slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
第十章 基因和发育 PowerPoint Presentation
Download Presentation
第十章 基因和发育

Loading in 2 Seconds...

play fullscreen
1 / 48

第十章 基因和发育 - PowerPoint PPT Presentation


  • 134 Views
  • Uploaded on

第十章 基因和发育. The Genetic Basis of Development. By Hongwei Guo, Peking University, 2008.12. 概述. 遗传信息的载体 —DNA 和基因 遗传信息的传递 — 中心法则 遗传信息的调控 — 基因表达 基因表达调控的事例 — 疾病和 发育 拟南芥花发育的基因调控 果蝇胚胎发育的基因调控. Eye. Antenna. Leg. Wild type. Mutant. Use mutants to deduce developmental pathways.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about '第十章 基因和发育' - scarlett-hayes


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

第十章 基因和发育

The Genetic Basis of Development

By Hongwei Guo, Peking University, 2008.12

slide2
概述
  • 遗传信息的载体—DNA和基因
  • 遗传信息的传递—中心法则
  • 遗传信息的调控—基因表达
  • 基因表达调控的事例—疾病和发育
  • 拟南芥花发育的基因调控
  • 果蝇胚胎发育的基因调控
slide3

Eye

Antenna

Leg

Wild type

Mutant

  • Use mutants to deduce developmental pathways

Common Methodology

Arabidopsis

Drosophila

model organism s
Model organisms

DROSOPHILA MELANOGASTER

(Fruit fly)

CAENORHABDITIS ELEGANS

(Nematode)

ARABIDOPSIS THAMANA

(Arabidopsis)

The organism chosen for understanding broad biological principles is called a model organism.

MUS MUSCULUS

(Mouse)

DANIO RERIO

(Zebrafish)

No human,

why?

arabidopsis thaliana a genetic model plant
Arabidopsis thaliana (拟南芥): a genetic model plant
  • The advantages of using Arabidopsis as a model :
    • a small genome size: 125 Mb
    • a short generation time: 6-8 weeks
    • easy to grow, very small, and produces a lot of seeds
    • self-pollination, easy to cross
    • can be easily transformed
slide6

Flower Development

  • Transition from the vegetative to the reproductive phase.
transition from vegetative to reproductive development
Transition from Vegetative toReproductive Development
  • Controlled by developmental and environmental signals.
  • This transition is called flowering(开花) or bolting (抽苔) and results in the formation of the inflorescence meristem (花序分生组织), which produces floral meristem (花分生组织).
slide9

Flower development in Arabidopsis

Vegetative meristem

Inflorescence meristem

Transition to reproduction:

Genes & other factors

Floral meristem

Flower:

sepals, petals, stamens,

and carpels

Flower organ development:

Organ identity genes

slide11

The floral meristem produces 4 sets of floral organ primordia in concentric rings (called whorls)

    • Sepals - outer ring, 1st whorl
    • Petals- interior to the sepals, 2nd whorl
    • Stamens - interior to the petals, 3rd whorl
    • Carpels- inner ring, 4th whorl

拟南芥花的构成

genetic approach to flower development
Genetic Approach to Flower Development
  • Look for mutants
  • Analyze mutant phenotypes
  • Characterize genetic interaction
  • Clone genes – analyze gene expression
  • Sequence – biochemical properties
  • Transgenic plant – gain of function
organ identity mutants
Organ Identity Mutants

Wild-type

ap2

pi

ap1

ap3

ag

slide14

class

Genes

mutants

phenotype

APETALA1 (AP1)

APETALA2 (AP2)

ap1

ap2

A

APETALA3 (AP3)

PISTILLATA (PI)

ap3

pi

B

C

AGAMOUS (AG)

ag

Eliott Meyerowitz group, Caltech, 1980s-90s

genetic approach to flower development1
Genetic Approach to Flower Development
  • Look for mutants
  • Analyze mutant phenotypes
  • Characterize genetic interaction
  • Clone genes – analyze gene expression
  • Sequence – biochemical properties
  • Transgenic plant – gain of function
slide16

B

B

A

C

C

A

Sp

P

St

C

C

St

P

Sp

The ABC Modelfor Floral Organ Identity

(Sp)

