Induction by methyl jasmonate of embryogenesis-related proteins and mRNAs in Nicotinia plumbaginifolia

Abstract

Upon treatment with jasmonic acid methyl ester (methyl jasmonate, JaMe) detached leaf segments of in vitro-regenerated plants of Nicotiana plumbaginifolia accumulate novel abundant proteins and mRNAs. Among them are late embryogenesis abundant ( Lea) transcripts, which appear in a temporally defined manner during somatic embryogenesis and normally do not occur in mature plant organs such as leaves or roots. To pursue this observation, the induction by methyl jasmonate of embryogenesis-related proteins and mRNAs in leaf and root tissues was investigated by comparing the two-dimensional patterns of in vivo- and in vitro-translated polypeptides. We found a selective reinduction by methyl jasmonate of several embryo-specific proteins and mRNAs, whose expression is associated with the formation of early and mature globular stages. Some of the jasmonate-induced embryo-specific proteins were also expressed in leaves, but not in roots, in response to abscisic acid (ABA) or osmotic stress (sorbitol) treatment, suggesting their role in osmoprotection of leaf and embryo tissues as discussed for LEA proteins. Western blot analyses with polyclonal antibodies raised against jasmonate-induced proteins (JIPs) of Mr 23 000 from barley highlighted the tissue-specific reappearance of a group of closely related, evolutionarily conserved embryo-specific proteins in N. plumbaginifolia leaves after JaMe, ABA and sorbitol treatment. Actin and tubulin, for which the transcript contents were estimated, increased in amount in the course of somatic embryogenesis, but did not change in abundance under the various conditions of treatment. Our results imply a specific role of JaMe in controlling gene expression during somatic embryogenesis in N. plumbaginifolia.