Modification of senescence in ryegrass transformed with IPT under the control of a monocot senescence-enhanced promoter

We report here the genetic modification of ryegrass senescence. Embryogenic cell suspensions of Lolium multiflorum were transformed by microprojectile bombardment with plasmid constructs containing 1.98 kb of the 5 flanking sequence of SEE1 (a maize cysteine protease gene showing enhanced expression during senescence) fused either to the Agrobacterium tumefaciens cytokinin biosynthesis gene IPT (designated PSEE1::IPT) or to the -glucuronidase reporter gene UIDA (PSEE1::UIDA). Plants were regenerated under selection for the HPH hygromycin resistance gene in the vector. PSEE1::UIDA transformants confirmed that the SEE1 flanking sequence functioned as a senescence-enhanced promoter in ryegrass. The IPT transgene was detected in 28 regenerants (PSEE1::IPT) from five independent transformation events. PSEE1::IPT leaves displayed a stay-green phenotype. Some PSEE1::IPT lines developed spontaneous lesions.