wg transcript distribution follows a similar pattern to the protein. Transcripts are first detected at early nuclear cycle 14 and remain strong through germband extension. They are first detected in the posterior region, starting slightly before anterior expression and posterior wg protein expression. At mid nuclear cycle 14, levels of the posterior band have increased and transcripts for segmental bands begin to appear in anterior segments. In early gastrulation, each segment has a thin stripe of wg mRNA and the posterior wg band is most intense. At stage 7, the posterior stripe remains strong and moves dorsally to form the "midgut plate". At stage 10, the posterior tissue expressing wg invaginates to later form the hindgut.

wg transcript is detected in the late third instar larval wing disc in a stripe that corresponds to the future wing margin and in two concentric rings that encircle the wing pouch. The inner wing gives rise to the distal hinge structures and the outer ring gives rise to proximal hinge structures. An additional stripe of wg expression marks the future mesonotum.

At 5 h after egg laying (AEL), wg is expressed in two rings of the hindgut, the inner covering the presumptive tubule primordia.

In early embryos wg transcript is expressed in two anterior domains and one broad posterior domain.

Expression of wg is seen in several domains of the wing disc, including two rings surrounding the wing pouch, the inner of which develops into the more distal stripe running through the adult wing hinge.

en and wg are expressed in imaginal discs from the time the imaginal disc cells segregate from the larval epidermis until the end of the third larval instar. wg is generally expressed in the anterior portions of the imaginal discs.

wg transcription is repressed by ectopic eve protein in eve^hs.PS embryos. Timing suggests that eve is a direct regulator of wg.

wg expression is seen on the ventral side of the proctodeum and then in the primordia of the Malphigian tubules as they evert from the proctodeum. As the tubules grow, wg is associated with the posterior side of each tubule.

wg is expressed in parasegment 8 in the mesoderm. This expression is abolished in abd-A, Ubx, and dpp^s4 homozygotes.

wg transcripts are most abundant in 3-6hr embryos and in pupae and are detectable at all other stages tested. wg transcripts are first detected in blastoderm embryos at the anterior pole and in a ring around the posterior end. They accumulate in a series of stripes, one per metameric unit in the extended germband. At germ band shortening, the stripes are 3-5 cells wide and include the most posterior cells of the anterior compartment of each segment. wg transcripts are also detected in the CNS, hindgut, procephalic lobe, labrum, and the analia.

The wg transcript is expressed in 16 evenly spaced stripes 2-3 cells wide in germ band extended embryos. Additional hybridization is detected in the procephalic lobe and the anterior head region.

At the larval neuromuscular junction, wg protein is localized at large type Ib synaptic boutons in a dynamic pattern of punctuate distribution at the synaptic interface between motor neuron and muscle.

wg protein is detected in the intestinal stem cells, enteroblasts, and enteroendocrine cells in the posterior midgut epithelium.

The first expression of wg protein appears during cellularization of the blastoderm. At mid nuclear cycle 14, posterior wg appears in a band at 10% egg length. Two patches of anterior expression at 85% and 100% egg length are seen. This is before the appearance of any segmental stripes. As blastoderm stage progresses, the posterior stripe becomes stronger and remains the most prominent region of wg expression during gastrulation and early germ band extension. The segmental stripes appear sequentially from anterior to posterior during late cell cycle 14 blastoderm stage. During early gastrulation (stage 6), all 14 of the segmental stripes are formed and a strong posterior band of wg remains at 10% egg length. By late gastrulation, the posterior wg band migrates to a region called the midgut plate, which invaginates at the extended germ band and eventually forms the hindgut. wg is found in the future hindgut. The expression of the posterior band of wg was compared to other gap and pair-rule genes. wg is expressed subsequent to hb protein and appears during cellularization of the blastoderm in a narrow band posterior to the posterior hb stripe. Kr is first detected during late syncytial blastoderm but wg posterior expression just posterior to the Kr domain appears at mid nuclear cycle 14. eve antigen is first detected at the early blastoderm stage. wg posterior band expression occurs at mid nuclear cycle 14 posterior to the seventh eve stripe.

wg is expressed in all dorsal and ventral abdominal histoblast nest in segments A1-7 in females at 26hr APF. In males, expression is absent in segment A7 at 26hr APF.

