Overexpression of cphA gene from Nostoc flagelliforme improves the drought tolerance of Arabidopsis thaliana

Abstract

Nostoc flagelliforme is a terrestrial cyanobacterium distributed in arid or semiarid steppes in western and northwestern China. Cyanophycin is synthesized by cyanophycin synthetase (CphA), which serves as a storage polymer for nitrogen, carbon, and energy in N. flagelliforme. In the present study, cphA (GenBank Accession No.: KX469292), an open reading frame (ORF) of 2706 bp encoding a protein of 901 amino acid residues, was cloned. We found that cyanophycin synthesis was promoted by the expression of cphA in E. coli. The function of the cphA gene in Arabidopsis thaliana under drought stress was investigated, and stable integration and expression of transgenes in transgenic lines were confirmed by PCR, Western blot, Southern blot, and real-time PCR analyses. The transcript abundance of cphA was markedly increased in transgenic A. thaliana compared with that in the untransformed plants. A subcellular localization assay confirmed that cphA protein was targeted to the cytoplasm. The survival rate was also significantly higher in cphA overexpression lines than that in untransformed plants under drought stress, which verified by drought tolerance assay of the transgenic plants. These findings highlight the potential importance of cphA in the drought tolerance of N. flagelliforme.