Effect of <i>lz</i> on Scab Formation and the Other Events of Puncture Wound Healing

<div><p>(A and B) Posterior of <i>lz⁺</i> (<i>w¹¹¹⁸</i>) (A) and <i>lz^r15</i> mutant (B) L3 larvae. Larvae were heated so crystal cells appear as tiny black dots. No crystal cells are apparent in the <i>lz^r15</i> mutant. Bar, 200 μm.</p> <p>(C and D) Micrographs of control <i>lz⁺</i> (<i>w¹¹¹⁸</i>) (C) and <i>lz^r15</i> mutant (D) L3 larvae 4 h after puncture wounding. No scab is seen at the <i>lz^r15</i> wound site (encircled). Bar, 50 μm.</p> <p>(E and F) TEM sections through 24-h–old puncture wounds of a control <i>lz^r15</i>/+ heterozygote (E) and a hemizygous <i>lz^r15</i> mutant larva (F), both carrying the <i>msn-lacZ</i> transgene. A consolidated, electron-dense scab has formed in the control larva (E), but only a diffuse plug with peripheral electron density is present at the <i>lz^r15</i> hemizygous wound (F). The electron density of the <i>lz^r15</i> plug might be due to residual melanization activity in the <i>lz^r15</i> mutant. Although reepithelialization is complete in the <i>lz^r15</i> mutant wound, the epidermis contains large vacuoles and abundant apical processes, and it is separated by a gap (asterisks) from the old cuticle and has not secreted new cuticle. Other 24-h <i>lz^r15</i> mutant wounds analyzed had necrotic or discontinuous epidermis at the wound site (not shown). Bar, 10 μm.</p> <p>(G and H) Fluorescence micrographs of 20-h puncture wounds in control (G) and <i>lz^r15</i> mutant (H) larvae carrying the <i>msn-lacZ</i> reporter that were treated as above and immunostained for Fasciclin III (red) and β-galactosidase (green). Epidermal cells at both control and <i>lz^r15</i> mutant wounds have fused to form syncytia (arrows), and cells in the control are oriented toward the wound site (arrowheads). The orientation response of epidermal cells in the <i>lz^r15</i> mutant is difficult to assess because cell borders out to six cell diameters away from the wound appear slack and wavy. Bar, 50 μm.</p> <p>(I–L) X-gal stains of 6-h–old puncture wounds of control <i>lz⁺</i> (I and K) or <i>lz^r15</i> hemizygous mutant larvae (J and L) carrying either <i>msn-lacZ</i> (I and J) or <i>puc-lacZ</i> (K and L). Note the absence of scabs and the increase in reporter activity (blue) in <i>lz^r15</i>. The basal level of reporter expression in unwounded epidermis was not increased in <i>lz^r15</i> (not shown).</p> <p>Bar, 50 μm.</p>