Comparison of abp1 primary sequences from monocotyledonous and dicotyledonous species

The cDNA fragments of auxin-binding protein (ABP1) were isolated by degenerated-primer mediated reverse transcription-polymerase chain reaction (RT-PCR) from dicotyledonous plant species, i.e. cress, mung bean, pea, radish and soybean, and monocotyledonous species, i.e, oat and rice. Cloned abp1 cDNA fragments were sequenced and compared with known abp1 clones from A. thaliana, maize, strawberry and tobacco at the amino acid level. In all plant species studied, the amino acid sequences of newly isolated abp1 clones were highly conserved at two regions (region A: Thr-Pro-Ile-His-Arg-His-Ser-Cys-Glu-Glu-Ile/Val-Phe-Ile /Thr/Val-Val-Leu/Pro/Val-Lys-Gly-Xaa-Gly-Thr-Leu/Val; region B: His-Glu-Asp-Leu-Gln-Phe/Val-Leu-Asp/Val-Ile/Val-Ile-Ser-Arg-Pro-Pro), which were previously reported to be important for auxin-binding. On the other hand, some putative residues of amino acids in the region between regions A and B could be found to be specific in dicot and monocot species, respectively. Southern-blot analysis indicated a small abp1 gene family in all species studied. Northern-blot analysis indicated that the size of abp1 mRNA transcripts in all species studied was conserved at approximately 850 bp. The phylogenetic tree of ABP1 was analyzed by the UPGMA method.