Differential induction of sesquiterpene metabolism in tobacco cell suspension cultures by methyl jasmonate and fungal elicitor.
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.
Mandujano-Chávez
A
A
Agronomy Department, University of Kentucky, Lexington 40546-0091, USA.
Schoenbeck
M A
MA
Ralston
L F
LF
Lozoya-Gloria
E
E
Chappell
J
J
D000085:Acetates / Q000494:pharmacology*; D000595:Amino Acid Sequence; D001483:Base Sequence; D019755:Carbon-Carbon Lyases / Q000235:genetics; D002478:Cells, Cultured; D002480:Cellulase / Q000494:pharmacology; D003517:Cyclopentanes / Q000494:pharmacology*; D017931:DNA Primers / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D005656:Fungal Proteins / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D008969:Molecular Sequence Data; D054883:Oxylipins; D010937:Plant Growth Regulators / Q000494:pharmacology; D010947:Plants, Toxic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012717:Sesquiterpenes / Q000378:metabolism*; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D000085:Acetates; D003517:Cyclopentanes; D017931:DNA Primers; D018744:DNA, Plant; D005656:Fungal Proteins; D054883:Oxylipins; D010937:Plant Growth Regulators; D012333:RNA, Messenger; D018749:RNA, Plant; D012717:Sesquiterpenes; C081843:capsidiol; C072239:methyl jasmonate; D002480:Cellulase; D019755:Carbon-Carbon Lyases; C051130:trichodiene synthetase