Plants Flashcards
What is the difference between embryogenesis in animal and plants
Animals all tissues and organs are formed in embryogenesis - as organism grows tissues and organts
* Plant- Seed leaves- only base body plan formed- and primitive root- adult tissues and organs form post-embryonically from meristems
What is the shoot apical meristem?
Plant stem cells population come from this- plant tissues and organs made from this - so it is key that the population is maintained
What are the key features of plant growth and development?
• MOst development is post embryonic
• Cells are fixed (cell wall) and do not migrate
• Cell position determines cells identity (not cell lineage)
• Cells divide, then expand, then differentiate
• Self organising meristems contain stem cells
• Stem cells allow indeterminate growth
How care cell organised into complex 3D structures?
• all cells derive from shoot or root meristems
• Iterative nature of development
• Morphogens
• Cell to cell signalling
• Fundamental pattern establishment
What are fractals?
Fundamentals properties of how plants grow- they keep branching
Describe shoot development in plants
Shoot development in plants:
All above ground tissues and organs derive from the shoot apical meristem (SAM)
SAM contains pluripotent stem cells
These stem cells give rise to PHYTOMERS
Phytomer = leaf (Organ), axillary bud, and internode
Shot growth is the iterative (repeated) formation of phytomers
what is the shoot apical meristem?
Begin as a bulge stem cells population in centre never involved in organogenesis
What is Phyllotaxis?
The pattern of organ emergence
What is the Fibonacci spiral?
Spirals in opposite direction.
DIVERGENCE ANGLE OF 137.5 degrees
What specifies cell identity and fate?
Cell position not cell lineage
What regulates lateral root emergence?
Phytohormone auxin
What is the shoot apical meristem (SAM)
Arabidopsis Thaliana: the principle model organism for plant development
Small,easy to grow, with short life cycle (6-8 weeks)
Fully sequenced genome 135mb on 5 chromosomes
Large selection of online research resources
Easy to transform
Mutants available in every gene. Used extensively as a model organism for plant development
The arabidopsis SAM produced leaves during vegetative growth and flowers during productive growth
What is the phytomer concept?
Plant bodies are assembled from developmental subunits called phytomers which are produced by SAM
What are the three layers in SAM?
Three layers in SAM
Epiderminal tissue
Supeipdermal/ ground tissue
Vasculature tissue and stem pith
What is Knotted1?
Like homeobox genes (KNOX genes)- encoded homeodomain TFs - homeodomain is highly conserved between animals, plants and fungi.
KNOX proteins ave an extended tale homeodomain (three amino acid loop extension (Tale)
Bind DNA via homeodomain and activate or repress transcription of target gene via MEINOX domain
What is the role of KNOX genes in shoot meristems?
The KNOX gene shoot meristemless (STM)
* STM is expressed in non-organogenic cells of shoot meristems
* STM promotes. Pluripotency in cells in which it is expressed
* Switched of in leaf founder cells, primordia and mature leaves
* Down-regulation in leaf primordia allows cells to enter differentiation pathways
What is the role of STM transcription factor in SAM development and function?
• STM is required for formation of SAM during embryogenesis
• STM required for maintained (continued self-renewal_ of the SAM during post embryonic adult growth
• STM is sufficient to activate de novo shoot meristems formation
