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1.
Front Plant Sci ; 8: 1342, 2017.
Article in English | MEDLINE | ID: mdl-28824678

ABSTRACT

E-2-hexenal is a volatile compound that is commonly emitted by wounded or stressed plants. It belongs to the group of so-called green leaf volatiles (GLVs), which play an important role in transferring information to plants and insects. While most biosynthetic enzymes upstream of E-2-hexenal have been studied extensively, much less is known about the enzyme responsible for the conversion from Z-3- to E-2-hexenal. In this study we have identified two (3Z):(2E)-hexenal isomerases (HIs) from cucumber fruits by classical biochemical fractionation techniques and we were able to confirm their activity by heterologous expression. Recombinant protein of the HIs did not only convert the leaf aldehyde Z-3-hexenal to E-2-hexenal, but also (Z,Z)-3,6-nonadienal to (E,Z)-2,6-nonadienal, these last two representing major flavor volatiles of cucumber fruits. Transient expression of the cucumber HIs in Nicotiana benthamiana leaves drastically changed the GLV bouquet of damaged plants from a Z-3- to an E-2-enriched GLV profile. Furthermore, transcriptional analysis revealed that the two HIs showed distinct expression patterns. While HI-1 was specifically expressed in the flesh of cucumber fruits HI-2 was expressed in leaves as well. Interestingly, wounding of cucumber leaves caused only a slight increase in HI-2 transcript levels. These results demonstrate that cucumber HIs are responsible for the rearrangement of Z-3-aldehydes in both leaves and fruits. Future research will reveal the physiological importance of an increased conversion to E-2-aldehydes for plants and insects.

2.
Plant J ; 83(6): 1082-96, 2015 Sep.
Article in English | MEDLINE | ID: mdl-26243404

ABSTRACT

Plants are known to be responsive to volatiles, but knowledge about the molecular players involved in transducing their perception remains scarce. We study the response of Arabidopsis thaliana to E-2-hexenal, one of the green leaf volatiles (GLV) that is produced upon wounding, herbivory or infection with pathogens. We have taken a transcriptomics approach to identify genes that are induced by E-2-hexenal, but not by defence hormones or other GLVs. Furthermore, by studying the promoters of early E-2-hexenal-induced genes we determined that the only statistically enriched cis-element was the W-box motif. Since members of the plant-specific family of WRKY transcription factors act in trans on this cis-element, we focused on WRKY6, 40 and 53 that were most strongly induced by E-2-hexenal. Root elongation of Arabidopsis seedlings of the wrky40 wrky6 double mutant was much less inhibited than in wt plants, similar to the E-2-hexenal-responsive mutant her1, which is perturbed in γ-amino butyric acid (GABA) metabolism. The induction of several of the E-2-hexenal-specific genes was much higher in the wrky40, wrky6 or wrky40 wrky6 mutants, including GAD4, a glutamate decarboxylase that catalyzes the formation of GABA from glutamate. In conclusion, WRKY6 and 40 seem to act as important players transducing E-2-hexenal perception.


Subject(s)
Aldehydes/metabolism , Arabidopsis Proteins/metabolism , Arabidopsis/metabolism , Plant Leaves/metabolism , Transcription Factors/metabolism , Aldehydes/pharmacology , Arabidopsis/drug effects , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Gene Expression Profiling , Gene Expression Regulation, Plant/drug effects , Mutation , Plant Leaves/genetics , Plant Roots/genetics , Plant Roots/growth & development , Plant Roots/metabolism , Regulatory Sequences, Nucleic Acid , Transcription Factors/genetics , gamma-Aminobutyric Acid/metabolism
3.
BMC Genomics ; 15: 402, 2014 May 27.
Article in English | MEDLINE | ID: mdl-24884371

ABSTRACT

BACKGROUND: Glandular trichomes are production and storage organs of specialized metabolites such as terpenes, which play a role in the plant's defense system. The present study aimed to shed light on the regulation of terpene biosynthesis in Solanum lycopersicum trichomes by identification of transcription factors (TFs) that control the expression of terpene synthases. RESULTS: A trichome transcriptome database was created with a total of 27,195 contigs that contained 743 annotated TFs. Furthermore a quantitative expression database was obtained of jasmonic acid-treated trichomes. Sixteen candidate TFs were selected for further analysis. One TF of the MYC bHLH class and one of the WRKY class were able to transiently transactivate S. lycopersicum terpene synthase promoters in Nicotiana benthamiana leaves. Strikingly, SlMYC1 was shown to act synergistically with a previously identified zinc finger-like TF, Expression of Terpenoids 1 (SlEOT1) in transactivating the SlTPS5 promoter. CONCLUSIONS: High-throughput sequencing of tomato stem trichomes led to the discovery of two transcription factors that activated several terpene synthase promoters. Our results identified new elements of the transcriptional regulation of tomato terpene biosynthesis in trichomes, a largely unexplored field.


