RESUMEN
Filamentation temperature-sensitive H (FtsH) is an ATP-dependent metalloprotease in prokaryotes and eukaryotes. Homology-based analysis was applied to determine 12 ftsH genes in Arabidopsis genome and 9 members in rice genome. Distribution of these ftsH genes on each chromosome displayed a clear preference for some chromosomes such as chromosome 1, 2, 5 of Arabidopsis and chromosome 1,5 of rice. All 21 FtsH proteins were subcellularly targeted to chloroplast or mitochondria. These members could be phylogenetically assorted as eight groups, of which no ortholog of AtFtsH12 in rice was detected. Paralogs in each group shared similarity higher than 80% and orthologs higher than 70%. This strongly indicated that the members from single group were descended from a common ancestral gene. Four pairs of paralogs, AtftsH1/5, AtftsH2/8, AtftsH7/9 and AftsH3/10 were found in Arabidopsis genome. However, only two pairs of ftsH paralogs, OsftsH3/8 and OsftsH4/5, resided in rice genome. The highly homologous members in each group performed striking conservation of exon-intron boundaries and preference for the variable residues in function domains. By contrast, there was significant difference in base composition and sequence length of introns. The comparative analysis of the ftsH gene families of Arabidopsis and rice provided the basis for characteristic and function research of ftsH genes in other plants.