Promoter subfragments of the sugar beet V-type H + -ATPase subunit c isoform drive the expression of transgenes in the moss Physcomitrella patens

Based on the relative ease of performing tar- geted nuclear gene knockout, the moss Physcomitrella patens has recently been developed as a model system for plant functional genomics. To address the need for new promoters that could drive expression of transgenes in this moss, we tested two fragments of the promoter re- gion of the gene for the sugar beet (Beta vulgaris) V-type H + -ATPase subunit isoform c. Four gene knockout con- structs were tested in which the neomycin phosphotrans- ferase II selection marker gene was put under the control of two distinct V-type H + -ATPase promoter fragments, the NOS promoter, or the CaMV 35S promoter. In each case the selection cassettes were flanked by moss FtsZ1 cDNA sequences to facilitate chromosomal targeting. From a total of more than 440 transformed plants, the number of plants generated per construct was monitored and found to be in the range of 5 to 11 stable transgenics per transformation. Both V-type H+-ATPase promoter fragments lead to NPTII expression levels that were suf- ficiently high to generate large numbers of stable trans- genic plants. The numbers of plants obtained with the two V-type H + -ATPase promoter fragments were compa- rable to those with constructs containing the standard NOS and 35S promoters. We propose that the higher plant V-type H+-ATPase promoter can be used for the expression of transgenes in the bryophyte P. patens.