Changes in cspL, cspP, and cspC mRNA abundance as a function of cold shockand growth phase in Lactobacillus plantarum

An inverse PCR strategy based on degenerate primers has been used to identi fy new genes of the cold shock protein family in Lactobacillus plantarum. I n addition to the two previously reported cspL and cspP genes, a third gene , cspC, has been cloned and characterized. All three genes encode small 66 amino-acid proteins with between 73 and 88% identity. Comparative Northern blot analyses showed that the level of cspL mRNA increases up to 17-fold af ter a temperature downshift, whereas the mRNA levels of cspC and cspP remai n unchanged or increase only slightly (about two- to threefold). Cold induc tion of cspL mRNA is transient and delayed in time as a function of the sev erity of the temperature downshift. The cold shock behavior of the three cs p mRNAs contrasts with that observed for four unrelated non csp genes, whic h all showed a sharp decrease in mRNA level, followed in one case (bglH) by a progressive recovery of the transcript during prolonged cold exposure. A bundance of the three csp mRNAs was also found to vary during growth at opt imal temperature (28 degrees C). cspC and cspP mRNA levels are maximal duri ng the lag period, whereas the abundance of the cspL transcript is highest during late-exponential-phase growth. The differential expression of the th ree L. plantarum csp genes can be related to sequence and structural differ ences in their untranslated regions. It also supports the view that the gen e products fulfill separate and specific functions, under both cold shock a nd non-cold shock conditions.