Fig. 4. Time course of GrlE expression. (A) Total RNA was extracted from wild-type AX4 cells harvested at the indicated time of development and electrophoretically separated on a 1.2% agarose gel before being transferred to a nylon membrane. The membrane was hybridized with a probe for grlE (see Materials and methods). (B) Samples were collected from wild-type and grlE^– null cells that had developed for 0, 4 and 16 hours, and probed for grlE mRNA. Consistent loading in each lane was confirmed by staining for rRNA.