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

Abstract.

Based on the relative ease of performing targeted 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 region of the gene for the sugar beet (Beta vulgaris) V-type H⁺-ATPase subunit isoform c. Four gene knockout constructs were tested in which the neomycin phosphotransferase 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 sufficiently high to generate large numbers of stable transgenic plants. The numbers of plants obtained with the two V-type H⁺-ATPase promoter fragments were comparable 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.