[Physical mapping of the genes px and cld coding peroxidase and cold-regulated protein in maize (Zea mays L.)]

Peroxidase plays a key role in plant disease resistance, cold stress and some developmental processes, and cold-regulated protein functions necessarily in reaction of plants on cold or heat stress. Recent studies showed that these processes in plant cells were involved in programmed cell death (PCD). Using a biotin-labelled in situ hybridization (ISH) technique, we physically mapped the genes px and cld coding peroxidase and cold-regulated protein respectively onto maize chromosomes. Both DAB and fluorescence detection systems gave the identical results, the probe uaz235 corresponding to gene px was localized onto the long arm of chromosome 2 (2L) and 7L, and csu19 corresponding to gene cld was hybridized onto 4L and 5L. The percentage distances (from the hybridization sites to centromeres) of uaz235 in 2L and 7L were 45.4 +/- 1.3 and 67.4 +/- 3.7 respectively, and those of csu19 in 4L and 5L were 68.6 +/- 2.6 and 58.2 +/- 1.6 respectively. The physical positions of px in 2L and cld in 4L coincide with those in their genetic map pattern. The results also show that both of these genes have duplicated sites in maize genome.