QUANTITATIVE EXPRESSION OF MAIZE HSPS - GENETIC DISSECTION AND ASSOCIATION WITH THERMOTOLERANCE

In higher plants, within-species qualitative polymorphism for heat sho ck proteins (HSPs) is extremely rare, even between genotypes showing d ifferent heritable levels of thermotolerance. Here we have explored th e amount of quantitative variability in HSP synthesis in maize. We hav e analyzed the quantitative expression of the typical HSPs in a set of recombinant inbreds (RIs) derived from the F1 hybrid between a thermo tolerant (T232)- and a thermosensitive (CM37)-genotype, characterized for about 200 mapped RFLP loci. Significant differences were detected in the level of expression of five HSPs, and their frequency distribut ion in the RI population is that of a quantitative trait. Subsequent m apping of loci controlling the characters, based on RFLP analysis, con firmed the multigenic control of HSP expression: the regression analys is of the band intensities of each variant HSP on RFLPs revealed, for the different HSPs, a minimum number of three to eight quantitative tr ait loci (QTLs) accounting for a high proportion (0.35-0.60) of the ge netic variability of these bands. An analysis of the correlation betwe en the variability of HSPs and that of cellular membrane stability, a cellular component of thermotolerance, did not reveal any significant association of the two parameters.