ACTIVITIES OF CAMV 35S AND NOS PROMOTERS IN POLLEN - IMPLICATIONS FORFIELD RELEASE OF TRANSGENIC PLANTS

The expression of foreign genes in pollen may pose potential problems in the field release of transgenic plants, since pollen represents a r oute whereby foreign genes and their products may escape into the wide r environment. The possible risks posed by crosshybridization with wil d relatives have been extensively explored, but problems that may aris e due to the expression of foreign gene products in pollen have not be en so widely studied. The activities of the CaMV 35S and nos promoters in pollen in populations of stably transformed plants and in transien t expression analysis are described. These promoters are commonly used in all areas of plant molecular biology research and their expression patterns will be of interest to those involved in field release studi es, The results show that both promoters had no detectable pollen acti vity in Arabidopsis, but both showed activity in tobacco pollen, The C aMV 35S-gus gene fusion showed heritable expression levels in tobacco pollen of up to a maximum of 64.6 pmol 4-MU min(-1) mg(-1) total prote in, nos promoter activity in transgenic tobacco pollen was highly vari able, with GUS activities ranging from undetectable levels up to 2561 pmol 4-MU min(-1) mg(-1) total protein within the transgenic populatio n. Histochemical staining of anther sections from 10-12 mm buds reveal ed that the CaMV 35S promoter had some activity in the vascular bundle , stomium and tapetum, while GUS expression from the nos promoter in s porophytic tissues was confined entirely to the stomium.