Light spectrum and explant type drive hormonal and proteomic reprogramming in micropropagation of the endangered Paubrasilia echinata

Paubrasilia echinata is an endangered and emblematic tree species of the Brazilian Atlantic Forest, requiring efficient biotechnological strategies for its conservation. This study aimed to establish optimal conditions for in vitro propagation of P. echinata by evaluating the effects of explant type and light spectrum on shoot development, as well as to characterize the biochemical and proteomic alterations associated with shoot development. Cotyledonary nodal segments incubated under light-emitting diode (LED) lamp with a combined light spectrum of white, medium blue, deep red, and far-red (W/mB/dR/fR) exhibited the greatest shoot elongation and biomass accumulation. The LED W/mB/dR/fR lamp induced distinct metabolic reprogramming associated with shoot development, leading to increased endogenous levels of benzyladenine, abscisic acid, and putrescine. Furthermore, enhanced shoot growth under LED W/mB/dR/fR was associated with the up-accumulation of proteins involved in photosynthesis (oxygen-evolving enhancer protein 1), redox homeostasis (ascorbate peroxidase and peroxidases), cellular stability (heat shock proteins), and cytoskeletal organization (tubulin). Ex vitro rooting ranged from 50–65% and was not significantly influenced by explant type or indole-3-butyric acid concentration. Overall, these findings establish a physiologically supported micropropagation protocol for large-scale production of P. echinata, providing a strategic tool for the conservation of this culturally and ecologically Brazilian species.