Oak protein profile alterations upon root colonization by an ectomycorrhizal fungus

Abstract

An increased knowledge on the real impacts of ectomycorrhizal symbiosis in forest 32 species is needed to optimize forest sustainable productivity and thus to improve forests 33 services and their capacity to act as carbon sinks. In this study we investigated the 34 response of an oak species to ectomycorrhizae formation using a proteomics approach 35 complemented by biochemical analysis of carbohydrates levels. Comparative proteome 36 analysis between mycorrhizal and non-mycorrhizal cork oak plants revealed no 37 differences at the foliar level. However, the protein profile of 34 unique oak proteins 38 was altered in the roots. Consistent with the results of the biochemical analysis, the 39 proteome analysis of the mycorrhizal roots suggests a decreasing utilization of sucrose 40 for the metabolic activity of mycorrhizal roots which is consistent with an increased 41 allocation of carbohydrates from the plant to the fungus in order to sustain the 42 symbiosis. In addition, a promotion of protein unfolding mechanisms, attenuation of 43 defense reactions, increased nutrient mobilization from the plant-fungus interface (N 44 and P), as well as cytoskeleton rearrangements and induction of plant cell wall 45 loosening for fungal root accommodation in colonized roots, are also suggested by the 46 results. The suggested improvement in root capacity to take up nutrients accompanied 47 by an increase of root biomass without apparent changes in aboveground biomass 48 strongly re-enforce the potential of mycorrizal inoculation to improve cork oak forest 49 resistance capacity to cope with coming climate change.