Page 1 of 37 Physiologia Plantarum 1 2 3 The heterologous expression of a plastocyanin in the diatom 4 5 Phaeodactylum tricornutum improves cell growth under iron-deficient 6 7 conditions 8 9 10 11 12 Carmen Castell1, Pilar Bernal-Bayard1, José M. Ortega1, Mercedes Roncel1, Manuel Hervás1, José 13 14 A. Navarro1* 15 16 17 18 19 20 21 1Instituto de Bioquímica VegetalFor y PeerFotosíntesis, Review cicCartuja, Universidad de Sevilla and CSIC, 22 23 Seville, Spain. 24 25 26 27 28 29 30 31 32 *Corresponding author: José A. Navarro, Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de 33 34 Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla and CSIC, Américo Vespucio 35 36 49, 41092-Sevilla, Spain; E-mail:
[email protected] 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 1 Physiologia Plantarum Page 2 of 37 1 2 3 ABSTRACT 4 5 6 We have investigated if the heterologous expression in the diatom Phaeodactylum tricornutum 7 8 of a functional green alga plastocyanin, as an alternative to cytochrome c6 under iron-limiting 9 conditions, can improve photosynthetic activity and cell growth. Transformed P. tricornutum strains 10 11 were obtained expressing a single-mutant of the plastocyanin from the green algae Chlamydomonas 12 13 reinhardtii that had previously shown to be the more effective in reducing P. tricornutum 14 photosystem I in vitro. Our results indicate that even the relatively low intracellular concentrations of 15 16 holo-plastocyanin detected (≈4 µM) are enough to promote an increased growth (up to 60%) under 17 iron-deficient conditions as compared with the WT strain, measured as higher cell densities, content 18 19 in pigments and active photosystem I, global photosynthetic rates per cell and even cell volume.