Polyamine Levels, Arginine and Ornithine Decarboxylase Activity in Embryogenic Cultures of Araucaria angustifolia (Bert.) O. Kuntze

摘要

Somatic embryogenesis (SE) is a useful tool for mass clonal propagation and ex situ conservation of commercial and endangered plant species, especially conifers. However, this micropropagation technique has also been used as source of material for studies of plant cell developmental processes, using comparative biochemical, physiological and molecular similarities between zygotic and somatic embryo development. Polyamines (PAs), specifically putrescine (Put), spermidine (Spd), spermine (Spm) and cadaverine (Cad) have demonstrated a fundamental role during seed formation and development of somatic embryos. In A. angustifolia, previous studies demonstrated that PAs can efficiently modulate early-somatic embryo formation, and its levels can be used asbiochemical markers for selection of highly responsive embryogenic cultures. Despite this potential use in SE, the PAs biosynthesis pathways in this system are still unknown. In this work we analyse the activity of two enzymes related to Put biosynthesis, arginine decarboxylase (ADC) and ornithine decarboxylase (ODC), in two A. angustifolia lines with different embryogenic potential: responsive EC line (R) or blocked EC line (B). For both cell lines, free Put was the main PA recorded followed by Spd andSpm. Comparatively, cell line B showed lower levels of Put for free and conjugated forms. In addition, Cad was the main PA accumulated for cell line B in the PCA insoluble fraction followed by Put, Spd, and Spm. The Put/(Spd+Spm) ratio was higher in cell line R, observed in all fraction analyzed (free, conjugated, and PCA insoluble fraction). Significant differences between ADC and ODC activities, in both cell lines were not detected. In this work, free and conjugated Put profile did not correlate with recorded levels of ADC and ODC activity. Cell lines of A. angustifolia did not show a preferentially route (ADC or ODC) for Put biosynthesis, suggesting that polyamines metabolism may also diverge from other conifers.