The present invention is directed to a method for expression of at least one heterologous gene in a host cell comprising transforming a host cell with at least one nucleic acid construct comprising a complete &agr; subunit of an RNA polymerase or a portion thereof of a hybrid nucleic acid containing a portion of the &agr; subunit of an RNA polymerase obtained from the same genus as the heterologous gene, and transforming the host cell, with at least one heterologous gene; and culturing the transformed host cell. The present invention further is directed to nucleic acid molecules used in the present method, vectors containing these nucleic acid molecules, and host cells containing the nucleic acid molecules. The nucleic acid encoding the &agr; subunit of an Agrobacterium RNA polymerase and the corresponding amino acid sequence and portions thereof is disclosed.
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