title: Increased zinc content in transplastomic tobacco plants expressing a polyhistidine-tagged Rubisco large subunit.
abstract: Rubisco is a hexadecameric enzyme composed of two subunits: a small subunit (SSU) encoded by a nuclear gene (rbcS), and a large subunit (LSU) encoded by a plastid gene (rbcL). Due to its high abundance, Rubisco represents an interesting target to express peptides or small proteins as fusion products at high levels. In an attempt to modify the plant metal content, a polyhistidine sequence was fused to Rubisco, the most abundant protein of plants. Plastid transformation was used to express a polyhistidine (6x) fused to the C-terminal extremity of the tobacco LSU. Transplastomic tobacco plants were generated by cotransformation of polyethylene glycol-treated protoplasts using two vectors: one containing the 16SrDNA marker gene, conferring spectinomycin resistance, and the other the polyhistidine-tagged rbcL gene. Homoplasmic plants containing L8-(His)6S8 as a single enzyme species were obtained. These plants contained normal Rubisco amounts and activity and displayed normal photosynthetic properties and growth. Interestingly, transplastomic plants accumulated higher zinc amounts than the wild-type when grown on zinc-enriched media. The highest zinc increase observed exceeded the estimated chelating ability of the polyhistidine sequence, indicating a perturbation in intracellular zinc homeostasis. We discuss the possibility of using Rubisco to express foreign peptides as fusion products and to confer new properties to higher plants.
authors.affiliation: CEA Cadarache, Direction des Sciences du Vivant, Département d'Ecophysiologie Végétale et de Microbiologie, Unité Mixte de Recherche 6191 CNRS-CEA-Université de la Méditerranée, France. dominique.rumeau@cea.fr
authors.forename: Dominique
authors.initials: D
authors.lastname: Rumeau
authors.forename: Noëlle
authors.initials: N
authors.lastname: Bécuwe-Linka
authors.forename: Audrey
authors.initials: A
authors.lastname: Beyly
authors.forename: Patrick
authors.initials: P
authors.lastname: Carrier
authors.forename: Stéphan
authors.initials: S
authors.lastname: Cuiné
authors.forename: Bernard
authors.initials: B
authors.lastname: Genty
authors.forename: Peter
authors.initials: P
authors.lastname: Medgyesy
authors.forename: Eva
authors.initials: E
authors.lastname: Horvath
authors.forename: Gilles
authors.initials: G
authors.lastname: Peltier