Comparative and Developmental Analysis of Plastid-Targeted Proteins in Malus x domestica (Apple) and Higher Plants

Plastids actively participate in a wealth of plant processes critical to development, growth and adaptation to environmental stimuli. Fruit plastids maintain diverse morphologies and internal structures which undergo dynamic transitions throughout fruit development. Only about 40% of the 10,492 putative apple plastid-targeted proteins retain a homolog with the Arabidopsis thaliana plastid-targeted proteome and ~57% with the entire Arabidopsis proteome. Co-expression analysis of 2,224 apple genes encoding predicted plastid-targeted proteins identified nine significant expression profiles throughout apple fruit development. Further, a comparative analysis of Arabidopsis, Prunus persica (Peach), Malus × domestica (Apple), Populus trichocarpa (Black cottonwood), Fragaria vesca (Woodland Strawberry), Solanum lycopersicum (Tomato) and Vitis vinifera (Grapevine) also identified a large number of species-specific plastid-targeted proteins, indicating the presence of unique plastid processes in each species.  Furthering the knowledge of plastid-targeted proteins will aid in understanding differing roles of plastids throughout development as well as species-specific roles of plastids across plant species.