Hairy roots, callus, and mature plants of Arabidopsis thaliana exhibit distinct glucosinolate and gene expression profiles

Abstract

Hairy root cultures transformed with Agrobacterium rhizogenes or undifferentiated callus cultures are used for production of plant secondary metabolites. Glucosinolates (GS) are a group of secondary metabolites that produce a variety of bioactive compounds upon hydrolysis. Several studies report the successful production of high concentrations of secondary metabolites in vitro. However, such cultivation methods can significantly change metabolic profiles, and the mechanism behind this to be rarely understood. Therefore, we compared the GS and transcript profiles of Arabidopsis thaliana leaves and roots with hairy root and callus in vitro cultures. Compared to the roots of intact A. thaliana plants, overall, hairy roots contained lower GS levels. In particular, lower quantities of short-chain aliphatic GS were observed and a larger proportion of long-chain aliphatic GS on total content. Corresponding, the transcript levels of most aliphatic biosynthetic genes (MAM1, CYP79F1, CYP83A1, UGT74C1, and SUR1) were significantly lower in hairy root cultures compared to roots of intact plants. In callus culture, the lowest transcripts levels were detected for overall GS biosynthetic genes with an absence of aliphatic GS. From the indole group, 1-methoxy-indol-3-ylmethyl GS was found to be a major component in hairy root cultures and roots whereas indol-3-ylmethyl GS dominated in leaves and 4-hydroxy-indol-3-ylmethyl GS in callus cultures. Leaves of intact plants contained the highest amounts of GS. Here, aliphatic short-chain GS dominated which was in accordance with transcript levels of aliphatic biosynthetic genes. The study reveals tissue-specific accumulation of GS and transcript pattern in plants distinct from in vitro culture systems.