(P)

(St)

(C)

the abc model
The ABC Model
  • Three classes of gene products
  • Combinatorial interactions to give rise to the four types of floral organs
    • A = sepals identity
    • A+B = petals identity
    • B+C = stamens identity
    • C = carpels identity
    • A and C mutually repress each other
floral homeotic genes in arabidopsis
Floral homeotic genes in Arabidopsis

Function

Gene products

APETALA1 (AP1)

APETALA2 (AP2)

A

APETALA3 (AP3)

PISTILLATA (PI)

B

C

AGAMOUS (AG)

loss of a function ap1 ap2 mutant s

B

B

A

A

C

C

Sp

P

St

C

C

St

P

Sp

B

B

C

C

St

C

C

C

St

St

St

C

Loss of A function-ap1, ap2 mutants

ap2

ap1

loss of b function apetala3 pistillata mutants

B

B

A

A

C

C

Sp

P

St

C

C

St

P

Sp

A

A

C

C

Sp

Sp

C

C

C

C

Sp

Sp

Loss of B function -apetala3/pistillata mutants

pi

ap3

loss of c function agamous mutant

B

B

A

A

C

C

Sp

P

St

C

C

St

P

Sp

B

B

A

A

Sp

P

P

Sp

Sp

P

P

Sp

Loss of C function–agamous mutant

ag

genetic approach to flower development2
Genetic Approach to Flower Development
  • Look for mutants
  • Analyze mutant phenotypes
  • Characterize genetic interaction
  • Clone genes – analyze gene expression
  • Sequence – biochemical properties
  • Transgenic plant – gain of function
loss of b and c functions results in all sepals

B

B

A

A

C

C

Sp

P

St

C

C

St

P

Sp

A

A

Sp

Sp

Sp

Sp

Sp

Sp

Sp

Sp

Loss of B and C Functions-- Results in all Sepals

ap3 ag

loss of a b c functions results in a flower with leaves in place of floral organs

B

B

A

A

C

C

Sp

P

St

C

C

St

P

Sp

Thus, leaves are default structures

---花是由叶变态而成的最直接的证据---

Loss of A,B, C Functions results in a ‘flower’ with leaves in place of floral organs

ap1 ap3 ag

L

L

L

L

L

L

L

L

genetic approach to flower development3
Genetic Approach to Flower Development
  • Look for mutants
  • Analyze mutant phenotypes
  • Characterize genetic interaction
  • Clone genes – analyze gene expression
  • Sequence – biochemical properties
  • Transgenic plant – gain of function
slide26

B

B

A

A

C

C

Sp

P

St

C

C

St

P

Sp

slide27

A, B, C gene mRNA expression pattern

revealed by in situ hybridization

AP1 AP3 AG

A

B

C

Exception: AP2 is expressed in all four whorls

genetic approach to flower development4
Genetic Approach to Flower Development
  • Look for mutants
  • Analyze mutant phenotypes
  • Characterize genetic interaction
  • Clone genes – analyze gene expression
  • Sequence – biochemical properties
  • Transgenic plant – gain of function
flower homeotic genes
flower homeotic genes
  • Floral homeotic genes or floral identity gene encode MADS-domain proteins
  • Proteins dimerize and bind to DNA to act as transcription factors
  • Are found in plants, fungi, animals
genetic approach to flower development5
Genetic Approach to Flower Development
  • Look for mutants
  • Analyze mutant phenotypes
  • Characterize genetic interaction
  • Clone genes – analyze gene expression
  • Sequence – biochemical properties
  • Transgenic plant – gain of function
slide31

B

B

A

A

C

C

Sp

P

St

C

C

St

P

Sp

B

B

A

A

C

C

P

P

St

St

St

St

P

P

PI/AP3:B function

35S::PI

35S::AP3

c mutant

35S::PI

35S::AP3

a mutant

35S::PI

35S::AP3

slide32

E class: SEP1, SEP2, and SEP3

are required for B and C functions

pi ag (BC)

double mutant

sep1 sep2 sep3

triple mutant

wild type

slide33

SEP1, SEP2, SEP3 = E class

  • MADS box proteins (most similar to AP1)
  • Have redundant function
  • Single mutants show subtle phenotype
  • Triple mutant similar to bc double mutant
  • Interact with B and C proteins

Q: How was this triple mutant obtained?

