cellulase and methyl-jasmonate

When growth-phase cell suspension cultures of Capsicum annuum were treated with cellulase-elicitor preparation at 3 microg/ml, the level of capsidiol was transiently increased in the culture media rather than in the cells reaching its maximum approx 24 h after treatment. With methyl jasmonate it took 18 h. Elicitor treatment doubled phospholiphase A(2) (PLA(2)) activity but simultaneous treatment with aristolochic acid, a PLA(2) inhibitor, inhibited sesquiterpenoid accumulation as well as PLA(2) activity. Mastoparan, a G protein activator, treatment also increased PLA(2) activity and capsidiol production. Taken together, the present study shows that induction of capsidiol production in the C. annuum is mediated by PLA(2) activation.

Topics: Acetates; Aristolochic Acids; Capsicum; Cells, Cultured; Cellulase; Chromatography, Gas; Cyclopentanes; Intercellular Signaling Peptides and Proteins; Oxylipins; Peptides; Phospholipase A2 Inhibitors; Phospholipases A2; Sesquiterpenes; Time Factors; Wasp Venoms

Jasmonates are well documented for their ability to modulate the expression of plant genes and to influence specific aspects of disease/pest resistance traits. We and others have been studying the synthesis of sesquiterpene phytoalexins in elicitor/pathogen-challenged plants and have sought to determine if methyl jasmonate (MeJA) could substitute for fungal elicitors in the induction of capsidiol accumulation by tobacco cell cultures. The current results demonstrate that MeJA does in fact induce phytoalexin accumulation, but with a much more delayed induction time course than elicitor. While elicitor treatment induced strong but transient changes in key enzymes of sesquiterpene biosynthesis, sesquiterpene cyclase, and aristolochene/deoxy-capsidiol hydroxylase, MeJA did not. Instead, MeJA caused a protracted induction of cyclase activity and only a low level of hydroxylase activity. MeJA induced the expression of at least two sesquiterpene cyclase genes, including one that had not been observed previously in elicitor-induced mRNA populations. Only a small portion of the total sesquiterpene cyclase mRNA induced by MeJA was associated with polysomal RNA, suggesting that the MeJA treatment imposed both transcriptional and posttranscriptional regulation in tobacco cells. These results are not consistent with MeJA playing a role in orchestrating defense responses in elicitor-treated tobacco cells, but do provide evidence that MeJA induces a subset of genes coding for the biosynthesis of sesquiterpene phytoalexins.

Topics: Acetates; Amino Acid Sequence; Base Sequence; Carbon-Carbon Lyases; Cells, Cultured; Cellulase; Cyclopentanes; DNA Primers; DNA, Plant; Fungal Proteins; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Genes, Plant; Molecular Sequence Data; Nicotiana; Oxylipins; Plant Growth Regulators; Plants, Toxic; RNA, Messenger; RNA, Plant; Sequence Homology, Amino Acid; Sequence Homology, Nucleic Acid; Sesquiterpenes