Simultaneous Expression of Spinacia oleracea Chloroplast Choline Monooxygenase (CMO) and Betaine Aldehyde Dehydrogenase (BADH) Genes Contribute to Dwarfism in Transgenic Lolium perenne

Choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH) catalyze the first and second steps in the biosynthesis of glycine betaine in betaine-accumulating plants. Over-expression of the Spinacia oleracea chloroplast choline monooxygenase (SoCMO) and betaine aldehyde dehydrogenase (SoBADH) genes has not been reported in Lolium perenne. In this investigation, the SoCMO and SoBADH genes have been used to generate transgenic L. perenne plants via particle bombardment. Transgenic plants have been confirmed with PCR, Southern blot, and Northern blot analyses. Enhanced salt stress tolerance has been observed from SoBADH–SoCMO transgenic L. perenne plants. The dwarf phenotype was first observed 3 months after transgenic plants were established in soil and was to be stably inherited. Height of transgenic plants was decreased by 63% compared to the control. Measurement of endogenous GAs content demonstrated that the content of endogenous GA1 was decreased by 75.2%, and the content of endogenous GA4, GA12, GA19, and GA53 of transgenic plants was increased by 200%, 221%, 105%, and 108%, respectively, compared to the control plants. Dwarf trait of SoBADH–SoCMO transgenic L. perenne plants can be recovered by application of exogenous GAs. These results demonstrated that simultaneous expression of the SoCMO and SoBADH genes enhanced salt stress tolerance and induced dwarfism in transgenic L. perenne. Dwarfism induced by expression of the SoCMO and SoBADH genes was associated with synthesis of endogenous GAs and it could be recovered by application of exogenous GAs. This is the first report on dwarfism induced by expression of the SoCMO and SoBADH genes in a species in turfgrass.