(hint: reverse genetic approach)

revisionist abc model

B

A

C

sepal

petall

stamen

carpel

E

“Revisionist” ABC Model
meristem identity genes
Meristem Identity Genes
  • Floral transition activates genes important for reproductive meristems, called meristem identity genes
    • Promote the floral meristem identity
      • LEAFY (LFY)
      • APETALA1 (AP1) with CAULIFLOWER (CAL)
      • APETALA2 (AP2)
    • Maintenance of meristem identity
      • TERMINAL FLOWER -- inflorescence meristem
      • AGAMOUS– fully committed floral meristem
floral meristem mutants
Floral Meristem Mutants

Wild-

type

lfy

ap1

ap1 + cal

lfy + ap1

lfy meristem identity gene
LFY: meristem identity gene
  • In strong lfy mutants, sepals, petals, and stamens are placed by leaf-like organs, bracts, carpels are formed by abnormal
  • LFY is expressed in the inflorescence meristem that will form the floral meristem, and in the floral meristem
  • The LFY protein is a plant-specific transcription factor
lfy is both necessary and sufficient for abc gene expression
LFY is both necessary and sufficient for ABC gene expression
  • In lfy mutants, AP1 expression is delayed and reduced
  • In lfy mutants, AP3 and PI expressed is reduced
  • In lfy ap1 double mutant, AG expression is abnormal
  • Ectopic expression of LFY can cause ectopic AP1, AP3 and AG expression (what could be the phenotype of 35S::LFY?)
a model for lfy function in activating abc genes
A Model for LFY Function in Activating ABC Genes

FM precursor

FM

Sepal

St + Ca

Pe + St

IM

IM

IM

IM

LFY Expression

LFY and AP1 Expression

LFY and AG Expression

LFY, AP3, and PI Expression

IM: Inflorescence Meristem

FM: Floral Meristem

so lfy can activate ap1 expression

How Does LFY Activate ABC Genes?

So, LFY can activate AP1 Expression
  • To study LFY activity, a fusion of LFY to a inducible protein, GR, was made.
  • In the absence of the glucocorticoid hormone, GR-LFY is inactive;
  • When the hormone is present, GR-LFY becomes active.
  • When LFY-GR was inactive, AP1 expression was not activated, when LFY-GR was active, AP1 was activated.
is this activation direct regulation test of direct regulation

LFY

Gene X

Protein X

LFY

AP1

AP1

Activates Transcription

Activates Transcription

Is this activation direct regulation?---test of direct regulation
slide42
LFY binds to cis elements of the AP1 gene
    • EMSA (Electrophoresis Mobility Shift Assay)
    • ChIP (Chromatin Immunoprecipitation)
  • LFY activates AP1 expression when there is no new protein synthesis
    • Cycloheximide treatment (inhibit translation)
  • Therefore, the activation of AP1 by LFY is direct
similarly lfy also directly regulates ag

H

B

X

H

S

E3

E2

2.98kb

GUS

Similarly, LFY also directly regulates AG
  • This fragment contains two LFY-binding sites
  • If the sites are mutated, then LFY does not bind
  • These mutant fragments cannot support LFY induced expression

The AG cis-regulatory elements reside in the second intron,~200 bp fragment

slide45

Transition to reproduction

Flower

?

Inflorescence

Vegetative phase

Reproductive phase

slide46

Factors regulating the transitions

  • Genes (flowering-time genes and floral identity genes)
  • Day length (photoperiod)
  • Temperature (vernalization)
  • Hormones (GA, etc)

Vegetative meristem

Inflorescence meristem

Floral meristem

slide47

(春化)

(光周期)

LFY

A, B, C, E genes

slide48

Take home questions:

  • What are the common criteria for those model organisms?
  • If you want to make a plant flower early, what gene(s) will you overexpress in that species?
  • Can you turn a leaf into a floral organ? how?
  • Can you get a plant producing flowers with stamens and carpels outside while sepals and petals inside?
  • If you think ABC model is not correct or complete, what could be your evidence?