THE MATERNAL to ZYGOTIC TRANSITION in HIGHER PLANTS

Question 1

1. Zygote Development and Embryogenesis in Angiosperms

Angiosperms alternate between sporophytic and gametophytic generations. Male and female sporophytes produce _____ and _____, respectively, which develop into male and female gametophytes.

Answer 1

microspores and megaspores

Question 2

1. Zygote Development and Embryogenesis in Angiosperms
   Fertilization Process

Male gametophyte, or pollen, germinates and produces a ______.

It grows through the female _____ to deliver sperm cells to the female gametophyte, typically consisting of seven cells (4)

Answer 2

pollen tube

pistil

three antipodal cells
two synergid cells
one egg cell
one central cell

Question 3

1. Zygote Development and Embryogenesis in Angiosperms

One sperm cell + egg cell

Other sperm cell + central cell (nourishes the developing embryo)

Answer 3

diploid zygote

triploid primary endosperm cell

Question 4

Early Embryogenesis part 1:

Embryogenesis is a key process in higher plant development, and early morphological events during this period have been well described in a number of species, such as _____ and _____

The _____ is the start of embryogenesis.

After fertilization, the zygote undergoes various changes, such as the disappearance of the large ____ in the egg cell.

The nucleus moves to the center, signaling a transition to a symmetrical state without polarity.

Zygote elongation begins, a cell wall is synthesized, and polarity develops with the nucleus moving to _____.

Answer 4

Arabidopsis thaliana
Nicotiana tabacum

zygote

vacuole

one end

Question 5

Early Embryogenesis part 2:

Another large vacuole is generated, and the nucleus moves to the _____ of the zygote.

The zygote divides asymmetrically into a smaller ____ (develops to embryo) and a larger _____ (develops to suspensor with distinct developmental fates.

The suspensor’s uppermost cell, the _____, becomes part of the primary root meristem.

Cells from the suspensor and embryo proper differentiate into various tissue types.

Answer 5

chalazal end

apical cell
basal cell

hypophysis

Question 6

First major transition in the life of higher plants animals

Represents a critical phase during early embryogenesis where genetic control transitions from maternal to zygotic (newly formed embryo) influence.

Answer 6

maternal-to-zygotic transition

Question 7

The Maternal-to-Zygotic Transition (MZT) During Early Angiosperm Embryogenesis
Process:

_______: Involves the degradation of RNA and proteins that were present in the egg prior to fertilization.

_____ Gradual activation of the embryo’s own genome to begin transcribing its own RNA, marking a significant developmental milestone.

Answer 7

Clearance of Maternal Transcripts and Proteins

De Novo Activation of Zygotic Genome

Question 8

Timing of the MZT in Higher Plants:

((How they found out when the zygote begins to rely on its own genome for directing development, rather than depending on maternal RNA and proteins deposited in the egg. ))

Inhibitors used to study:
transcription inhibitors like ______, which targets _____, to delineate when zygotic transcription is necessary for continued embryo development. By applying this inhibitor at different stages and observing developmental consequences, researchers can infer when the zygotic genome must be active.

Answer 8

α-amanitin
RNA polymerase II

Question 9

Timing of the MZT in Higher Plants:

Technical Limitations:
Plant zygotes and early embryos are typically encased within _____, making them difficult to access and manipulate compared to animal systems. This complicates the direct study of ZGA.

Species Variability:
There is significant variability across different plant species in the timing of ZGA, suggesting that plant embryogenesis can be subject to diverse regulatory mechanisms that may not be universally applicable.

Answer 9

ovules

Question 10

Fertilized egg cell starts with ____ which leads to ____ that initiates ____ leading to ____ which leads to ____ forming _____

Answer 10

maternal control
zygote
ZGA initiation
elongated zygote
two-celled proembryo

Question 11

in higher plants is a critical phase within the maternal-to-zygotic transition (MZT) where the embryo starts transcribing its own genes. This step is pivotal as it marks the point where the developmental control begins to shift from the maternal to the embryonic genome.

