Evolutionary relationships in the genus Zea: analysis of repetitive sequences used as cytological FISH and GISH markers

Evolutionary relationships in the genus Zea: analysis of repetitive sequences used as cytological FISH and GISH markers

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The present study is a revision of our work on evolutionary cytogenetics of the genus Zea, including several new experiments which give a deeper insight into the nature of the DNA sequences involved in telomeric regions of Basketball - Shoes - Junior Zea luxurians.These new experiments, based on the Southern blotting technique and in situ hybridization, have demonstrated the following: 1) in situ hybridization (FISH) demonstrated the presence of the 180-bp repeat maize-knob-repeat-sequence in DAPI-positive terminal heterochromatic blocks of Z.luxurians (ZL-THB region); 2) Southern blot analysis confirmed that the 180-bp repeat present in maize is also present in Z.

diploperennis, Z.luxurians and Tripsacum dactyloides, but not in Z.perennis; 3) another sequence with targeted sites for endonucleases, but without recognition sites for the 180-bp repeat, may be interspersed with the 180-bp repeat in a tandem array sited in the ZL-THB region; 4) in situ hybridization (GISH) of probes Scale and blocking-probes with chromosomes of Z.

luxurians (using Z.luxurians as a probe and Z.diploperennis or Z.

perennis as a blocking-probe) gave strong fluorescence in both cases.Since Z.diploperennis possesses the 180-bp repeat, fluorescence on Z.

luxurians chromosomes was not expected.These results can be explained if the ZL-THB regions are composed not only of 180-bp repeats interspersed with other sequences, but also of other tandem arrays unique to Z.luxurians, which, according to our GISH results, are probably located at the subterminal position.