Three major somatic embryogenesis related proteins in Cichorium identified as PR proteins

Abstract

In Cichorium hybrid clone ‘474’ ( C . intybus L., var. sativum× C . endivia L., var. latifolia), the direct somatic embryogenesis process in leaf tissues is accompanied by an overall increase in the amount of proteins secreted into the culture medium. Amongst these, three major protein bands of 38 kDa, 32 kDa and 25 kDa were found in the conditioned media. These extracellular protein bands accumulated in the medium of the embryogenic Cichorium hybrid up to 8‐fold compared with those in the medium of a non‐embryogenic variety. 32 and 25 kDa proteins were purified from the medium and their identities were determined as already described for 38 kDa β‐1,3‐ glucanases. To investigate their possible function in somatic embryogenesis, peptide sequences, serological relationships or biochemical properties revealed that there were at least two acidic chitinases of 32 kDa and one glycosylated osmotin‐like protein of 25 kDa in the embryogenic culture medium. Comparing the amounts of the 38 kDa glucanases, the 32 kDa chitinases, and the 25 kDa osmotin‐like protein present in the conditioned media of the embryogenic ‘474’ hybrid and of a non‐embryogenic variety, a 2–8‐fold higher accumulation of these proteins was observed in the embryogenic hybrid culture medium. This may suggest that part of the accumulation of these three pathogenesis‐related (PR) proteins could be correlated with the somatic embryogenesis process. Their possible involvement in this developmental process is discussed.