Answer 11

Zygotic Genome Activation (ZGA)

Question 12

ZGA in higher plants:

Researchers use ____ to compare the profiles of embryos at various stages to determine when zygotic transcripts first appear. Techniques include RNA sequencing and quantitative PCR.

By inhibiting _____ and observing effects on embryo development, researchers can infer the timing and impact of ZGA.

Answer 12

transcriptome analyses

RNA polymerase activity

Question 13

ZGA in higher plants challenges:

Detecting Low-Abundance Transcripts: can be present in _____very low numbers, making them difficult to detect against the background of abundant maternal RNA.

Answer 13

Early zygotic transcripts

Question 14

CRISPR

Made out of?

Answer 14

Clustered regularly interspaced short palindromic repeats

gRNA

Cas9

Question 15

First developmental event that requires transcription of zygote genome:

Answer 15

Midblastula Transition (MBT)

Question 16

inhibits translation

inhibits DNA replication

Answer 16

Cycloheximide

Aphidicolin

Question 17

Cells of what species inactivate a-amanitin?

Answer 17

Daucus carota

Question 18

____ binds to DNA transcription initiation complex and intereferes w/e longation of RNA chain by RNA polumerase, impairing DNA replication

_____ incorporates into RNA, inhibits transcription, elongation, because of absence of hydroxyl moiety

Answer 18

Actinomycin D

Cordycepin

Question 19

Three critical time points in MZT

Answer 19

1. initiation of degradation of maternal transcripts after fertilization
2. Onset of zygotic genome transcription
3. Replacement of parental transcript

Question 20

4.1 Current Methods for Isolating Gamete Cells and Early Embryos:

_____ This method allows for precise isolation of specific cells using a fine glass needle under a microscope.

_____ enables rapid isolation of specific cell types based on their fluorescence characteristics, but it requires relatively large initial cell volumes.

_____ offers high-resolution isolation of target cells from their surroundings using a laser beam, though it usually yields small cell numbers of somewhat diminished RNA quality.

Answer 20

Microdissection

Fluorescence-Activated Cell Sorting (FACS)

Laser Capture Microdissection (LCM)

Question 21

4.2 Current Approaches Toward Single-Cell Sequencing:

______ While osmotic shock-based methods are rapid, they suffer from RNA degradation issues, whereas poly(A) selection strategies yield intact mRNA but may lose non-polyadenylated informative RNAs.

_____ PCR-based amplification efficiently constructs cDNA libraries, but linear mRNA amplification allows for the amplification of low-level templates from a limited number of starting cells.

Answer 21

Single-Cell mRNA Extraction

Construction of Single-Cell cDNA Libraries

Question 22

4.3 Current Techniques Used to Detect De Novo Synthesized Transcripts:

_____ enables the identification of de novo-synthesized transcripts but may suffer from “false positive” cDNAs, mitigated by methods like mirror orientation selection (MOS).

_____ detects transcriptional changes, its application in plants has been limited compared to animals.

_____ This method provides insights into transcriptome changes at different developmental stages, aiding in the identification of de novo-synthesized transcripts.

Answer 22

Suppression Subtractive Hybridization (SSH)

RNA Fluorescence In Situ Hybridization (RNA-FISH)

Time-Resolved Expression Profile Analysis

Question 23

4.4 Current Approaches to Distinguish Paternal from Maternal Transcripts:

______ This method effectively distinguishes paternal from maternal transcripts based on SNP differences but may require modifications for reliable discrimination.

_____ SSR-based RT-PCR offers a method to distinguish parental transcripts but is limited by the fewer number of SSR sites compared to SNPs.

_____ This method detects parental-origin transcripts but may be influenced by T-DNA chromosomal insertion sites.

_____ SNP-based RNA-seq provides quantitative insights into parental contributions but requires analysis of transcriptome profiles and SNP differences between parental genomes.

Answer 23

Allele-Specific RT-PCR

Simple Sequence Repeat-Based RT-PCR

GFP/GUS Reporter-Based Analysis

SNP-Based RNA-seq