Characterization of four extensin genes in Arabidopsis thaliana by differential gene expression under stress and non-stress conditions

From Arabidopsis thaliana we isolated four different cDNAs that encode extensins, a family of cell-wall hydroxyproline-rich glycoproteins (HRGPs). Putative proteins (AtExt2-5) contained one open reading frame and characteristic Ser-(Pro)4 sequences organized in a high-order repetitive motif. AtExt2-5 genes were strongly expressed during rehydration after dehydration. They were also expressed after treatment with various amino acids. In particular, AtExt3 and five mRNAs were abundantly accumulated after treatment with L-Ser, Hyp, and L-Pro, which are major components of extensin proteins. The AtExt transcripts were strongly expressed in root tissues of both unbolted and bolted plants. The transcripts of AtExt2, 3, and 5 were also detected in the lower stem and flower buds, and that of AtExt4 was detected in bolted flowers. Therefore, we suggest that these four AtExt genes are novel extensin genes in A. thaliana, because the expression of atExt1, which has already been isolated from A. thaliana, was different from these.