ABSTRACT
Changes in actin cytoskeleton dynamics are one of the crucial players in many physiological as well as non-physiological processes in plant cells. Positioning of actin filament arrays is necessary for successful establishment of primary lines of defense toward pathogen attack, depolymerization leads very often to the enhanced susceptibility to the invading pathogen. On the other hand it was also shown that the disruption of actin cytoskeleton leads to the induction of defense response leading to the expression of PATHOGENESIS RELATED proteins (PR). In this study we show that pharmacological actin depolymerization leads to the specific induction of genes in salicylic acid pathway but not that involved in jasmonic acid signaling. Life imaging of leafs of Arabidopsis thaliana with GFP-tagged fimbrin (GFP-fABD2) treated with 1 mM salicylic acid revealed rapid disruption of actin filaments resembling the pattern viewed after treatment with 200 nM latrunculin B. The effect of salicylic acid on actin filament fragmentation was prevented by exogenous addition of phosphatidic acid, which binds to the capping protein and thus promotes actin polymerization. The quantitative evaluation of actin filament dynamics is also presented.
Subject(s)
Actins/metabolism , Arabidopsis/metabolism , Salicylic Acid/metabolism , Signal Transduction , Actin Cytoskeleton/drug effects , Actin Cytoskeleton/metabolism , Arabidopsis/cytology , Arabidopsis/drug effects , Arabidopsis/genetics , Cyclopentanes/metabolism , Cytoplasmic Streaming/drug effects , Gene Expression Regulation, Plant/drug effects , Oxylipins/metabolism , Phosphatidic Acids/pharmacology , Plant Epidermis/cytology , Plant Epidermis/drug effects , Plant Epidermis/metabolism , Salicylic Acid/pharmacology , Signal Transduction/drug effects , Signal Transduction/geneticsABSTRACT
The biosynthetic pathway of monoterpenoid indole alkaloids in Catharanthus roseus is located throughout various membranes at both the cellular and intercellular levels. ATP-binding cassette (ABC) transporters are known to export vincristine and vinblastine from human cancer cells. It has recently been shown that ABC transporters are also involved in the transport of various monoterpenoid alkaloids in Catharanthus roseus cells. Over-expression of an ABC transporter in this plant might therefore affect the regulation of the alkaloid biosynthetic pathway. CjMDR1, an ABC transporter gene originally isolated from Coptis japonica, was expressed in Catharanthus roseus cell cultures. Cells showing a positive PCR signal of the transgene in both cDNA and genomic DNA samples were subject to transport studies using selected substrates. Unexpectedly, transport of the isoquinoline alkaloid berberine, the main substrate of CjMDR1 transporter in Coptis japonica, was not affected as compared with control and wild-type Catharanthus cells. On the other hand, the endogenous alkaloids ajmalicine and tetrahydroalstonine were accumulated significantly more in Catharanthus roseus cells expressing CjMDR1 in comparison with control lines after feeding these alkaloids.
