Introduction and differential use of various promoters in pollen grains of Nicotiana glutinosa and Lilium longiflorum

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Abstract
As part of our research to develop an alternative system for the transformation of recalcitrant plant species we investigated the use of the male gametophyte as a transformation vector. Therefore the activity of four different promoters (CaMV 35S, LAT52, chiA PA2 and TR2') was analyzed in pollen of a dicot (Nicotiana glutinosa) and a monocot (Lilium longiflorum) plant species. Gene constructs in which the ß-glucuronidase (GUS) gene was placed under the control of these promoters were introduced in pollen using a particle delivery system. No activity of the Cauliflower Mosaic Virus (CaMV) 35S promoter was detected in pollen of both N. glutinosa and L. longiflorum. The promoter of the tomato flower-specific LAT52 gene was highly active in N. glutinosa pollen but remained silent in L. longiflorum pollen. A similar expression pattern was observed for the pollen-specific Chalcone Flavanone Isomerase chiA PA2 promoter originally isolated from petunia. The TR2′ mannopine synthase promoter of Agrobacterium tumefaciens, however, was active in pollen from Solanaceous species and also in pollen from the monocot L. longiflorum. This suggests that the TR2' promoter is active in vegetative and sporogenous tissues of dicot and monocot plant species.