In situ hybridization by Ddpngase DIG labeled RNA probes. The in situ hybridization with the Ddpngase antisense probe showed high expression during the loose (a) and the tight (b) aggregate stages. The expression was more concentrated in the tip (pstA) region (c) though posterior prespore region also showed faint expression. The expression of Ddpngase was highest in the prestalk B/AB cells and rear-guard cells (RGC) (d and e). The mid culminant (f) and the culminant (g) showed the expression in the upper (UC) and lower cups (LC) and the basal disc (BD) regions. The negative control in situ hybridization using sense RNA probes did not develop significant color or background staining (data not shown). The different regions in the multicellular structures needing particular attention are marked.