At 0 and 5 hours after the second to third instar larval transition, wg is expressed in a stripe in the presumptive wing margin. At 10 hours, a ring of wg appears around the wing pouch. A faint patch of wg is visible in the notum at 15 hours and is more clearly resolved by 25 hours.

wg protein is not detected in embryonic lymph glands; expression is first detected in majority of lymph gland cells in newly-hatched first instar larvae, and is uniformly expressed in hematopoietic cells of the lymph gland through mid-second instar. At mid-to-late second instar, wg protein expression is down-regulated in the forming cortical zone of the lymph gland; a drop in wg expression in differentiating hemocytes occurs prior to those cells expressing the hemocyte marker Hml. wg protein expression is maintained in prohemocytes in the medullary zone through late third larval instar; expression is also observed in crystal cells in the cortical zone of the lymph gland. Late in the third larval instar, a second wave of wg protein expression occurs in mature Hml-expressing hemocytes.

wg protein accumulates between the luminal surface of the circular muscles and the basement membrane of the gut epithelia. Weak accumulation is also seen in intestinal stem cells.

In third instar wing disc, wg is expressed distally

in a stripe of cells that will form the adult wing margin and, proximally, in the inner and outer rings. The limit of wg expression in the inner ring coincides proximally with the proximal limit of rn expression and distally with both the distal limit of zfh2 and the proximal limits of dve and nab expression.

wg is expressed in the anterior and posterior boundary cells of the embryonic proventriculus.

At embryonic stage 16, wg is expressed in svp-expressing cells in segments A5-A7. At 30-36 hr APF, wg is expressed transiently in svp-expressing cells in segment A1-A5.

wg protein isdetected in two concentric rings toward the edges of the wing disc and in a stripe along the dorsal/ventral boundary of the wing pouch.

wg protein is detected in the procephalic neurectoderm from stage 8 onward in a domain spanning a broad area of the ocular and anterior antennal segment. Additional domains of wg expression include a small spot of expression in intercalary segment and a expression in the dorsal hemispheres of the clypeo-labral segment. 25% of the neuroblasts in the protocerebrum are wg positive as well as 3 neuroblasts in the deutocerebrum and a single neuroblast in the tritocerebrum.

Expression in procephalic neuroblasts stage 9-11: tritocerebrum - d4; deuterocerebrum - d1, d7, d8; protocerebrum - cd1, cd3, cd6, cd7, cd10-13, pd1, pd3, pd4, pd6, pd7, pd9, pd12, pd13

Strong wg protein expression was observed in glutamatergic type 1b synaptic boutons at the larval neuromuscular junction. The protein was observed both pre- and post-synaptically and evidence indicates that it is secreted from the pre-synaptic neuron and taken up by the post-synaptic muscle cell.

Using conventional staining techniques wg protein is detected in a stripe on the apical side of the presumptive notum. However, when an inactive form of fz2 that is still able to bind the wg protein is overexpressed in the underlying mesoderm, wg protein can be detected in the mesodermal tissue indicating that wg can diffuse across germ layers.

The wg protein is expressed in a specified subset of neuroblasts in embryonic stages 8-11. (see also FBrf 49374)

The expression pattern of wg protein in wg^hs.P embryos, 3 hours after heat shock, is similar to that in nkd mutant embryos.

wg expression was observed in 5 regions which are anterior to the centers of en expression. These are the "wg antennal stripe", the "wg head blob", the "wg intercalary spot", the "wg expression in the foregut" and the "wg labral spot". The relative positioning of the wg- and en-expressing cells was followed.

wg protein expression is seen on the ventral side of the proctodeum and then in the primordia of the Malpighian tubules as they evert from the proctodeum. As the tubules grow, wg protein is associated with the posterior side of each tubule.

The wg protein is expressed in the embryo in a each parasegment, in a 4-5 cell width stripe, just anterior to en expressing cells. Electron microscopy revealed that the wg protein accumulates in the cytoplasm of the wg expressing cells, and is then detected in the ECM and in en expressing cells. It seems that the wg protein is passed directly from cell to cell. wg protein is also detected up to two cell widths away from wg expressing cells.

In strong arm alleles, wg RNA is no longer detectable in embryos by late stage 9.

wg protein does not accumulate in the visceral mesoderm in embryos lacking abd-A. Its expression pattern is unchanged in Ubx mutants and in embryos with ectopic Ubx expression. wg expression is severely reduced in embryos lacking Ubx and its surrounding regulatory regions.