Tissue-specific expression of divergent actins in soybean root

Abstract

It has been proposed that the evolution of distinct classes of genes encoding the κ-, λ-, and μ-actins in soybean is the result of an ancient divergence in patterns of actin gene expression. In this study, antisera against a family of synthetic actin peptides from a divergent region within the predicted actin polypeptide sequences have been used to explore the differential expression of plant actins. Antiserum elicited against a 16-residue synthetic λ-actin peptide SAc4:257 reacted with a 46-kilodalton protein in soybean extracts, showed specificity for the λ-peptide over the divergent κ- and μ-actin peptides in enzyme-linked immunosorbent assays, and reacted strongly and preferentially with root protoderm in apical roots and in lateral root primordia. Antiserum elicited against the synthetic κ-actin peptide SAc1:257 reacted with 46-kilodalton protein on protein gel blots, showed partial specificity toward the immunogenic λ-peptide over the divergent λ- and μ-peptides, and reacted strongly with all root tissues with the exception of root cap. These data support the hypothesis that ancient classes of plant actin genes may have been preserved because of their role in developmentally controlled differences in tissue-specific actin expression and/ or function. The possibility that other diverse actin classes have unique patterns of regulation is discussed.