Histomorphology and proteomics during rooting of in vitro shoots in Cariniana legalis (Lecythidaceae), a difficult-to-root endangered species from the Brazilian Atlantic Forest

Abstract

Rooting is an important step of in vitro propagation that involves auxin signaling and the growth-promoting properties of phenolic compounds. We evaluated the effects of indole-3-butyric acid (IBA) and phloroglucinol (PG) on the in vitro rooting of shoots, histomorphology and proteomic profile during the root development in Cariniana legalis. Micropropagated shoots were incubated in 1/4 Murashige and Skoog culture medium supplemented with IBA (0, 50 and 100 μM) and PG (0 and 30 μM). The root development, histomorphology and proteomic profile were analyzed. IBA was necessary for root induction and the combination of IBA (50 or 100 μM) with 30 μM PG significantly increased the number of roots. The histomorphology of shoots treated with 50 μM IBA + 30 μM PG showed that rooting started at 12 days of induction, with the presence of meristematic-type cells from the callus induced on the base of shoots. The 50 μM IBA + 30 μM PG (IBA + PG) treatment affected the abundance of proteins during the rooting of shoots. The up-accumulation of proteins related to carbohydrate and amino acid metabolic processes in 12-day IBA + PG-treated shoots compared with 0-day shoots (before root induction) was associated with the rooting promoted by IBA + PG. The down-accumulation of proteins involved in secondary metabolic processes in 12-day IBA + PG-treated shoots compared with 12-day with no plant growth regulators (PGR) shoots was related to the lack of rooting in with no PGR shoots, while the increased accumulation of antioxidant proteins was related to rooting in 12-day IBA + PG-treated shoots compared with no PGR shoots. This is the first work to demonstrate the effect of IBA + PG on the proteomic profile and histomorphology during the rooting of an economically and ecologically important endangered species, which is difficult to root in vitro. Indole-3-butyric acid improved the in vitro rooting changing the proteomic profile and histomorphology in micropropagated shoot of Cariniana legalis, an endangered species from Atlantic Forest, which is difficult-to-root.