Table 4.

Antisense RNAs transcribed within the ORF or 5' UTR of genes involved in heterocyst differentiation

Gene	Gene Function	Gene Expression After Nitrogen Step-down	RNA Location	Antisense RNA Expression After Nitrogen Step-down
narB (alr0612)	nitrate reductase	increased by 12 h	narB ORF and 5' UTR	no change
fraH (alr1603)	cell-cell connection	increased by 12 h	alr1603 ORF	slight decrease by 21 h
alr3649	heterocyst specific ABC transporter	increased by 12 h	5' end of alr3649 ORF into upstream gene	increased by 12 h
alr3479	similar to nitrogen regulation protein NtrR	decreased slightly at 6 h only	alr3479 ORF	increased by 21 h
glnB (all2319)	nitrogen assimilation	no change	glnB 5' UTR	no change
hetR (alr2339)	heterocyst differentiation regulator	increased by 6 h	hetR ORF and 5' UTR	decreased by 21 h
hetC (alr2817)	heterocyst differentiation	increased by 12 h	two RNAs, one in hetC ORF and one in hetC-hetP intergenic region	increased by 12 h
hetF (alr3546)	heterocyst differentiation	no change	hetF ORF and 5' UTR; NsiR1*	increased by 6 h
all3558	nitrogen assimilation regulation	no change	all3558 ORF	increased by 21 h
hepK (all4496)	exopolysaccharide synthesis	increased by 12 h	hepK ORF; contains repeat sequence at 5' end	no change
nblA	phycobilisome degradation	increased by 12 h; largest increase at 21 h	nblA ORF and 5' and 3' UTRs	antisense transcription until 12 h only
hglE (alr5351)	heterocyst-specific glycolipid	increased by 12 h; largest increase at 21 h	hglE 3' end of ORF	increased by 12 h
hglD (alr5354)	heterocyst-specific glycolipid	increased by 21 h	hglD ORF and 5' UTR	no change
hglC (alr5355)	heterocyst specific glycolipid gene	increased by 6 h; largest increase at 21 h	hglC ORF	increased at 6 h only

*NsiR1 has been previously characterized [40].