Technological exploration of BAC-FISH on mitotic chromosomes of maize

The rice BAC-DNA was used as probes and fluorescence in situ hybridization (FISH) was applied to the interphase and metaphase mitotic chromosomes of maize. To optimize the BAC-FISH technique, we respectively assayed the effect of several factors, including maize or rice genomic C o t DNA used as blocking reagent of DNA, washing temperatures and FAD concentration in the washing buffer and in the hybrid solution. The results show that C o t DNA of maize genome blocked the repetitive sequence of the rice BAC-DNA when the C o t value was below 50. Meanwhile, it was necessary to adjust the C o t value according to the different probes and their ratios. Decreasing the concentration of FAD in the hybridization mixtures, adjusting the washing rate after hybridization, and most especially, blocking the ricespecific repetitive sequences of BAC-DNA could improve the positive signals of BAC-FISH.