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Four Scenarios ago, you chanced upon a provocatively located sequence similar to a protein binding site. If experiments demonstrated that this sequence upstream from the gene hetQ indeed binds the transcriptional regulator NtcA, then HetQ might be the missing link that connects perception of nitrogen starvation by cyanobacteria to the differentiation of specialized N2-fixing heterocysts!
You chose to do those experiments and months later found that: (a) NtcA DOES bind upstream from hetQ, but (unfortunately) (b) regulation of hetQ expression by NtcA is NOT responsible for the control of heterocyst differentiation by nitrogen availability. Oh well. The missing link is thus still missing. How to go about finding it? |