REGULATION and GENE EXPRESSION in PLANT DEVELOPMENT

Question 1

______ connect genetics and development by establishing the chain of events from gene activity to morphological differences.

Hierarchies of gene interactions dictate the size, shape, and structure of plants through coordinated regulation.

Answer 1

Regulatory genes

Question 2

Which are italicized? Gene symbols or proteins?

Answer 2

Genes

Question 3

By the ____ of embryogenesis (approximately four days after fertilization), all principal elements of the plant body are established.

_____ of the hormone auxin begins early and is crucial for defining the embryo’s main axis and central vasculature.

Answer 3

heart stage

Apical-to-basal transport

Question 4

Auxin Flux and Plant Development
Key Components:

_____ DNA sequences in the promoters of auxin-inducible genes.

_____ A family of proteins that bind to AREs and regulate gene expression.

_____ Transcriptional repressors that interact with ARFs to inhibit gene expression.

Answer 4

ARE (Auxin Response Element):

ARF (Auxin Response Factor):

Aux/IAA

Question 5

Auxin Flux and Plant Development
Mechanism of Action:

Auxin as a _____:
Auxin binds to the TIR1/AFB protein complex, facilitating the interaction between Aux/IAA proteins and the SCF-type E3 ubiquitin ligase complex.

______:
Components: Skp1, Cullin1 (Cul1), Rbx1, and the TIR1/AFB protein.
The complex tags Aux/IAA proteins with ubiquitin (Ub) via a cascade involving E1 (ubiquitin-activating enzyme) and E2 (ubiquitin-conjugating enzyme).

Answer 5

Molecular Glue

SCF E3 Ubiquitin Ligase Complex

Question 6

Auxin Flux and Plant Development
Mechanism of Action:

Degradation of Aux/IAA:
Polyubiquitinated Aux/IAA proteins are targeted for degradation by the _____, removing repression from ARE-containing promoters.

Activation of Transcription:
Once Aux/IAA repressors are degraded, ARFs can activate transcription of _____, leading to various developmental responses.

Answer 6

26S proteasome

auxin-inducible genes

Question 7

Auxin Flux and Plant Development

_____ indicates the sites of organ initiation and development, mediated by the dynamic localization and function of PIN proteins.

Answer 7

Auxin maxima

Question 8

Auxin Flux and Plant Development

_____ are auxin efflux carriers that facilitate the directional transport of auxin across cells, establishing auxin gradients essential for plant development. Predicts where auxin will be.

____ is localized to the basal membrane of inner cells in the _____, mediating ____

_____ localizes to the_____of suspensor cells and reportedly triggers weak expression of a _____ in the proembryo.

Answer 8

PIN proteins

PIN1
proembryo
basal-to-apical transport

PIN7
apical membranes
DR5 reporter gene

Question 9

Auxin Flux and Plant Development

_____ postulates that auxin acts to polarize its own transport, this canalization is an important part of the mechanism that underlies coordinated tissue polarization

_____ constructs are synthetic auxin-responsive promoters used to visualize transcriptional responses to auxin. They help determine the positions of auxin perception maxima, essential for studying auxin’s role in organogenesis and cellular differentiation.

Answer 9

Canalization hypothesis

DR5: Reporter Gene

Question 10

Key Genes and Pathways in Plant Development:

regulate cell division and expansion, particularly in (maintaining the stem cell population) in the shoot apical meristem (SAM).

Answer 10

WOX Family and WUSCHEL (WUS)

Question 11

Key Genes and Pathways in Plant Development:

regulates membrane trafficking (endosomal recycling) of auxin-efflux carrier PIN1 essential for the correct (localization of PIN proteins) and therefore proper auxin distribution and embryonic pattern formation.

points to auxin drainage

alterthe asymmetric division of the zygote and interfere with the formation of distinct apical-basal regions in the developing embryo.

regulates the formation of vesicles in membrane trafficking

Answer 11

GNOM Gene

Question 12

Key Genes and Pathways in Plant Development:

_____ pathway plays a major role in (establishing different cell fates) post-zygotic division, influencing basal cell lineage towards (forming the suspensor)

_____ iestablishing different cell fates after the first zygotic division.

Answer 12

YODA (YDA)

