EMBRYONIC PATTERNING IN Arabidopsis thaliana Flashcards
Introduction: Evolution of Plant Embryos (8)
- Origin of Plants
- Cambrian Explosion
- Ancestral Plant Characteristics
- Sporophyte Development
- Embryo Development
- Seed Plants and Double Fertilization
- Genetic Control
- Polarity and Plant Development
Origin of Plants: Plants originated less than 500 million years ago, evolving from multicellular ____ that, in partnership with symbiotic fungi, began to colonize land.
_____: This period already saw the establishment of most animal phyla, indicating that plants emerged significantly later in the evolutionary timeline.
Ancestral Plant Characteristics:
Early plant ancestors were multicellular _____, which means they did not produce embryos.
Meiosis followed by fertilization produced haploid spores.
Modern plant life cycles are more complex, featuring a multicellular diploid phase known as the ____.
green algae
Cambrian Explosion
haplonts
sporophyte
Sporophyte Development:
Initial sporophytes were small, short-lived, and reliant on the gametophyte (haploid generation).
In contrast to primitive plants like ____ and ____where the gametophyte is dominant, in most plants, the sporophyte phase is predominant.
Embryo Development:
All young plant sporophytes (embryos) develop closely associated with the parental generation, either within a ______ or encased within a seed.
Seed Plants and Double Fertilization:
In seed plants, a double fertilization event produces both the ___ and ____.
Seed development involves cooperation between five genetically distinct entities: the maternal and paternal sporophyte, the male and female gametophytes, and the endosperm.
liverworts and mosses
free-living gametophyte
embryo and the triploid endosperm
Genetic Control:
Many fertilization-related functions are regulated by the _____.
The development of the endosperm is influenced by an imprinting mechanism established by the female gametophyte.
Embryonic patterning appears largely autonomous, often suggested by studies involving mutants of Arabidopsis that can produce embryos from usually non-embryonic cells.
Polarity and Plant Development:
Plant development is non-determinate, with continuous production of new growth axes and lateral organs.
Defining embryogenesis in non-seed plants is challenging due to the absence of a _____ interrupting sporophyte growth.
haploid female gametophyte
seed dormancy phase
Early Cell-Fate Decisions in Arabidopsis Embryogenesis
____ Critical in regulating basal cell development. Mutations in YDA can disrupt suspensor formation, altering normal embryonic patterns.
_____ a key plant hormone, plays a crucial role in establishing cell polarity and axis formation. ____ regulate auxin transport, crucial for proper embryo development.
YODA (YDA) gene
Auxin,
PIN-formed (PIN) proteins
_____ like those of the WOX family display patterns that correspond closely to anatomical cell division patterns.
_____Cytoplasmic channels that connect cells, facilitating communication and molecule transfer, essential for regulating gene expression.
homeodomain genes
plasmodesmata
Mutations in _____ to abnormal suspensor development. Without proper function, the zygote fails to elongate properly and divides abnormally, resulting in defective embryonic and suspensor development.
YDA
YDA Function: Active in the zygote to promote normal elongation. After the zygote divides, YDA activity is downregulated in the apical cell, allowing it to develop into _____.
In contrast, YDA remains active in the basal cell, promoting its elongation and division along a specific plane to form the suspensor.
embryonic structures
____ key plant hormone critical for embryonic development, influencing cell division, elongation, and differentiation.
Auxin
_____ The directional movement of auxin, mediated by _____, establishes the primary axis of the embryo and influences subsequent developmental patterns.
_____ regulate auxin transport. Their localization within cells determines the direction of auxin flow, influencing the developmental axis and polarity of the embryo
Auxin Flux
PIN proteins (PIN-formed)
PIN proteins
____ The first recognizable sign of epidermal development, marked by specific gene expression patterns, such as those for the PROTODERMAL FACTOR (PDF) and MERISTEM LAYER1 (AtML1) genes.
The initiation of cotyledons, the first leaves of the plant, is closely linked to the development of the SAM. Cotyledons form at the boundary of the central and peripheral domains of the SAM.
Protoderm formation
cotyledons
The apical region of the Arabidopsis embryo develops into the _____, which is responsible for the production of all aerial parts of the plant.
shoot apical meristem (SAM),
