Enolase, a cadmium resistance related protein from hyperaccumulator plant Phytolacca americana, increase the tolerance of Escherichia coli to cadmium stress

NOVELTY STATEMENT The expression of the Cd resistance related protein PaENO can significantly increase the tolerance of E. coli to Cd, which was achieved by reducing the content of Cd in E. coli cells, and was independent of the enzymatic activity of PaENO. Moreover, PaENO may be alternatively translated into the transcription factor PaMBP-1 to participate in the response of P. americana to Cd stress. Phytolacca americana is a Cd hyperaccumulator plant that accumulates significant amounts of Cd in leaves, making it a valuable phytoremediation plant species. Our previous research found enolase (ENO) may play an important part in P. americana to cope with Cd stress. As a multifunctional enzyme, ENO was involved not only in glycolysis but also in the response of plants to various environmental stresses. However, there are few studies on the function of PaENO (P. americana enolase) in coping with Cd stress. In this study, the PaENO gene was isolated from P. americana, and the expression level of PaENO gene significantly increased after Cd treatment. The enzymatic activity analysis showed PaENO had typical ENO activity, and the 42-position serine was essential to the enzymatic activity of PaENO. The Cd resistance assay indicated the expression of PaENO remarkably enhanced the resistance of E. coli to Cd, which was achieved by reducing the Cd content in E. coli. Moreover, both the expression of inactive PaENO and PaMBP-1 (alternative translation product of PaENO) can improve the tolerance of E. coli to Cd. The results indicated PaENO may be alternatively translated into the transcription factor PaMBP-1 to participate in the response of P. americana to Cd stress.