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 P-SEE1::IPT) or to the beta-glucuronidase reporter gene UIDA (P-SEE1::UIDA). Plants were regenerated under selection for the HPH hygromycin resistance gene in the vector. P-SEE1::UIDA transformants confirmed that the SEE1 flanking sequence functioned as a senescence-enhanced promoter in ryegrass. The IPT transgene was detected in 28 regenerants (P-SEE1::IPT) from five independent transformation events. P-SEE1::IPT leaves displayed a stay-green phenotype. Some P-SEE1::IPT lines developed spontaneous lesions.