Figure 1.
Monoterpenes used to study the plant responses.
Geraniol can be metabolized into geranyl acetate, β-citronellol, geranial and neral by the action endogenous plant enzymes. The geometric isomers geranial and neral are known as trans-citral (citral-A) and cis-citral (citral-B), respectively.
Figure 2.
Monoterpene-induced physiological changes in tomato.
(A) Development of necrosis in leaves of 45-days old tomato plants and 15-days old tomato seedlings-treated with monoterpene volatiles geraniol, geranyl acetate, citral and β-citronellol. Photographs were taken at 48 and 72 hr after volatile treatments to tomato seedlings and plants, respectively. Trypan blue staining of the leaves, taken from 48 hr monoterpene volatile-treated plants, was carried out to determine the extent of cell death. (B) The electrolyte leakage rate from the leaves was measured at 12 hr after treatment of tomato plants with monoterpene volatiles. Data are mean ± SEM (n = 3).
Figure 3.
Phytotoxic effect of geraniol on tomato seedlings.
Seedlings were fed with MS medium containing 50 µM to 10 mM geraniol, 20% DMSO and 100 mM ethanol. Seedlings treated with geraniol showed rapid loss of vigor and viability.
Figure 4.
Functional categorization of geraniol-responsive transcripts based on Gene Ontology (GO) biological process (A), cellular component (B) and molecular function (C).
Figure 5.
Expression profiles of geraniol-responsive transcripts.
Tomato seedlings were treated with 10-PCR analysis was carried out for 50 genes selected from SSH library. Data are mean (n = 3). Tomato actin was used as endogenous control.
Figure 6.
H2O2 concentration measured in tomato seedlings after treatment with geraniol.
Seedlings were placed in MS media containing geraniol (50 µM to 10 mM) or 20% DMSO (control). Data are mean ± SEM (n = 3).
Figure 7.
Induced expression of geraniol-responsive genes in ethylene receptor mutant (Nr) seedlings after geraniol treatment.
Transcript level of geraniol-responsive genes at 30 min of treatment with 10 mM geraniol, relative to 0 hr. Data are mean ± SEM (n = 3). G8- NAM-like protein (GH203680), G11- xyloglucan endotransglucosylase-hydrolase (GH205301), G13- C2H2-type zinc finger protein (GH203536), G14- putative scarecrow protein (GH204307), G33- bZIP DNA-binding protein (GH203992), G35- ABA 8′-hydroxylase (GH204050), G44- BAG-domain protein 1/regulator of cell death (GH204276), G46- CCR4 associated factor 1-related protein (GH204364), G47- lipoxygenase (GH204408), G48- transcriptional activator CBF1 (GH204429).
Figure 8.
Up-regulation of geraniol-responsive genes at the onset of fruit senescence.
(A) Tomato fruits used in this study: mature green (MG), breaker (BR), pink (P) and red ripe (RR). (B) Transcript level of 25 geraniol-responsive genes was determined in different ripening stages of fruits by qRT-PCR analysis. Tomato actin was used as endogenous control. Data are mean (n = 3).