Bio 131 1st LE

Plant Developmental Biology

Development

The process that builds an organism.

Ameboid tapetum

protoplasts lacking cell walls enlarge and fuse with one another and move into locule to surround developing pollen grains

Secretory tapetum

protoplast is stationary after cell walls lyse. Protoplasts break down and are resorbed

L1

Epidermis, stomium

L2

Hypodermis, Endothecium, Middle layer, Tapetum

L3

Vascular bundle, Connective tissue

Basic

→ both secondary parietal cell layers divide to yield 2 middle layers

Dicotyledonous

• → only outer secondary parietal cell layer divides to yield endothecium and single middle layer

Monocotyledonous

• → only inner secondary parietal cell layer divides to yield tapetum and single middle layer

Reduced

• → secondary parietal cells do not divide and develop into endothecium and tapetum respectively

2 phases of stamen dev

• Phase I → sporogenic cells engage in microsporogenesis while nonsporogenic cells form epidermis, tapetum, etc…

  • Growth, histodifferentiation, meiosis 

• Phase II → anther enlarges and filament elongates, pollen grains form, dehisce, and released 

  • Tissue degeneration, dehiscence, pollen release

Differential gene expression

The expression of different genes by cells with the same genome.

Transcriptional level

Regulation of gene expression during the formation of the primary transcript.

Processing level

Regulation of gene expression at the stage of splicing.

Plastic Development

The ability of development to be adjusted according to prevailing environmental conditions.

Totipotency

The ability of a cell to become any organ or cell and give rise to a complete plant.

Post-Embryonic

The difference between animal development, which is mostly embryogenesis, and plant development, which involves post-embryonic development after seed germination.

Anticlinal division

Cell division with cell plates perpendicular to the surface, leading to the expansion of the surface.

Periclinal division

Cell division with cell plates parallel to the surface, leading to protrusion from the surface.

Control of Cell Fate

The regulation of cell fate through intercellular and extracellular information that changes gene activity.

Autotrophy

The difference between plants and animals;

plants assimilate energy and nutrients separately,

animals obtain energy and nutrients from food.

Model organism

A short generation time, characterized genome, and similarity to a member of a particular group, making it ideal for studying plant development.

Differentiation

The process in which generalized cells specialize into morphologically and physiologically different cells.

Dedifferentiation

The reversal of cell development in plants, resulting in the loss of differentiation and a more generalized structure.

Redifferentiation

The differentiation that occurs after dedifferentiation, forming the same mature cell type or a different one.

Pattern Formation

The process by which organisms create spatially-ordered and reproducible structures.

Organized cell growth and cell architecture

The preferential elongation of cells along certain axes and the orientation of cell growth in the plane perpendicular to the orientation of cellulose microfibrils in the cell wall.

External cues

External signals that influence the initial arrangement of cells and create a spatial pattern.

Lateral inhibition

Interactions between neighboring cells that prevent both from adopting the same fate.

Programmed cell death

The selective death of some cells to sculpt tissue.

Plant Cell Division

The process of cytokinesis in flowering plants, involving the construction of a new cell wall from the inside out and the use of microtubule-dependent mechanisms.

Mitosis

The process of cell division in which a cell divides into two identical daughter cells.

Actin

A protein that plays a role in cell movement and division.

PPB

Preprophase band, a ring of actin filaments that forms around the nucleus of a plant cell before mitosis.

Mitotic spindle

A structure made of microtubules that helps separate the chromosomes during mitosis.

Phragmoplast

A structure that forms during plant cell division and guides the vesicles containing cell wall material to the division plane.

Cortical division zone (CDZ)

The division plane in plant cells that is outlined by the PPB in response to selection cues.

Cell plate

A structure that forms during plant cell division and eventually becomes the new cell wall.

Cell Wall

A dynamic structure that provides support and protection to plant cells.

Cellulose microfibrils

Long, linear chains of cellulose molecules that make up the primary cell wall.

Hemicelluloses

Polysaccharides that help determine the extensibility and stiffness of the cell wall.

Pectins

Polysaccharides that regulate wall properties by controlling wall porosity and hydration.

Structural proteins

Proteins that contribute to the strength and integrity of the cell wall.

Auxin

A plant hormone that promotes cell elongation and regulates cell wall properties.

Cellulose synthases

Enzymes responsible for synthesizing cellulose microfibrils.

Autonomous mechanism

A mechanism in which cellulose synthase complexes interact with trails left by other complexes to maintain aligned trajectories.

Microtubule guidance system

A mechanism in which microtubules guide cellulose synthase complexes to control microfibril organization.

Xyloglucans

Hemicelluloses found mainly in primary cell walls that participate in cell wall extension during cell elongation.

Homogalacturonan

A type of pectin that influences wall extensibility by influencing the alignment of cellulose microfibrils.

Expansins

Proteins that loosen the cell wall and enhance wall expansion.

