Analysis of Proteins in Developing Style and Ovary with Reference to Self-Incompatibility of Japanese Pear

Abstract

The present paper deals with changes in proteins in the developing style and ovary of Japanese pear cv. Chojuro (Pyrus serotina Rehd.) to see if a relationship exists between protein composition and overcoming self-incompatibility following bud pollination. Results obtained are as follows;
1. In the immature excised-styles that can overcome self-incompatibility by bud pollination, incompatible pollen tubes grew similarly with compatible ones; while a clear distinction could be observed between compatible and incompatible growth of pollen tubes in the mature excised-styles.
2. The analysis of proteins in the styles by isoelectricfocusing polyacrylamide gel electrophoresis (IEF-PAGE) showed two unique bands which began to increase 4 days before anthesis; those which existed only in the style but not in other flower tissues such as ovary, petal, calyx, anther and peduncle. The PI values of the proteins were 6.0 and 6.1, respectively, both of which were glycoproteins.
3. According to sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), two new protein bands were also detected in the developing style. These bands appeared 4 days before anthesis and increased thereafter. Molecular weights of these proteins were about 5.2×10⁴ and 5.8×10⁴, respectively.
The floral stage when the new proteins were detected in styles by both IEF- and SDS-PAGE corresponded well with the stage the style began to possess strong self-incompatibility.