Fig. 2.

The mef2 requirement of target genes correlates with the start of their expression. (A) In situ hybridizations of wild-type embryos for Act57B, CG17492, CG5080, Mlc2, Mlc1, CG6972, and Mhc at different stages of development as indicated. Genes that only need low levels of mef2 activity (Act57B and CG17492) are at the top, and those that require the highest levels (CG6972 and Mhc) are at the bottom. (B) Graph, with fitted line from linear regression, showing the correlation between the requirement for mef2 and when the gene is first activated for 16 genes known to be expressed specifically in muscle at stage 13. The requirement for mef2 is taken as the expression of each gene at stage 13 in mef2⁴²⁴ embryos relative to wild type. The start of expression was compiled from in situ hybridizations (A) (refs. 33 and 34 and data not shown).