Cloning and expression analysis of a dirigent protein gene from the resurrection plant Boea hygrometrica

Resurrection plants are tolerant to extreme dehydration and are useful model systems to study genes that play a role in drought tolerance. A gene fragment encoding a dirigent protein that is predicted to function in lignin biosynthesis was identified from leaves of the resurrection plant Boea hygrometrica via cDNA microarray screening. A cDNA, designated BhDIR1, containing the complete predicted open reading frame, was obtained by 5′-RACE. BhDIR1 transcripts were found to be accumulated in response to changes in plant dehydration status, exogenously applied phytohormones and signaling molecules, and temperature stresses. BhDIR1 encodes a protein of 199 amino acids, which shows 20–40% similarity to dirigent proteins reported from other plants. BhDIR1 is predicted to contain a cleavable signal peptide at the N-terminal, and its plasma membrane/cell wall localization was confirmed using a GFP fusion protein assay. Consistent with this discovery, the acid-soluble lignin content decreased in dehydrated B. hygrometrica leaves. Taken together, our results indicate a protective role for a dirigent protein in response to drought stress by changing the physical characters of lignin which in turn is predicted to affect the mechanical strength and flexibility of the plant cell wall.