Cloning and characterization of ACC oxidase genes from tulip

Abstract

Five cDNA clones encoding 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) were isolated from tulip (Tulipa gesneriana L.) by differential screening of the petal cDNA library and were designated as TgACO1, TgACO2, TgACO3, TgACO4 and TgACO5. The deduced amino acid sequences exhibited similarity to ACO proteins from other plant species. Among these proteins, TgACO1-4 have high similarity (90–94% identity) each other, whereas TgACO5 showed low similarity compared with the other four proteins (50% identity). Phylogenic analysis indicated that TgACO1-4 and TgACO5 are distant. Genomic analysis of TgACO1-4 showed that they are organized into four exons and three introns, whereas TgACO5 consists of three exons interrupted by two introns. Real-time RT-PCR analysis of gene expression revealed that TgACO1, TgACO3 and TgACO5 were expressed in wilting petals, leaves, and stems, respectively, whereas TgACO2 and TgACO4 were expressed only at basal levels in these tissues. Therefore, tulip ACO genes seem to be regulated differentially among the vegetative tissues and during flower senescence.