Induction of Senescence and Identification of Differentially Expressed Genes in Tomato in Response to Monoterpene

Abstract

Monoterpenes, which are among the major components of plant essential oils, are known for their ecological roles as well for pharmaceutical properties. Geraniol, an acyclic monoterpene induces cell cycle arrest and apoptosis/senescence in various cancer cells and plants; however, the genes involved in the process and the underlying molecular mechanisms are not well understood. In this study, we demonstrate that treatment of tomato plants with geraniol results in induction of senescence due to a substantial alteration in transcriptome. We have identified several geraniol-responsive protein encoding genes in tomato using suppression subtractive hybridization (SSH) approach. These genes comprise of various components of signal transduction, cellular metabolism, reactive oxygen species (ROS), ethylene signalling, apoptosis and DNA damage response. Upregulation of NADPH oxidase and antioxidant genes, and increase in ROS level after geraniol treatment point towards the involvement of ROS in geraniol-mediated senescence. The delayed onset of seedling death and induced expression of geraniol-responsive genes in geraniol-treated ethylene receptor mutant (Nr) suggest that geraniol-mediated senescence involves both ethylene dependent and independent pathways. Moreover, expression analysis during tomato ripening revealed that geraniol-responsive genes are also associated with the natural organ senescence process.

Methyl Jasmonate-Elicited Transcriptional Responses and Pentacyclic Triterpene Biosynthesis in Sweet Basil

“…The SSH library was generated according to the PCR-Select cDNA Substraction kit instruction manual (Takara) as previously described (Ghosh et al, 2013). In brief, poly(A+) RNA was isolated from the total RNAs using a mRNA purification kit (Qiagen) and 2 mg of purified poly(A+) RNA was reverse transcribed using avian myeloblastosis virus reverse transcriptase.…”

“…Plants synthesize and accumulate these compounds in specific tissue types perhaps for autotoxicity avoidance, because many of the secondary metabolites are known to be phytotoxic (Reigosa and Malvido-Pazos, 2007;Ghosh et al, 2013). Moreover, the sites of biosynthesis may not necessarily be the sites of storage, and long-distance transport via the xylem, phloem, or apoplast is also possible (Wink, 2010b).…”

Plant Senescence: The Role of Volatile Terpene Compounds (VTCs)

“…Other studies have also reported that geraniol binds and inhibits the activity of 3-hydroxy-3-methylglutaryl-CoA reductase, the enzyme that converts HMG-CoA to mevalonic acid and subsequently reduces the cell growth [64]. These reports suggest that monoterpenes, suggested that geraniol-mediated senescence involves both ethylene dependent and independent pathways [63]. Using detached lima bean leaves (Phaseoluslunatus L), [71] demonstrated that exogenous applications of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid, enhance JA-induced VTC emission.…”

“…Due to limited study in this area it is still unclear if VTCs serve as signal molecules at the initiation of the senescence process or a direct causal effect of senescence. [62] and in most cases, result in plant senescence [63]. Using suppression subtractive hybridization (SSH) approach, several geraniol-responsive proteins encoding genes for signal transduction, cellular metabolism, reactive oxygen species (ROS), ethylene signaling, apoptosis and DNA damage response have been reported in tomato [63].…”

“…[62] and in most cases, result in plant senescence [63]. Using suppression subtractive hybridization (SSH) approach, several geraniol-responsive proteins encoding genes for signal transduction, cellular metabolism, reactive oxygen species (ROS), ethylene signaling, apoptosis and DNA damage response have been reported in tomato [63]. Treatment of plants with geraniol saw early senescence process and upregulation of NADPH oxidase and antioxidant gene and also increased ROS level, suggesting the role of ROS in geraniol-mediated senescence.…”