Reading: The Maternal-to-Zygotic Transition in Higher Plants

Question 1

___ marks the turnover from the gametophyte to sporophyte generation in higher plants.

After fertilization,___ undergoes ___ from maternal to zygotic control: the____

Answer 1

Fertilization

sporophytic development
genetic turnover

Maternal-to-zygotic transition (MZT)

Question 2

1. Angiosperm life cycle
2. Male and female sporophytes produces___ which will develop into ___

Answer 2

1. Alternates between sporophytic and gametophytic
2. Microspores (male gametophytes); Megaspores (female gametophytes)

Question 3

The early male gametophyte, or pollen, germinates and produces a pollen tube that grows through the female pistil to deliver a pair of sperm cells to the female gametophyte, which usually consists of seven cells of four different cell types:

Answer 3

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

Question 4

a nutritive tissue supporting early embryonic development
sperm + central cell =

Answer 4

triploid endosperm

Question 5

marks the turnover from gametophyte to sporophyte development.

the starting point for embryogenesis.

Answer 5

fertilization

zygote

Question 6

___ 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 ___

1. it is also a series of fundamental and complex developmental events occur

Answer 6

Embryogenesis

Arabidopsis thaliana and Nicotiana tabacum

Question 7

The uppermost suspensor cell, termed the ___, eventually becomes part of the primary root meristem.

Answer 7

hypophysis

Question 8

The process of fertilization and embryogenesis in higher plants (7)

Answer 8

Fertilization:
Mature female gametophyte
Fertilized female gametophyte

Embryogenesis:
Elongated zygote
Two-celled proembryo
16-celled embryo
Globular embryo
Heart-shaped embryo

Question 9

The small apical cell develops into the ____ of the
embryo proper, whereas the larger basal cell continues to expand longitudinally and divides transversely to form a ____. The uppermost suspensor cell, termed the ___, eventually becomes part of the ____.

Answer 9

main body
suspensor
hypophysis
primary root meristem

Question 10

MZT meaning and definition

Answer 10

Maternal-to-Zygotic Transition
- It is a critical phase during embryogenesis when sporophytic development undergoes genetic turnover from maternal to zygotic control

Question 11

The MZT is the first major transition in the life of higher plants and animals and has been divided into two processes:
or
Two major coordinated molecular events occur during early embryogenesis:

Answer 11

1. Clearance of maternal transcripts and proteins deposited in the egg cell
2. Gradual de novo activation of
   zygotic genome transcription (hallmark of the MZT)

Question 12

Three critical time points
are evident during the MZT; these are-

Answer 12

1. initiation of degradation of maternaltranscripts after fertilization
2. the onset of zygotic genome transcription
3. the replacement of parental transcripts with zygotic transcripts.

Question 13

The _____ inanimals represents the first developmental event that requires transcription of
the zygotic genome, often being defined by blocking zygotic genome transcriptional activity with pharmacological inhibitors.

What are those inhibitors

Answer 13

midblastula transition (MBT)

• α-amanitin (RNA polymerase II and III inhibitor)
• actinomycin D
• cordycepin
  ( both inhibits transcription elongation of RNA chain by RNA polymerase)

Question 14

___ and ___were strongly affected by both actinomycin D and cordycepin.

This suggests that the onset of de novo transcription of the genome occurs before or during the ___

Also, ___are likely required for elongation and division of the zygote

Answer 14

Zygotic division
elongation

zygote elongation stage

de novo zygotic transcripts

Question 15

Transcription activator-like
____ and ____-based genome editing technology have been developed to knock out genes. These techniques have been widely used to perform reverse genetic studies in plants.

Answer 15

effector nucleases

clustered regularly interspaced short palindromic repeats (CRISPR)- based genome

Question 16

____ method of genome engineering can be used to efficiently and conveniently edit the plant genome. + cell-and-tissue genome editing.

Answer 16

CRISPR-based method

Question 17

The timing of MZT in higher plants. (A) In N. tabacum,

1. ___ occurs about
   ___ after pollination (HAP).
2. The zygote becomes ___ in ___ and asymmetrically
   divides ___.
3. Right after fertilization, about ___, male transcripts can be detected in zygotes.

Answer 17

48 h- Fertilization

96 HAP- Zygote Elongated
108 HAP

60 HAP- Male transcripts detected

Question 18

In A. thaliana embryogenesis, Fertilization occurs about ___ and the zygote starts to divide ___.

The ___ could also be detected at the ___ stage.

