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A maize genetic map based mainly on expressed sequences has been constructed. The map incorporates data from four segregating populations. Three recombinant inbred line populations were derived from the nonreciprocal crosses between three inbred lines. A map derived from an independent F2 progeny from one of the crosses was also used. With a total of 521 genotyped individuals, accuracy in gene order is expected. Five sources of markers were used: (i) 109 loci corresponding to 69 genes of known function, (ii) 39 loci controlling protein position shifts revealed by two-dimensional electrophoresis, (iii) 8 isozyme loci, (iv) 17 loci corresponding to 14 sequenced cDNAs for which no homology was found in gene banks, and (v) 102 loci corresponding to 81 anonymous probes. As many loci were common to all maps, we tested heterogeneity between recombination fractions. The comparison of recombination fractions revealed: (i) a good correspondence between the maps derived from the same cross, (ii) few significant differences in interval distances, and (iii) global differences, which can reach 20% of the total map length. A composite map of 275 loci covering 1765 cM has been constructed. Key words : Zea mays L., RFLP, genetic map, molecular markers, proteins.

The Drosophila gene pointed (pnt) is required for the differentiation of a number of tissues during embryogenesis, including the ventral ectoderm, the nervous system, the tracheal system and certain muscle fibers. The phenotypes associated with strong pointed alleles are reflected by a complex pointed expression pattern during embryogenesis. Two promoters, P1 and P2, separated by some 50 kb of genomic sequences, direct the transcription of two different transcript forms, encoding two different proteins related to the ETS family of transcription factors. To assess the individual functions of the two different pointed protein forms, we have generated new pointed alleles affecting either the P1 or the P2 transcript, termed P1 and P2 alleles, respectively. Genetic analysis reveals partial heteroallelic complementation between certain pointed P1 and P2 alleles. Surviving trans-heterozygous flies have rough eyes, abnormal wings and halters, suggesting a requirement for pointed function during their imaginal disc development. Further genetic analysis demonstrates that expression of a given pointed P2 allele depends on trans-acting transcriptional regulatory sequences. We have identified two chromosomal domains with opposite regulatory effects on the transcriptional activity of the pointed P2 promoter, one trans-activates and the other trans-represses pointed P2 expression. By deletion mapping we were able to localize these control regions within the 5' region of the pointed P2 transcript.