FIG. 7.
Accumulation of SpEts4 message precedes activation of the SpHE gene. Levels of SpEts4 and SpHE mRNAs were assayed by RNase protection with both probes combined in the same reactions and hybridized with total RNA isolated from eggs or embryos at the indicated stages of development. Hours postfertilization are indicated, as are the corresponding developmental stages (Cl, cleavage; VEB, very early blastula; B, blastula; G, gastrula; P, pluteus). Samples in the last two lanes serve as markers and are the RNase-resistant fragments for each single probe (E, SpEts4; S, SpHE) after hybridization to early-blastula-stage RNA. The left two lanes show unhybridized SpHE and SpEts4 probes (PS and PE, respectively). Lane C, negative control with both probes hybridized with yeast tRNA. The lower panel shows the ethidium bromide-stained gel of egg and embryo RNA samples, demonstrating that equal quantities of intact RNAs were used in these reactions.