Proteomic profiles during adventitious rooting of Eucalyptus species relevant to the cellulose industry

Adventitious rooting (AR) is an obligatory step for vegetative propagation of commercial woody species. Paper industries have interest in Eucalyptus globulus Labill and its hybrids due to low lignin and lipid contents, which facilitate cellulose extraction. However, this species and some of its hybrids are recalcitrant to rooting, often requiring exogenous auxin supply. Here we performed a comparative analysis of proteome changes during AR of E. globulus and the easy-to-root species Eucalyptus grandis W. Hill and the effects of exogenous auxin in different phases of the process (induction and formation), using a label-free quantification method. We identified 398 differentially abundant proteins, which were predicted to be involved in different biological pathways, mainly oxidative stress, energy metabolism and photosynthesis. Notable differences between species included proteins involved in oxidative stress, carbon and secondary metabolism. Exogenous auxin appeared to affect the availability of carbon sources and other phytohormones, besides cell cycle and microtubule-related proteins. Important players were also identified in each phase of AR. This is the first in depth analysis of protein changes during AR in Eucalyptus. The findings can be used in future studies to evaluate rooting competence in different genotypes and provide leads for AR improvement.