Arabinogalactan proteins (AGPs)

Proteins that play a role in plant protection and overall plant development.

Auxin signaling

The process by which auxin regulates gene expression and cell wall-related processes.

TIR1

A nuclear auxin receptor that binds to auxin and targets proteins for degradation.

Auxin/Indole-3-Acetic Acid (AUX/IAA)

Proteins that repress auxin-mediated transcription in the absence of auxin.

Auxin Response Factors (ARFs)

Proteins that interact with AUX/IAAs to regulate gene transcription in the presence of auxin.

Apoplast

The space outside the plasma membrane in plant cells.

Plasmodesmata

Channels that connect adjacent plant cells and allow for intercellular communication and transport.

Alternation of Generation

The life cycle of flowering plants, changing from sporophytes to gametophytes and vice versa.

Sporophyte

The diploid generation of an angiosperm that produces spores.

Gametophyte

The haploid generation of an angiosperm that produces gametes.

Megasporogenesis

The process of megaspore formation in the ovules of angiosperms.

Megagametogenesis

The process of female gamete formation in the embryo sac of angiosperms.

Microsporogenesis

The process of microspore formation in the anthers of angiosperms.

Microgametogenesis

The process of male gamete formation in pollen grains of angiosperms.

Microsporocyte

A diploid cell that undergoes meiosis to produce four haploid microspores.

Pollen Grain

A mature structure containing two cells, the generative cell and the tube cell, that is responsible for delivering sperm to the embryo sac.

Pollen Tube

An extension of the cytoplasm of the tube cell that grows through the style and towards the micropyle to deliver sperm nuclei.

Sperm Nuclei

The two nuclei produced by the generative cell through mitosis, which are responsible for fertilizing the egg cell and central cell in the embryo sac.

Stamen

The male reproductive organ of a flower, consisting of an anther and a filament.

Anther

The part of the stamen where microsporogenesis occurs, consisting of lobes with microsporangia that produce pollen grains.

Tapetum

The innermost layer of cells in the anther that surrounds the developing microspores and provides nutrients for their growth.

Dehiscence

The process of anther opening to release pollen grains.

Epidermis

The outermost layer of cells in the anther that protects the internal tissues.

Endothecium

The layer of radially elongated cells in the anther that develops fibrous thickenings to aid in anther dehiscence.

Middle Layer

The layer between the endothecium and the tapetum that may or may not be present in mature anthers.

Circular Cell Cluster

A group of cells found in the tapetum that accumulates calcium oxalate crystals and undergoes apoptosis before anther dehiscence.

Floral Meristem

The region of undifferentiated cells in a flower bud that gives rise to all the structures of the flower, including the anther.

Archesporial cells

The cells derived from the periclinal division of the hypodermis in the anther that give rise to microsporocytes.

Pollenkitt

Compounds produced by the tapetum that impart stickiness to the pollen grains and aid in their adhesion to the stigma.

Tryphine

A mixture of hydrophilic substances derived from tapetal cell debris that encrusts the pollen wall and aids in the adhesion of pollen grains to the stigma.

Sporogenic Cells

Cells in the anther that undergo meiosis to form microsporocytes.

QRT Genes

Genes required for proper pollen separation, with mutations resulting in fused pollen grains released as tetrads.

Microgametogenesis

The process of microspore development into microgametophytes, including the formation of the generative and vegetative cells.

Vegetative Cell

The larger cell formed during pollen mitosis I, which contains the nucleus and cytoplasm responsible for pollen tube growth.

Generative Cell

The smaller cell formed during pollen mitosis I, which lacks mitochondria and chloroplasts and is responsible for dividing to produce sperm nuclei.

Asymmetrical cell division

A type of cell division that results in daughter cells with different sizes or fates.

Microtubules

Cylindrical structures made of protein tubulin that play a role in cell division and intracellular transport.

Pollen wall

The protective outer layer of the pollen grain.

Exine

The outer layer of the pollen wall, composed of sporopollenin and resistant to decay.

Intine

The inner layer of the pollen wall, composed of pectocellulosic materials.

Hormonal regulation of pollen development

The control of pollen development by plant hormones such as gibberellins, jasmonic acid, and auxin.

Male sterility

The inability of a plant to produce functional pollen, resulting in the inability to fertilize ovules.

Ovule

The structure in the ovary of a flower that contains the female gametophyte and develops into a seed after fertilization.

Carpel

The female reproductive organ of a flower, consisting of the ovary, style, and stigma.

Pistil

The collective term for all the carpels of a flower.

Ovary

The part of the carpel that contains the ovules.

Stigma

The part of the carpel where pollen grains land and germinate.

Style

The part of the carpel that connects the stigma and ovary.

Megaspore

The haploid cell that undergoes meiosis in the ovule to form the female gametophyte.

Embryo sac

The female gametophyte in flowering plants, consisting of seven cells and eight nuclei.