MAPK kinase gene

Question 13

Key Genes and Pathways in Plant Development:

_____ may play a role complementary to YDA and promotes normal development of the apical cell into a proembryo

Answer 13

Auxin

Question 14

Key Genes and Pathways in Plant Development:

_____ Works within the YDA pathway to determine suspensor identity

its protein in the leaf epidermis is sufficient to activate YDA-dependent signaling

Answer 14

SHORT SUSPENSOR (SSP)

Question 15

Key Genes and Pathways in Plant Development:

____ a transcription factor responsive to auxin, is required for primary root formation and vascular development.

Stabilizing mutations in____can be suppressed by the overexpression of MP

Aux/IAA proteins act as inhibitors of MP

It may directly activate transcription of PIN1.

Answer 15

MONOPTEROS (MP) Gene

Question 16

Apical and Basal:

____ and _____mark the upper-tier cells between the 8-cell

______
mark the lower-tier cells between the 8-cell

______ genes normal patterning of the apical domain

_____ involved in maintenance of shoot fates

Answer 16

WOX2 and CUC3

PLETHORA 1 (PLT1)

GURKE/PASTICCINO (GK/PAS)

TOPLESS (TPL)

Question 17

Globular Stage

______ Promotes central or adaxial cell fates.
Dominant alleles resistant to microRNA increase the size of the embryonic SAM and promote adaxial characters.

____ and ____
Promote central or adaxial cell fates.
Expressed in the center of the upper tier and the adaxial sides of developing cotyledons.

____ and _____
Define the peripheral domain.
Promote abaxial or peripheral cell fates.

______
Binds microRNAs and mediates the degradation of target transcripts.
Enhances effects of rev loss-of-function alleles.

Answer 17

PHB (PHABULOSA)

PHV (PHAVOLUTA) and REV (REVOLUTA)

KANADI (KAN) and YABBY (YAB)

ARGONAUTE (AGO)

Question 18

Regulation of Leaf Development:

______
Promote abaxial cell fates and help maintain leaf bilateral symmetry.
KAN1 is expressed in the peripheral cells of the lower tier and the abaxial side of cotyledon primordia.

_____
Detected at the late globular stage, marks the abaxial side of cotyledon primordia.
Promotes blade outgrowth in lateral organs.

_____
Expressed in lateral organs and promotes differentiation by repressing meristematic characteristics.

Answer 18

KANADI Genes

FILAMENTOUS FLOWER (FIL)

AS1 (ASYMMETRIC LEAVES1)

Question 19

Medial Stage

_____
A homeodomain gene of the KNOTTED family.
Establishes medial and lateral gene expression domains at the late globular stage.
Prior to cotyledon outgrowth, redirects auxin flux towards incipient primordia.

_____
Mediates redistribution of PIN proteins from basal to apical localization.

Answer 19

SHOOTMERISTEMLESS (STM)

PID (PINOID)

Question 20

_______ Establish expression domains defining the medial domain separating cotyledon primordia.
Repress cell proliferation and differentiation to generate a boundary.

Initiate expression of STM in the medial domain.

Answer 20

CUP-SHAPED COTYLEDON (CUC) Genes (CUC1, CUC2, CUC3)

Question 21

Hypocotyl and Embryonic Roots

______ Encode AP2 class transcription factors essential for QC specification and stem cell activity.
Expression confined to provascular cells above the hypophysis.

______ Regulates asymmetric cell division and radial organization of the root.
Required for stem cell maintenance in the root meristem.

_______
Works with SCR to maintain the root meristem.

Answer 21

PLETHORA (PLT1, PLT2) Genes

SCARECROW (SCR)

SHORT-ROOT (SHR)

Question 22

Hypocotyl and Embryonic Roots

_____ Required for root meristem formation.
Affects hypophysis derivatives and limits auxin responses to actively dividing cells.

_____ Involved in maintaining adjacent tissue initials in an undifferentiated state during QC function.

_____ Involved in specifying hypophysis fate and root development.

Answer 22

HOBBIT (HBT)

RETINOBLASTOMA-RELATED (RBR)

WOX (WUSCHEL-related homeobox) Genes (WOX5, WOX8, WOX9/STIMPY)