Lecture 6

• Anterior posterior axis formation-the posterior signal

• Anterior posterior axis formation-down the hierarchy

Lab 3

208 or 210: P{hsp ftz 273-303 ry+}

226: P{hsp ftz 3-413 ry+}

Lab 5

166 refers to embryos laid by DH502 females crossed with DH302 males.

167 refers to embryos laid by DH502 females crossed with DH301 males.

Consult Hyduk and Percival-Smith for the genotypes associated with the above strain names. See Table 1 and Figure 5.

The mutant allele used for the engrailed and wingless experiments was ftz13.

Pole cell transplantationMosaic analysis

Cellular Blastoderm

Egg chamber

Example

pipe (pip) Toll (Tll)

What cells, follicle or germ-line, are pipe and Toll required in?

Pole cell transplantationMosaic analysis

OvoD

No eggs

Pole cell transplantationMosaic analysis

OvoDWild type

Pole cell transplantationMosaic analysis

OvoDWild type

Wild type

Active egg chamber get eggs produced

Toll

Genotype of follicle cells

Tll lf wtTll lf dorsalized dorsalizedGenotype

of oocytepole cells wt wt wt

pipe

Genotype of follicle cells

pipelf wtpipelf dorsalized wtGenotype

of oocytepole cells wt dorsalized wt

Posterior signal

Three classes of maternal effect phenotypes

Nusslein-Volhard et al., Science 238, 1675-1681

Nusslein-Volhard et al., Science 238, 1675-1681

What was done to show that nanos was the best candidate to encode the posterior signal?

Pole cell formationLocus Pole cells

nanos +

pumilio +

oskar -

staufen -

vasa -

tudor -

valois -

nanos

Injection of oocyte cytoplasm

nanos

Injection of nurse cell cytoplasm

Injection of stage 10 cytoplasmGenotype ofdonor

Oocyte% rescue

Nurse cell% rescue

wild-type 40 66

nanos 0 0

pumilio 33 56

oskar 74 66

staufen 52 87

vasa 72 95

valois 31 100

tudor 9 35

Nanos isolationexpression

Wang and Lehmann Cell 66, 637-647

Nanos isolationlocalization

Wang and Lehmann Cell 66, 637-647

Nanos isolationrescue

Wang and Lehmann Cell 66, 637-647

Nanos and maternal Hunchback expression

Nanos

Hunchback

Expression of Hunchback from maternal mRNA

Nanos Maternal Hunchback expression

Larvae lacking both maternal and zygotic hb exhibit a stronger phenotype

hb/hb

Irish et al., Nature 338, 646-648

Larvae lacking both maternal and zygotic hb exhibit a stronger phenotype

hb/hb

hb/hb OvoD mat hb-

hb-

hb+

Pole cell transplantation

Irish et al., Nature 338, 646-648

Larvae lacking both maternal and zygotic hb exhibit a stronger phenotype

hb/hb

mat hb-

hb-

Irish et al., Nature 338, 646-648

Maternal Hunchback is dispensable for normal development

hb/hb

mat hb-

hb+

hb-

Irish et al., Nature 338, 646-648

Nanos phenotype

Irish et al., Nature 338, 646-648

hb/hbnos/nos OvoD mat nos- hb-

hb+

Pole cell transplantation

Nanos has no role when mat hb is removed

Irish et al., Nature 338, 646-648

Two polar centers regulate Hunchback expression

Wharton and Struhl Cell 67, 955-967

Nanos regulatory sequences in the 3’ UTR of mat hb

Wharton and Struhl Cell 67, 955-967

Hunchback expression

Wharton and Struhl Cell 67, 955-967

Nanos represses bicoid translation

mRNA

protein

Wang and Lehmann Cell 66, 637-647

What Nanos and Pumilio do to suppress Hunchback

Gilbert Developmental Biology 7th ed

Microtubules and the transport of Nanos and Bicoid mRNA

Gilbert Developmental Biology 7th ed

Hunchback lacks anterior segments

Nusslein-Volhard and Wieschaus 1980 Nature 287, 795

Gap proteins

Transcription factors

Hunchback is a morphogen

Delineate blocks of pattern along the A-P axis

Gap information used to set up the striped expression of pair-rule genes

100% egg length 0%

HB

TLLa TLLpGTa GTpKr Kni

Expression of some Gap proteins

100% egg length 0%

HB

TLLa TLLpGT GTKr KniKni

Posterior signal is permissive because the terminal protein Tailless supresses GT expression. The termini provide polarity.

100% egg length 0%

HB

GTpKr Kni

Hunchback gradient and the regulation of gap genes

Hunchback gradient and the regulation of gap genes

Regulatory rules

medium [HB] activates Kr

medium [HB] represses Kni

low [HB] represses gtp

100% egg length 0%

HB

GTpKr Kni

Outcome of the regulatory rules

Expression of FTZ and EVE

Lawrence The making of a fly

Eve stripe 2 regulatory element

Gilbert Developmental Biology 7th ed

lacZ

Stripe two element expression

100% egg length 0%

HB

GTa Kr

BCD

100% egg length 0%

HB

GTa Kr

BCD

EVE stripe two

Stripe 2 regulatory rules

BIC and HB activate EVE stripe 2 expression

KR and GT repress EVE stripe 2 expression

Stripe 2 cis-regulatory elements

lacZHBKRBCD GT

lacZ

lacZ

lacZ

lacZ

100% egg length 0%

HB

GTa Kr

BCD

EVE stripe two

Stripe 2 cis-regulatory elements

lacZHBKRBCD GT

lacZ

lacZ

lacZ

lacZ

Stripe 2 trans-regulatory factors

lacZHBKRBCD GT

lacZ

lacZ

lacZ hb/hb

gt/gt

Kr/Kr

Expression of FTZ and EVE

The expression of pair-rule gene is the first evidence of segmentation; however, the cellular blastoderm embryo is not overtly segmented morphologically. Prepattern.

Lawrence The making of a fly

Establishing wingless and engrailed expression

Gilbert Developmental Biology 7th ed

Maintaining the boundary

Gilbert Developmental Biology 7th ed

You are segmented but not all segments are equal.

Homeotic selector genes are required for determining segmental identity.

Homeosis

Homeotic mutation

Antennapedia can be misexpressed either by spontaneous mutation or by genetic engineering.

Antenna to second leg transformation

The classic Ultrabithorax phenotype: the four winged fly

wild type

Ubx

Proboscipedia

pb tarsus

proboscis

Homeotic gene complexes and expression

Gilbert Developmental Biology 7th ed