Jasmonic Acid Is a Key Regulator of Spider Mite-Induced Volatile Terpenoid and Methyl Salicylate Emission in Tomato  

Abstract

The tomato (Lycopersicon esculentum) mutant def-1, which is deficient in induced jasmonic acid (JA) accumulation upon wounding or herbivory, was used to study the role of JA in the direct and indirect defense responses to phytophagous mites (Tetranychus urticae). In contrast to earlier reports, spider mites laid as many eggs and caused as much damage on def-1 as on wild-type plants, even though def-1 lacked induction of proteinase inhibitor activity. However, the hatching-rate of eggs on def-1 was significantly higher, suggesting that JA-dependent direct defenses enhanced egg mortality or increased the time needed for embryonic development. As to gene expression, def-1 had lower levels of JA-related transcripts but higher levels of salicylic acid (SA) related transcripts after 1 d of spider mite infestation. Furthermore, the indirect defense response was absent in def-1, since the five typical spider mite-induced tomato-volatiles (methyl salicylate [MeSA], 4,8,12-trimethyltrideca-1,3,7,11-tetraene [TMTT], linalool, trans-nerolidol, and trans-b-ocimene) were not induced and the predatory mite Phytoseiulus persimilis did not discriminate between infested and uninfested def-1 tomatoes as it did with wild-type tomatoes. Similarly, the expression of the MeSA biosynthetic gene salicylic acid methyltransferase (SAMT) was induced by spider mites in wild type but not in def-1. Exogenous application of JA to def-1 induced the accumulation of SAMT and putative geranylgeranyl diphosphate synthase transcripts and restored MeSA-and TMTT-emission upon herbivory. JA is therefore necessary to induce the enzymatic conversion of SA into MeSA. We conclude that JA is essential for establishing the spider mite-induced indirect defense response in tomato.

Biosynthesis and emission of insect-induced methyl salicylate and methyl benzoate from rice

“…When applied with exogenous JA, lima bean plants release elevated levels of MeSA similar to those induced by herbivores [9]. When tomato mutant plants deficient in the accumulation of JA were infested with spider mites, emission of MeSA was significantly reduced compared to wild-type plants [1]. These data support that the JA pathway plays an important regulatory role in MeSA production and emission.…”

“…Methyl salicylate (MeSA) is a frequent constituent of insect-induced plant volatiles. It has been detected in the headspace of many insect-infested plants, such as lima bean [2], Arabidopsis [5], tomato [1], and soybean [47]. When tested in its pure, synthetic form, MeSA can attract several types of carnivores [8,10,47], suggesting that MeSA, singly or in combination with other volatiles, is an active signal for indirect defense of tested plants.…”

Induction of a leaf specific geranylgeranyl pyrophosphate synthase and emission of (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene in tomato are dependent on both jasmonic acid and salicylic acid signaling pathways

“…The Tenax tubes were eluted with 2 ml pentane:diethylether (4:1, v/v) with 1.8 g of benzyl acetate as internal standard. One microliter was analyzed using gas chromatograph mass-spectrometry as described by Ament et al (2004). Compounds were identiWed and quantiWed on the basis of the internal standard and synthetic external standards of known concentrations.…”

“…Total RNA was isolated with a Phenol-LiCl based method as described by Verdonk et al (2003). RT-PCR determination of transcript levels was done as described by Ament et al (2004). For each cDNA we determined the number of cycles for which the PCR ampliWcation was not saturated.…”

“…PCR products were visualized by staining with ethidium bromide after separation on agarose gels. QuantiWcation of transcript levels of LeGGPS1 and RUB1 conjugating enzyme (RCE1) was performed as described by Ament et al (2004). PCR ampliWcation of RCE1 fragments (0.723 kb) comprised 20 cycles with forward primer, 5Ј-GATTCTCTCTCAT CAATCAATTCG-3Ј and reverse primer, 5Ј-GCATC CAAACTTTACAGACTCTC-3Ј; of PRP6 fragments (0.427 kb) 23 cycles with forward primer 5Ј-TCAGTC CGACTAGGTTGTGG-3Ј and reverse primer 5Ј-TA GATAAGTGCTTGATGTGCC-3Ј of WIPI-2 fragments (0.601 kb) 14 cycles with forward primer, 5Ј-GA CAAGGTACTAGTAATCAAT-3Ј and reverse primer, 5Ј-CACATAACACACAACTTTGATGCC-3Ј; of LeGGPS2 fragments (0.378 kb) 25 cycles with forward primer 5Ј-CTTTGGATGAGGCTATAATGG-3Ј and reverse primer 5Ј-ATTCGGCGACAGCAACGAG G-3Ј; and of LeGGPS1 fragments (0.327 kb) 27 cycles with forward primer 5Ј-GCAATCAAGGTAAACA AAGCAC-3Ј and reverse primer 5Ј-CAAAGATAA AAGTGCATCCCCTG-3Ј.…”