Expression pattern of sigN genes during multicellular development. A. RNAs from WT and srfA- strains were collected at the indicated hours (0–30) or at the slug stage of development (slug). The coding region of the sigN1 gene was used as probe for hybridization. The mRNA detected migrated faster than the 18S rRNA. Ethidium bromide staining of the gel is shown in the lower panel. Hybridization signals were quantified by densitometry and normalized for the rRNA present in each lane (lower graphic). The value obtained for the 12 hours sample of the WT strain was considered 100% of expression. B. RNA was obtained from WT (AX4) strains, collected at the indicated hours of development. SigN genes expression was determined by RT-PCR using oligonucleotides specific for each group of genes. The sequence amplified for both groups was about 240 bp, and the control sequence, obtained by amplification of a region of the large mitochondrial ribosomal RNA, about 320 bp. Bands were quantified by densitometry, normalized in relation to the control and represented in a bar graphic, assigning 100% expression to the16 hours sample for Group 1 and 14 hours sample for Group 2.