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Lecture 12

MCD BIO C141 Lecture Notes - Lecture 12: Meristem, Eudicots, Epistasis


Department
Molecular, Cell, and Developmental Biology
Course Code
MCD BIO C141
Professor
Jeffery Long
Lecture
12

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MCDB C141 Week 8 Lect 1
-Recall the key steps of stomata development
-Recognize how stomata development is a model for stem cells
-Summarize the function and timing of stomata regulators
Stomata: a pore, found in the epidermis of leaves, stems, and other organs, that facilitates gas
exchange.
guard cell: specialized plant cells in the epidermis of leaves, stems and other organs that are used to
control gas exchange.
subsidiary cells: A plant epidermal cell that is located next to a guard cell in the stoma of a leaf and
differs in structure from other epidermal cells. Also called accessory cell.
pavement cell: a cell type found in the outmost epidermal layer of plants. The main purpose of
these cells is to form a protective layer for the more specialized cells below
protodermal cell: The outermost layer of cells across the top of the apical meristem and leaf
primordium is a meristem called this. its cells are still dividing and their progeny cells will develop into
epidermis cells.
meristemoid mother cell (MMC): undergoes asymmetric entry divisions and produces a meristemoid
(M) as well as a larger sister cell
meristemoid: undergo asymmetric amplifying divisions before differentiating into a guard mother cell
(GMC)
stomatal lineage ground cell (SLGC): can differentiate into a pavement cells or reacquire a MMC fate and
initiate asymmetric spacing divisions that produce “satellite meristemoids.
guard mother cell (GMC): cells surrounding each stoma. They help to regulate the rate of transpiration
by opening and closing the stomata.
initiation: the first step in the process of gene transcription, the process of transcribing or making a
copy of genetic information stored in a DNA strand into a complementary strand of mRNA
amplification: The process of increasing the magnitude of a variable quantity, especially the magnitude
of voltage, power, or current, without altering any other quality. b. The result of such a process
differentiation: The process by which cells or parts of an organism change during development to serve
a specific function.
SPEECHLESS (SPCH): Transcription factor acting as an integration node for stomata and brassinosteroid
(BR) signaling pathways to control stomatal initiation and development. Activates transcription when in
the presence of SCRM/ICE1. Functions as a dimer with SCRM or SCRM2 during stomatal initiation.
Required for the initiation, the spacing and the formation of stomata, by promoting the first asymmetric
cell divisions. Together with FMA and MUTE, modulates the stomata formation. Involved in the
regulation of growth reduction under osmotic stress (e.g. mannitol), associated with a quick decrease of
meristemoid mother cells (MMCs) number lower stomatal index and density
SCREAM1/2 (SCRM1/2):
MUTE: Transcription factor. Together with FMA and SPCH, regulates the stomata formation. Required
for the differentiation of stomatal guard cells, by promoting successive asymmetric cell divisions and the
formation of guard mother cells. Promotes the conversion of the leaf epidermis into stomata.

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FAMA: Transcription activator. Together with MYB88 and MYB124, ensures that stomata contain just
two guard cells (GCs) by enforcing a single symmetric precursor cell division before stomatal maturity.
Together with SPCH and MUTE, regulates the stomata formation. Required to promote differentiation
and morphogenesis of stomatal guard cells and to halt proliferative divisions in their immediate
precursors. Mediates the formation of stomata. Prevents histone H3K27me3 marks and derepresses
stem cell gene expression
Retinoblastoma (Rb): a rare form of cancer that rapidly develops from the immature cells of a retina,
the light-detecting tissue of the eye. It is the most common primary malignant intraocular cancer in
children, and it is almost exclusively found in young children.
Stomata Development
Small pores on the epidermis of the leaf and stem , in later development, might be on the adaxial side of
the leaf
Allow for gas and water exchange
Density can be controlled by the environment, senses how much CO2 and H20 is in the environment and
adds the stomata accordingly
Form through amplifying divisions on the epidermis precursors act as a type of meristem
Do not develop synchronously
Stoma is Greek for mouth or opening
Development controlled by a cascade of transcription factors and signaling molecules
Stomata Structure
Two guards cells surround the stoma or
stomata
Structure found in most eudicots like
Arabidopsis
Epidermal cells sometimes referred to as
pavement cells
Is there a mutation that can get rid of a
certain part of the stomata? If so, what would happen to the leaf? Concern yourself with phenotype of
spchless, screen 1, 2 and mute. No stomata, plants develop, but it is very sick because there is no gas
exchange
No two stomata can be next to each other
Stomata structure in monocots
Slightly different structure in monocots (grasses)-they also have subsidiary cells
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