Answer 18

8 HAP
24 HAP

male transcripts
early zygote

Question 19

Figure 2. The timing of MZT in higher plants. (+ illustrate)

Answer 19

N. Tabacum
- Egg cell
- Fertilized egg cell
- Zygote
- Elongated zygote
- Two-celled proembryo

A. thaliana
- Egg cell
- Zygote
- Elongated zygote
- 16-celled embryo
- Globular embryo

Question 20

is the first event of gene expression after fertilization

Answer 20

ZGA- Zygotic genome activation

Question 21

Loss-of-function mutants defective in early embryonic development have helped to define the MZT in animals. Two different classes of mutants
are useful in this context.

The first is ___ exhibiting
embryonic developmental defects; these can be used to explore the roles played by maternal factors.

The second class is -__,
which are useful to detect contributions made by de novo zygotic transcripts.

Answer 21

maternal-effect mutants

zygotic recessive mutants

Question 22

___ is a traditional method used to isolate tissue-specific cells; a fine glass needle is manipulated under an inverted microscope to assist in dissection.

Answer 22

Microdissection

Question 23

is a specialized type of flow cytometry that “rapidly separates labeled living cells” of particular types from a heterogeneous mixture of different cell types, based on the specific fluorescence characteristics and light-scattering properties of the target cells

Answer 23

Fluorescence-activated cell sorting (FACS)

Question 24

___ is a high-resolution method used to isolate cells from their surrounding tissues, with the aid of a laser beam, under direct microscopic visualization. Specific cells can be isolated directly

Answer 24

Laser capture microdissection (LCM)

Question 25

Current methods for Isolating Gamete Cells and Early Embryos

Answer 25

Microdissection

Fluorescence-activated cell sorting (FACS)

Laser capture microdissection (LCM)

Question 26

1st Current method of single-cell RNA-seq:

Answer 26

Single-Cell mRNA Extraction
- RNAs in sperm, egg cell, early embryos b4 the 8-cell stage) are released automatically following osmotic shock with a buffer, and
can be reverse transcribed.
- Limitation: cannot be stored for long period since that RNA in the shock buffer are easily degraded

Question 27

2nd Current method of single-cell RNA-seq:

Answer 27

Construction of Single-Cell cDNA Libraries
- PCR-based amplification

Question 28

Current Techniques Used to Detect De Novo Synthesized Transcripts

pcr based chuchu

Answer 28

Suppression Subtractive Hybridization (SSH)

Question 29

Current Techniques Used to Detect De Novo Synthesized Transcripts

2. Another useful method employed to detect transcriptional changes and has been applied to identify nascent transcripts within the animal nucleus However, in plants, RNA-FISH has been applied only to detect de novo A. thaliana endosperm

Answer 29

RNA Fluorescence In Situ Hybridization (RNA-FISH)

Question 30

Current Techniques Used to Detect De Novo Synthesized Transcripts

3.Comprehensive transcription profile analyses of sperm cells, egg cells, and early embryos, will help identify de novo-synthesized transcripts in early embryos.

4. ____ of embryos at different stages will help identify de novo-synthesized embryonic transcripts. This method requires isolation of embryos from successive stages

Answer 30

3. Transcription Profile Analysis of Gamete Cells and Embryos
4. Time-Resolved Expression Profile Analysis

Question 31

Current Approaches to Distinguish Paternal from Maternal Transcripts.

1. A simple method used to distinguish paternal from maternal transcripts based on SNP differences between the two alleles (low cost and short time)
2. are useful molecular markers; usually feature repetitive di- or tri-nucleotide repeats, which can be used in conjunction with PCR and gel electrophoresis to detect different transcripts identified by the lengths of the PCR products.
3. Reciprocal crosses between nontransgenic and transgenic plants carrying the GFP/GUS reporter gene can be efficiently used to detect early embryonic transcription
4. A powerful tool used to study changes in the transcriptome during the MZT of plants. The relative parental contributions can be quantified based on analysis of SNPs that distinguish the two parental genomes.

Answer 31

1. Allele-Specific RT-PCR;
2. Simple Sequence Repeat-Based RT-PCR (SSRs)
3. GFP/GUS Reporter-Based Analysis
4. SNP-Based RNA-seq

Question 32

Conclusion: What did we learn from the kuan

Answer 32

When the MZT commences,

When zygotic genome transcription commences

The contributions of parental transcripts to early embryogenesis; all seem to differ from those of animals

Question 33

Recommendation

Answer 33

More reliable in vitro culture systems and microinjection techniques for fertilized egg cells should be established for plants.

Question 34

CRISPR meaning

Answer 34

Clustered Regularly Interspaced Short Palindromic Repeats