L37 Plant_Development

Page 1: Overview of Plant Development

• Unique characteristics of plant development

  • The development of plants is distinctive compared to animals.

  • Determinants of plant form focus on mechanisms rather than fixed structures.

Page 2: Indeterminate Growth

• Plant growth and development are intermediate

  • not fixed in lifespan or size.

  • This contrasts with animal growth, which is usually determinate (fixed in scale and time).

Page 3: Plasticity and Modularity in Growth

• Unique features of plant development:

  • Plasticity: Growth is adaptable, allowing plants to change development in response to environmental cues.

  • Modular Growth: Development features repetitive patterns.

  • Morphogenesis (plant form) arises within cell walls and depends entirely on cell division

Page 4: Totipotency and Developmental Plasticity

• Indeterminate and Plastic Growth

• Totipotency: The expression of developmental plasticity.

  • Enables clonal propagation allowing a single plant to reproduce via vegetative means.

  • Example: Coleus plant shows vascular differentiation after needle puncture.

• Plasticity: able to adapt/alter development ‘on the fly‘ (no fixed blueprint for development)

  

Page 5: Development Without a Blueprint

• laws are guidelines that apply to developmental modules

Page 6: Insight into Developmental Guidelines

• Detailed examination of Arabidopsis embryo development to illustrate guidelines.

Page 7: Zygotic vs. Somatic Development

• Zygotic Embryogenesis:

  

• Somatic embryogenesis

  

• Somatic Development: Involves processes like direct and indirect somatic embryogenesis.

Page 8: Cell Division Patterns in Embryogenesis

• Initial cell divisions provide structure and 'bulk':

  • Zygotic Stages:

    • 1-cell to Octant stage embryo.

  • Importance of auxin patterns and crucial gene interactions (e.g., WOX, YDA).

Page 9: Cell Layering in Embryogenesis

• 5th division (16-cell stage) and beyond

  • results in cell layers, eg protoderm forming epidermis

Page 10: Stages of Embryogenesis

• Heart Stage:

  • Exhibits multiple cell layers that aid in the differentiation of tissues.

  • Key genes involved include DRN, WUS, CUC influencing the axillary development of shoot and root apical meristems.

  • Two bulging cotyledons (forming the heart shape).

  • A clear apical-basal axis (top-to-bottom organization)

• The shoot apical meristem (SAM) and root apical meristem (RAM) start to become organized

Page 11: The Torpedo Stage

• becomes elongated by stretching along its apical-basal axis

• Cotyledons (seed leaves) continue to grow and spread outward.

• Shoot Apical Meristem (SAM) and Root Apical Meristem (RAM) are fully established and positioned:

  • SAM is between the cotyledons.

  • RAM is at the opposite pole (bottom of the torpedo)

• Mature phase

  • looks like a tiny formed plant

Page 12: Implications of Pattern Disruption

• Single genetic lesions (eg. transcriptional regulators) eliminate entire cell groupings, not just tissues (N.B. gene expression is normally cell-type specific)

• Disruption in patterns indicates spatial guidelines during development.

  • Genetic lesions can affect not just tissue types but entire cell groupings, emphasising the importance of positional interactions.

• implies positional (spatial interactions) are important.

Page 13: Arabidopsis Mutants and Positional Interactions

• fass mutant (fassiculated): Loss of positional interactions leads to disorganised cell wall arrangements.

  • In arabidopsis, the fass mutant demonstrates how crucial positional interactions are for maintaining proper cell organisation, as the disorganisation results in compromised structural integrity and functionality of the plant.

Page 14: Cell Division Control

• knolle mutant (club):

  • Disruption in cell division control leads to irregular and oversized cells.

  • Importance of structural proteins for proper cell division function.

  • in arabidopsis thaliana has shown that these mutations can significantly affect overall plant morphology and development.

  • knolle is a structural protein needed to form the cell division plate

Page 15: Complexity from Simple Rules

• Fundamental rules of cell association can lead to complex developmental structures.

  • Interaction strategies dictate tissue formation through the positioning of colored cell types (red and white).

Page 16: Summary and Key Concepts

• plant development is intermediate and plastic

• plant morphogenesis arises entirely from cell division and cell lineage

• Simple rules of association provide guidelines for development