]  T. Lynch,et al.  Regulatory Networks in Seeds Integrating Developmental, Abscisic Acid, Sugar, and Light Signaling1 , 2003, Plant Physiology.

[22]  F. Parcy,et al.  Regulation of gene expression programs during Arabidopsis seed development: roles of the ABI3 locus and of endogenous abscisic acid. , 1994, The Plant cell.

[23]  I. Graham,et al.  Plastid redox state and sugars: interactive regulators of nuclear-encoded photosynthetic gene expression. , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[24]  Stefan R. Henz,et al.  A gene expression map of Arabidopsis thaliana development , 2005, Nature Genetics.

[25]  P. Weisbeek,et al.  The Arabidopsis SUCROSE UNCOUPLED-6 gene is identical to ABSCISIC ACID INSENSITIVE-4: involvement of abscisic acid in sugar responses. , 2000, The Plant journal : for cell and molecular biology.

[26]  Steven Penfield,et al.  Reserve Mobilization in the Arabidopsis Endosperm Fuels Hypocotyl Elongation in the Dark, Is Independent of Abscisic Acid, and Requires PHOSPHOENOLPYRUVATE CARBOXYKINASE1 , 2004, The Plant Cell Online.

[27]  J. Bewley.  Breaking down the walls — a role for endo-β-mannanase in release from seed dormancy? , 1997 .

[28]  L. Herrera-Estrella,et al.  Sugar and ABA responsiveness of a minimal RBCS light-responsive unit is mediated by direct binding of ABI4. , 2005, The Plant journal : for cell and molecular biology.

[29]  Yuji Kamiya,et al.  Genome-wide profiling of stored mRNA in Arabidopsis thaliana seed germination: epigenetic and genetic regulation of transcription in seed. , 2005, The Plant journal : for cell and molecular biology.

[30]  I. Graham,et al.  Co-ordinate regulation of genes involved in storage lipid mobilization in Arabidopsis thaliana. , 2001, Biochemical Society transactions.

[31]  Yuji Kamiya,et al.  Activation of Gibberellin Biosynthesis and Response Pathways by Low Temperature during Imbibition of Arabidopsis thaliana Seeds On-line version contains Web-only data. , 2004, The Plant Cell Online.

[32]  K. Thompson,et al.  Seeds: Physiology of Development and Germination , 1986 .

[33]  M. Bevan,et al.  GUS fusions: beta‐glucuronidase as a sensitive and versatile gene fusion marker in higher plants. , 1987, The EMBO journal.

[34]  M. Koornneef,et al.  Seed dormancy and germination. , 2002, Current opinion in plant biology.

[35]  C. M. Karssen,et al.  Gibberellin-induced hydrolysis of endosperm cell walls in gibberellin-deficient tomato seeds prior to radicle protrusion , 1988, Planta.

[36]  H. Goodman,et al.  The Arabidopsis Abscisic Acid Response Locus ABI4 Encodes an APETALA2 Domain Protein , 1998, Plant Cell.

[37]  R. Finkelstein.  Mutations at two new Arabidopsis ABA response loci are similar to the abi3 mutations , 1994 .

[38]  P. McCourt,et al.  A mutant of Arabidopsis which is defective in seed development and storage protein accumulation is a new abi3 allele , 1992 .

[39]  S. Yamaguchi,et al.  Distinct cell-specific expression patterns of early and late gibberellin biosynthetic genes during Arabidopsis seed germination. , 2002, The Plant journal : for cell and molecular biology.

[40]  P. Benfey,et al.  High-Throughput RNA Isolation Technologies. New Tools for High-Resolution Gene Expression Profiling in Plant Systems1 , 2005, Plant Physiology.

[41]  N. Chua,et al.  Sucrose control of phytochrome A signaling in Arabidopsis. , 1997, The Plant cell.

[42]  Joachim Selbig,et al.  Extension of the Visualization Tool MapMan to Allow Statistical Analysis of Arrays, Display of Coresponding Genes, and Comparison with Known Responses1 , 2005, Plant Physiology.

[43]  H. Goodman,et al.  Isolation of the Arabidopsis ABI3 gene by positional cloning. , 1992, The Plant cell.

[44]  E. Nambara,et al.  Functional analysis of Arabidopsis NCED6 and NCED9 genes indicates that ABA synthesized in the endosperm is involved in the induction of seed dormancy. , 2006, The Plant journal : for cell and molecular biology.

[45]  F. Corke,et al.  Impaired sucrose-induction mutants reveal the modulation of sugar-induced starch biosynthetic gene expression by abscisic acid signalling. , 2001, The Plant journal : for cell and molecular biology.

[46]  Po-Pu Liu,et al.  Large-scale screening of Arabidopsis enhancer-trap lines for seed germination-associated genes. , 2005, The Plant journal : for cell and molecular biology.

[47]  I. Graham,et al.  Germination and storage reserve mobilization are regulated independently in Arabidopsis. , 2002, The Plant journal : for cell and molecular biology.

[48]  C. M. Karssen,et al.  The isolation of abscisic acid (ABA) deficient mutants by selection of induced revertants in non-germinating gibberellin sensitive lines of Arabidopsis thaliana (L.) heynh. , 1982, Theoretical and Applied Genetics.