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