Plant & Animal Genome VII Conference Plant & Animal Genome VII Conference
W15
Microsatellites are generally regarded as type II markers for which no known functions are established. Type I markers are associated with genes of known functions. They are more important in comparative mapping studies to determine evolutionary relationships between different species and facilitate mapping of genes (Vs markers), but polymorphic type I markers are relative rare in catfish. To develop polymorphic type I markers, microsatellite-enriched libraries were established by priming a single-stranded catfish pituitary cDNA library using (CA)15 and (GA)15 primers. The enriched cDNA libraries were screened to obtain microsatellites-containing cDNA clones. From a total of 50 CA- and GA-positive clones, 39 clones were revealed to contain microsatellite sequences and poly-(A) sequences as determined by a single pass manual sequencing. These 39 clones represent transcripts of 15 unique genes, six of which contain GA-repeats and nine CA-repeats. The microsatellites associated genes include proteins with regulatory functions such as cyclin B1, Y-box protein YB2, cyclin-dependent kinase 8 (cdk 8), and DNA excision repair protein MHR 23B. Other transcripts include growth hormone, ribosomal protein S16 and cytochrome C oxidase subunit 1. Eight of these genes harbor microsatellites at 5'-nontranslated regions (NTR), five at 3'-NTRs, and two in the coding regions. To determine polymorphism in these transcribed microsatellite loci, PCR primers were designed from flanking sequences. Genomic DNAs were amplified and analyzed. like non-transcribed microsatellites, high polymorphic rates were found with these transcribed microsatellites. These loci were also found to be mostly polymorphic in the Auburn resource families. Therefore, they should be useful for construction of catfish genetic linkage map and for mapping important QTLs in catfish.