Chromosomal distribution of cloned zein cDNA sequences in maize and teosinte

The occurrence of zein-like sequences in teosinte has been investigated using two zein cDNA clones, M1 and M6 (Viotti et al., EMBO J. 1, 1982), and the BamHI-XbaI fragment (616bp, E21) of the genomic clone E19 (Spena et al., J. Mol. Biol. 169, 1983, more than 96% homologous to pMGI cDNA clone) that define three of the four or more zein prototype sequences found in the inbred W64A. The three non-cross hybridizing zein sequences have been labelled with 3H-TTP by nick translation and then hybridized in situ to meiotic spreads of W64A, of two teosinte lines (Zea mays ssp. mexicana, race Chalco, and Zea mays ssp. parviglumis, race Balsas-Guerrero) and of F1 hybrids W64A x Z. mays mexicana and W64A x Z. mays parviglumis.

In all types of spread more than 140 meiocytes were analyzed, all having labelled chromosomes. The number of chromosomes showing hybridization and the hybridization sites per chromosome vary depending on the probe and on the line or hybrid investigated. In any case the silver grains per hybridization site were from three to five. Statistical analysis of the various parameters mentioned above indicated that M6 and E21 (pMGI) zein-like sequences were found in teosinte subspecies on the same chromosomes and sites as in maize: chr. 4 proximal 1/3 of long arm (M6+E21); chr. 7 distal 1/3 of short arm (M6+E21); chr. 10 distal 1/3 of long arm (M6). On the contrary the M1 probe showed in both teosintes in respect to maize an additional chromosomal hybridization site. In all the combinations tested (inbreds and hybrids) where teosinte chromosomes were present chromosomes 4 and 10 showed hybridization on the distal 1/3 of both long arms, while in maize line W64A only chr. 4 hybridized.

A. Viotti, N. Pogna and E. Sala
 
 


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