RAPD markers encoding retrotransposable elements are linked to the male sex in Cannabis sativa L.

Male-associated DNA sequences were analyzed in Cannabis sativa L. (hemp), a dioecious plant with heteromorphic sex chromosomes. DNA was isolated from male and female plants and subjected to random amplified polymorphic DNA analysis. Of 120 primers, 17 yielded 400 to 1500-bp fragments detectable in male, but not female, plants. These fragments were cloned and used as probes in gel-blot analysis of genomic DNA. When male and female DNA was hybridized with 2 of these male-specific fragments, MADC(male-associated DNA sequences in C. sativa)3 and MADC4, particularly intense bands specific to male plants were detected in addition to bands common to both sexes. The MADC3 and MADC4 sequences were shown to encode gag/pol polyproteins of copia-like retrotransposons. Fluorescence in situ hybridization with MADC3 and MADC4 as probes revealed a number of intense signals on the Y chromosome as well as dispersed signals on all chromosomes. The gel-blot analysis and fluorescence in situ hybridization results presented here support the hypothesis that accumulation of retrotransposable elements on the Y chromosome might be 1 cause of heteromorphism of sex chromosomes.