Involvement of differentially accumulated proteins and endogenous auxin in adventitious root formation in micropropagated shoot cuttings of Cedrela fissilis Vellozo (Meliaceae)

Investigation of the biochemical and molecular changes during rooting in woody species can reveal how specific molecules are involved in adventitious root (AR) induction. We investigated the effects of indole butyric acid (IBA) and inhibitors of polar auxin transport and auxin signaling on ex vitro rooting of micropropagated shoots of Cedrela fissilis and evaluated the proteomic profile and endogenous contents of indole acetic acid (IAA) during AR initiation. We observed that exogenous IBA was not necessary for ex vitro rooting, and root induction was significantly reduced by auxin signaling (p-chlorophenoxyisobutyric acid—PCIB) and polar auxin transport (triiodobenzoic acid—TIBA) inhibitors. The presence of meristematic cells and the formation of meristematic centers in the base of shoot cuttings at 3 days of rooting are necessary for AR formation. The accumulation of cell division- and auxin-related proteins and the presence of unique proteins related to cell wall modification in shoot cuttings at 3 days of rooting were associated with higher IAA contents and AR initiation. In addition, an accumulation of proteins related to dephosphorylation, glycolytic and tricarboxylic acid cycle pathways and a reduction in the accumulation of proteins from isoflavonoid metabolism were associated with the promotion of AR initiation. These results show the relevance of these proteins for AR initiation in this species. This is the first study showing the involvement of protein accumulation and endogenous IAA contents in adventitious rooting initiation in C. fissilis, an easily rooted endangered woody species from the Brazilian rainforest.