Fig. 5. ato is regulated by Dll and hth, but not ss and the a2-a3 joint is defective in ato null antenna. (A) Wild type, (B) ato¹ and (C) Df(3R)ss^D114.4/ss^D115.7 second antennal segments (a2). Arrows in A and C indicate the circular outline of the a2-a3 joint which is normal in ss mutant antenna, but absent in the ato¹ antenna in B. ato expression is lost in a hypomorphic Dll antenna (D) and in hth null clones (F and F'), but not in a ss null (Df(3R)ss^D114.4/ss^D114.9) antenna disc (E). Ato is green in all panels. Hth is red in F. Arrowheads in D and E indicate Ato in the eye.