A METHOD FOR EXAMINING EXPRESSION OF HOMOLOGOUS GENES IN PLANT POLYPLOIDS

One of the essential issues regarding evolution of polyploid species i s how duplicate genes are expressed. Most studies on gene expression i n polyploids have been based on isozyme analyses; RNA analysis has not been widely used partially due to difficulties in distinguishing homo logous transcripts which usually have the same length and similar or a lmost identical sequences. In this study, a method combining RT-PCR wi th RFLP was used to analyze transcripts of homologous genes in natural and synthetic Brassica amphidiploids. Sequences coding for several kn own genes were selected and used to synthesize gene-specific primers. Total RNAs were used as templates for RT-PCR to amplify homologous tra nscripts in three diploid parental species, three cultivated amphidipl oid species and six synthetic amphidiploids. For each gene, initial PC R products amplified in all species had identical length; however, hom ologous transcripts in the diploid and amphidiploid species-could be d istinguished after digesting the PCR products with restriction enzymes . Preliminary results based on three genes indicated that both transcr ipts from the diploid parents were expressed in the synthetic and natu ral amphidiploids. This study represents the first application of RT-P CR and RFLP analysis to investigate expression of homologous genes in higher plants. The technique is a sensitive, simple and efficient meth od for distinguishing homologous transcripts in a mixed RNA population and can be applied to many types of studies on expression of homologo us genes.