Cyanobiont diversity within coralloid roots of selected cycad species

The diversity and host specificity of the cyanobionts of several cycad spec ies (Cycas circinalis L., C. rumphii Miq., Encephalartos lebomboensis I. Ve rd., E. villosus Lem., and Zamia pumila L.) collected in a botanical garden were examined using the tRNA(Leu)(UAA) intron sequence as a genetic marker . Nested PCR was used to specifically amplify the tRNA(Leu)(UAA) intron dir ectly from the freshly isolated symbiotic cyanobionts. By direct amplificat ion of the biological material the laborious isolation of the cyanobionts c an be avoided. A single DNA fragment, ranging in size from 287 bp to 329 bp , was consistently amplified from the different biological samples. The int ron sequences obtained from the cycad cyanobionts show high similarities to the corresponding sequences in the free-living strains Nostoc sp. strain P CC 73102 and N. muscorum as well as in several lichen cyanobionts. Although different Nostoc strains were found in the present study, no sequence vari ation was observed when analyzing a single coralloid root. However, differe nt coralloid roots from a single cycad individual may harbor different cyan obacteria. Moreover, cyanobionts in coralloid roots of both Encephalartos l ebomboensis and E. villosus were found to possess the same intron sequence. (C) 1999 Federation of European Microbiological Societies. Published by El sevier Science B.V. All rights reserved.