Glutamine accumulation inhibits root growth and lateral root formation in ginseng hairy roots

A hundred and ninety-three hairy root lines were produced from Korea ginseng (P. ginseng). These hairy root lines were classified into five different types, depending on their phenotypes. Metabolic profiling by 1H NMR analysis indicated that the glutamine concentration was about five-fold higher in hairy root types with sluggish growth rates and low branching phenotypes than other hairy root types. Glutamine was detected at much higher levels in root tip zones when compared to those of root elongation zones. When the segments of the high branching hairy root were cultured in a medium containing more than 30 mM glutamine, root growth and lateral root formation were significantly reduced. It is known that nitrate is a major nitrogen source and can act as regulatory signal on the root development. In this study, we identify and suggest that glutamine plays an important role in root growth and phenotypes in ginseng hairy roots.