Cloning, characterization and expression analysis of a sucrose synthase gene from tropical epiphytic orchid Oncidium Goldiana

Abstract

A full-length cDNA encoding sucrose syntbase was isolated from the tropical epiphytic orchid Oncidium Goldiana. The cDNA is 2829 bp in length containing an open reading frame of 2447 bp encoding 816 amino acids with a predicted molecular mass of 93.1kDa. The deduced amino acid sequence of O. Goldiana sucrose synthase (Osus) shares more than 80% identity with those from other monocotyledonous plants. The sucrose synthase gene was demonstrated to encode a functional sucrose synthase protein by expression as recombinant protein in Escherichia coli. The Osus mRNA is present in all the tissues analysed, with the highest levels in strong sinks such as developing inflorescence and root tips. Incubation with sucrose or glucose resulted in a significant increase in the steady-state Osus mRNA levels in root tips and mature leaves in a similar pattern to maize Sus1. Expression of the Osus mRNA in mature leaves was markedly enhanced by anaerobic conditions and elevated CO2. The expression pattern and regulation of the gene suggest that the sucrose synthase plays an important role in the growth and development of the tropical epiphytic orchid O. Goldiana.