Abscisic acid-induced secretory proteins in suspension-cultured cells of winter wheat.

In suspension-cultured cells of winter wheat (Triticum aestivum L. cv. Chihokukomugi), the accumulation of soluble secretory proteins in the culture medium was promoted by ABA treatment in comparison with non-treated cells. The total amount of secretory proteins in ABA-treated cells was 1.7-fold higher than that in non-treated cells. The analysis of two-dimensional electrophoresis revealed that at least twelve secretory proteins were induced by ABA, and these were named WAS (wheat ABA-induced secretory) proteins 1 to 12. N-terminal amino acid sequence analysis of WAS proteins revealed the sequences of WAS-2 and WAS-3. Homology searches showed that WAS-2 had 55% identity with the N-terminus of the wheat chemically induced gene (WCI-5 gene) product. WAS-3 was also shown to have 93% identity with the N-terminus of the barley protein R, a typical member of thaumatin-like proteins (TLPs). Immunoblot analysis also suggested that WAS-3 was related to protein R. These results suggest that exogenous ABA induces some basic secretory proteins that are related to the plant defense system in wheat.