(A-B”’) Stage 16 wild type w1118 and exp135 embryos were stained with anti-Gasp (MAb 2A12) (blue), chitin probe (red), and anti-Piopio (green). (A-A”’) In w1118 embryos, Gasp (2A12), chitin, and Piopio accumulate in the lumen of all branches. (B-B”’) In exp135 mutant embryos, Piopio accumulates in all branches like in wild type. However, Gasp (2A12) and chitin only accumulate in the lumen of DT but not other branches. (C, D) Similar to wild type embryos, Verm is secreted to the lumen in all branches in exp135 mutants. However, in LT, Verm (orange arrowhead) in exp135 mutants is slightly weaker compared to wild type LT (white arrowhead).