The talin head is essential for integrin function in <i>Drosophila</i>.

<p>(<b>a–c</b>) Maternal-zygotic talin null embryos (shown in a) rescued with either full-length WT talinGFP transgene (b) or headless talinGFP transgene (c) and stained for F-actin (green) and integrin (magenta). (<b>d–f</b>) Integrin-dependent phenotypes germband retraction (d), dorsal closure (e) and muscle attachment (f) were assayed in talin-null embryos, WT-talin-rescued embryos, and headless-talin-rescued embryos. The talin head was required for all three processess assayed. Scale bar = 100 µm. (<b>g–h</b>) Recruitment of ubi-promoter driven, GFP-tagged full-length WT talin and headless talin to sites of adhesion was assayed in wild-type embryos (g) and in a talin null background (h). In a WT background, headless-talinGFP competed less well with endogenous talin and was only weakly recruited to sites of adhesion compared to WT (***p<0.001); in the absence of endogenous talin, headless-talin was well recruited to sites of adhesion. (<b>i</b>) FRAP experiments on talinGFP-WT and headless-talinGFP reveal that headless talin is much less stable at sites of adhesion than talinGFP-WT. (<b>j–m</b>) Confocal z-stacks of stage 17 maternal/zygotic-mutant embryos rescued with either full length WT talin (j,l) or headless-talin (k,m). (<b>j–k</b>) adhesions stained for talin (green in j–k; grey in j′–k′) and integrin (red in j–k). In the absence of the talin head, talin was still well recruited. (<b>l–m</b>) Muscles stained for talin (magenta in l–m) and paxillin (green in l–m; grey in l′–m′). Paxillin was not well recruited to adhesions. Scale bars: a–e = 100 µm; j–m = 20 µm.