EST-library construction using spore RNA of the arbuscular mycorrhizal fungus Gigaspora rosea

RNA was extracted from activated spores of the arbuscular mycorrhizal fungus Gigaspora rosea. Double-stranded cDNA was synthesised, digested and cloned into the vector lambda-ZAP express. Of the 1,500 clones obtained, 1.5% carried inserts of the rRNA gene cluster. After excision, inserts from 50 randomly selected clones were sequenced. Database searches revealed that 62% of the clones had similarities to already known sequences. These mainly code for proteins involved in translation and protein processing, replication and the cell cycle and cell signal transduction. One fragment probably belonged to a metallothionein-encoding gene which may be involved in heavy-metal binding. The method presented is an easy and rapid way to obtain short fragments of coding regions for expressed sequence tag libraries.