Phylogenetic relationships, gene structures, and motif composition of Hsp90 genes in A . thaliana (At), P . trichocarpa (Pt), and O . sativa (Os). A. A multiple alignment of full-length Hsp90 protein sequences from three species was executed using Clustal X2.1 and a phylogenetic tree was constructed using MEGA 4.0 by the neighbor-joining (NJ) method with 1000 bootstrap replicates. Bootstrap support is indicated at each node. The two major groups are marked with different background colors. B. Exon/intron structures of the Hsp90 genes. Green boxes represent exons and black lines represent introns. The numbers indicate the splicing phases of the Hsp90 genes: 0, phase 0; 1, phase 1; and 2, phase 2. C. Schematic representation of conserved motifs (obtained using MEME) in Hsp90 proteins. Different motifs are represented by boxes of different colors. Details of the individual motifs are shown in Additional file 5.