Lecture 6 Anterior posterior axis formation-the posterior signal Anterior posterior axis formation-down the hierarchy

Lab or 210: P{hsp ftz  ry + } 226: P{hsp ftz ry + }

Lab 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 ftz 13.

Pole cell transplantation Mosaic analysis Cellular Blastoderm Egg chamber

Example pipe (pip)Toll (Tll) What cells, follicle or germ-line, are pipe and Toll required in?

Pole cell transplantation Mosaic analysis Ovo D No eggs

Pole cell transplantation Mosaic analysis Ovo D Wild type

Pole cell transplantation Mosaic analysis Ovo D Wild type Active egg chamber get eggs produced

Toll

pipe

Posterior signal

Three classes of maternal effect phenotypes Nusslein-Volhard et al., Science 238,

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

Pole cell formation

nanos Injection of oocyte cytoplasm

nanos Injection of nurse cell cytoplasm

Injection of stage 10 cytoplasm

Nanos isolation expression Wang and Lehmann Cell 66,

Nanos isolation localization Wang and Lehmann Cell 66,

Nanos isolation rescue Wang and Lehmann Cell 66,

Nanos and maternal Hunchback expression Nanos Hunchback

Expression of Hunchback from maternal mRNA

NanosMaternal Hunchback expression

Larvae lacking both maternal and zygotic hb exhibit a stronger phenotype hb/hb Irish et al., Nature 338,

Larvae lacking both maternal and zygotic hb exhibit a stronger phenotype hb/hb Ovo D mat hb - hb - hb + Pole cell transplantation Irish et al., Nature 338,

Larvae lacking both maternal and zygotic hb exhibit a stronger phenotype hb/hb mat hb - hb - Irish et al., Nature 338,

Maternal Hunchback is dispensable for normal development hb/hb mat hb - hb + hb - Irish et al., Nature 338,

Nanos phenotype Irish et al., Nature 338,

hb/hb nos/nos Ovo D mat nos - hb - hb + Pole cell transplantation Nanos has no role when mat hb is removed Irish et al., Nature 338,

Two polar centers regulate Hunchback expression Wharton and Struhl Cell 67,

Nanos regulatory sequences in the 3’ UTR of mat hb Wharton and Struhl Cell 67,

Hunchback expression Wharton and Struhl Cell 67,

Nanos represses bicoid translation mRNA protein Wang and Lehmann Cell 66,

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 TLLp GTa GTp KrKni Expression of some Gap proteins

100% egg length 0% HB TLLa TLLp GT KrKni Posterior signal is permissive because the terminal protein Tailless supresses GT expression. The termini provide polarity.

100% egg length 0% HB GTp KrKni 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 GTpKrKni 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 lacZ HBKRBCDGT lacZ

100% egg length 0% HB GTa Kr BCD EVE stripe two

Stripe 2 cis-regulatory elements lacZ HBKRBCDGT lacZ

Stripe 2 trans-regulatory factors lacZ HBKRBCDGT 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