Identification and characterization of putative conserved IAM-hydrolases in developing rice grains

Abstract

Indole-3-acetamide (IAM) pathway was proposed to produce indole-3-acetic acid (IAA). This pathway was proven to be functional in many species of bacteria and expected to operate in plants based on the identification of IAM and IAM-hydrolase (AMI) activity in certain plant species. Available putative AMI sequences from a wide array of monocot and dicot plants were identified and the phylogenetic tree was constructed and analyzed. We identified in this tree, a clade that contained sequences from species across the plant kingdom suggesting that AMI is conserved and may have a primary role in plant growth and development. This clade contained the isolated and well characterized Arabidopsis and Nicotiana AMIs. The preliminary reverse transcriptase polymerase chain reaction (RT-PCR) results for the conserved rice AMI (Os04G02780) showed a transcript for the gene encoded by this enzyme at 1, 7 and 21 days after anthesis (DAF) during the active period of IAA accumulation in developing grains. Based on the accumulated data, we suggested that sequences in this clade are conserved and have an important role in IAA synthesis or other primary processes in plant development. 

Key words: Auxin, indole-3-acetic acid, indole-3-acetamide, tryptophan, IAM-hydrolase.