Enhanced production of recombinant human gastric lipase in turnip hairy roots

Abstract

Treatment with 2,4-D induced the development of callus-like structures on Brassica rapa hairy roots grown in liquid medium. The structures probably originated from pericycle cell divisions and developed in a non-concentric manner to give conical organs, which did not separate from the roots, whereas the root cortical and epidermal cell layers degenerated. Various cell types were found within the structures, indicating that these differ from simple calli. They are likely to represent secondary root primordia that fail to elongate as a result of hormonal pressure. Hairy roots transformed with a human gene encoding gastric lipase (hGL) were used to produce the recombinant protein. Lipase activity was measured in the culture medium of these roots. The analysis of N-glycans on hGL produced by hairy roots revealed the presence of paucimannosidic N-glycans. Moreover, when the root cultures were treated with 2,4-D, approximately 2.7 times more lipase activity was measured in the culture medium, compared to untreated root cultures, revealing the higher efficiency of this system for the production of a heterologous protein. In addition, some His-tag epitope was found on EGFP in the medium of 2,4-D-treated roots expressing a his-egfp gene, whereas the same tag was totally degraded in the medium of untreated roots, suggesting a reducing effect of 2,4-D on the release of proteolytic activity in the culture medium. We propose to name this new hairy root-derived protein production process “rhizocalli”.