Skotomorphogenesis Seed germination Genes and enzymes Embryo and Seed development Plant life cycle.

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Presentation transcript:

Skotomorphogenesis Seed germination Genes and enzymes Embryo and Seed development Plant life cycle

Seed germination Dicot seed

Seed germination Monocot seed

Barley seed germination

Concept 1.Reception of environmental changes (daylength and temperature) 2. Signal transduction (photoreceptor signal transduction) 1.Differential gene regulation (GA biosynthesis genes) 2.Effect on plant development (seed germination)

Barley seed germination

Seed dormancy to germination Finkelstein et al. (2008) Annu Rev Plant Biol

Seed Dormancy Release and Germination Release in response to: stratification (low temperature w/moisture), changing light, dry storage After ripening (cool & dry storage) initiate decline in ABA, ethylene inhibits ABA signaling Stratification and light increase GA levels by inducing expression of GA biosynthetic genes and reducing expression of GA catabolic genes Finch-Savage & Leubner-Metzger, 2006

Mutation that blocks ABA biosynthesis results in premature seed germination in maize (and other species) Precocious germination (vivipary) in the ABA-deficient vivipary 14 (vp14) mutant of maize VP14 encodes NCED (9-cis-epoxycarotenoid dioxygenase), catalyzes rate limiting step in ABA biosynthesis ABA treatment of seed prevents germination ABA prevents premature seed germination by inducing and maintaining seed dormancy

Hartmann & Kester et al. Plant Propagation 2002 Three phases of germination: imbibition, lag and radicle emergence from the seed coat Primarily due to the matrix potential of dry seed (water potential gradient) after seed coat becomes water permeable Imbibition – period of rapid water uptake

Barley seed germination water 1 ppb GA 100 ppb GA

Induction of transcription factors after GA treatment

Barley seed germination

Gene regulation

Barley seed germination Gene regulation

GA induced  -amylase production GA reception at the plasma membrane GA induced  -amylase production Ca mediated signal transduction Signal transduction into the nucleus Regulation of transcription factors Differential expression of genes De novo synthesis of proteins (enzyme)  -amylase transport into the endosperm

Concept 1.Using chemical signals (phytohormones)(biosynthesis/catabolism) 2. Antagonists create check and balances (ABA and GA during seed development and germination) 1.Differential gene regulation (GA biosynthesis genes) 2.Effect on plant development (seed germination)

SKOTOMORPHOGENESIS Photomorphogenesis Skotomorphogenesis

SKOTOMORPHOGENESIS Skotomorphogenesis Light has an influence on seedling development Photomorphogenesis Skotomorphogenesis  Hypocotyl: long short  Apical hook: closed open  Cotyledons: closed expanded  Chloroplasts: proplastids fully developed  Photosynthesis: no yes