Fig. 5. (A) Confirmation of the micro-array results for four selected ESTs. In a micro-array screen of 1700 ESTs, using RNAs from growing Dd-STATb+ and Dd-STATb-cells to make the labelled cDNAs, 38 ESTs showed a reproducible difference in hybridisation (see Table 1). Several of the characterised ESTs (i.e. those where the Dictyostelium gene had previously been described or, in the case of HGPRT, where a function could be inferred) were employed as probes in northern transfer, using RNAs extracted from cells growing in HL5 medium and at the indicated densities. In some cases, different northern blots were used for different analyses. A loading control was performed for each blot, using the constitutively expressed gene Ig7, and in each case the control confirmed the changes visualised here (data not shown). (B) Comparison of the levels of discoidin 1 gene expression in multiple Dd-STAb+ and Dd-STATb-clone. Independent clones from the same transformation, using the Dd-STATb disruption construct, were screened for Dd-STATb expression by immunostaining. Five `random integrant' clones (clones B12-16), where the blasticidin resistance cassette inserted non-homologously into the genome, and five Dd-STATb disruptant clones (B5, B6, B8, B9 and B10) were analysed by northern transfer using a discoidin 1 probe. The loading control shown was performed on the same blot, by melting off the discoidin 1 hybridisation signals and then using, as a probe, the constitutively expressed gene Ig7.