Subject(s)
Alkyl and Aryl Transferases/genetics , Plant Proteins/genetics , Solanum lycopersicum/genetics , Transcription Factors/genetics , Contig Mapping , Cyclopentanes/pharmacology , Databases, Genetic , High-Throughput Nucleotide Sequencing , Solanum lycopersicum/drug effects , Solanum lycopersicum/metabolism , Oxylipins/pharmacology , Plant Leaves/genetics , Plant Leaves/metabolism , Plant Proteins/metabolism , Promoter Regions, Genetic , Sequence Analysis, RNA , Terpenes/chemistry , Terpenes/metabolism , Transcription Factors/metabolism , Transcriptional Activation/drug effects , Transcriptome/drug effects
4.
Plant Mol Biol ; 84(3): 345-57, 2014 Feb.
Article in English | MEDLINE | ID: mdl-24142382

ABSTRACT

Terpene biosynthesis in tomato glandular trichomes has been well studied, with most if not all terpene synthases (TPSs) being identified. However, transcription factors (TFs) that regulate TPSs have not yet been discovered from tomato. In order to unravel the transcriptional regulation of the Solanum lycopersicum linalool synthase (SlMTS1, recently renamed SlTPS5) gene in glandular trichomes, we functionally dissected its promoter. A 207 bp fragment containing the minimal promoter and the 5'UTR appeared to be sufficient for trichome-specific expression in transgenic plants. Yeast-one-hybrid screens with this fragment identified a glandular trichome-specific transcription factor, designated Expression of Terpenoids 1 (SlEOT1). SlEOT1 is a member of a conserved family of TFs that includes the Arabidopsis Stylish 1 (AtSTY1) and Short Internode (AtSHI) genes. The EOT1 protein localized to the nucleus and specifically transactivated the SlTPS5 promoter in Nicotiana benthamiana leaves.


Subject(s)
Alkyl and Aryl Transferases/genetics , Promoter Regions, Genetic , Solanum lycopersicum/metabolism , Terpenes/metabolism , Alkyl and Aryl Transferases/chemistry , Amino Acid Sequence , Cell Nucleus/enzymology , Molecular Sequence Data , Plants, Genetically Modified , Real-Time Polymerase Chain Reaction , Sequence Homology, Amino Acid , Zinc Fingers
5.
Plant Physiol ; 157(2): 770-89, 2011 Oct.
Article in English | MEDLINE | ID: mdl-21813655

ABSTRACT

Compounds of the terpenoid class play numerous roles in the interactions of plants with their environment, such as attracting pollinators and defending the plant against pests. We show here that the genome of cultivated tomato (Solanum lycopersicum) contains 44 terpene synthase (TPS) genes, including 29 that are functional or potentially functional. Of these 29 TPS genes, 26 were expressed in at least some organs or tissues of the plant. The enzymatic functions of eight of the TPS proteins were previously reported, and here we report the specific in vitro catalytic activity of 10 additional tomato terpene synthases. Many of the tomato TPS genes are found in clusters, notably on chromosomes 1, 2, 6, 8, and 10. All TPS family clades previously identified in angiosperms are also present in tomato. The largest clade of functional TPS genes found in tomato, with 12 members, is the TPS-a clade, and it appears to encode only sesquiterpene synthases, one of which is localized to the mitochondria, while the rest are likely cytosolic. A few additional sesquiterpene synthases are encoded by TPS-b clade genes. Some of the tomato sesquiterpene synthases use z,z-farnesyl diphosphate in vitro as well, or more efficiently than, the e,e-farnesyl diphosphate substrate. Genes encoding monoterpene synthases are also prevalent, and they fall into three clades: TPS-b, TPS-g, and TPS-e/f. With the exception of two enzymes involved in the synthesis of ent-kaurene, the precursor of gibberellins, no other tomato TPS genes could be demonstrated to encode diterpene synthases so far.


Subject(s)
Alkyl and Aryl Transferases/genetics , Plant Proteins/genetics , Solanum lycopersicum/genetics , Alkyl and Aryl Transferases/metabolism , Cyclopentanes/pharmacology , Cytosol/enzymology , Diterpenes, Kaurane/metabolism , Evolution, Molecular , Gene Expression Regulation, Enzymologic , Gene Expression Regulation, Plant , Genome, Plant , Solanum lycopersicum/drug effects , Solanum lycopersicum/enzymology , Mitochondria/enzymology , Molecular Sequence Data , Monoterpenes/metabolism , Multigene Family , Oxylipins/pharmacology , Plant Proteins/metabolism
6.
Plant Mol Biol ; 77(4-5): 323-36, 2011 Nov.
Article in English | MEDLINE | ID: mdl-21818683

ABSTRACT

Solanum lycopersicum and Solanum habrochaites (f. typicum) accession PI127826 emit a variety of sesquiterpenes. To identify terpene synthases involved in the production of these volatile sesquiterpenes, we used massive parallel pyrosequencing (RNA-seq) to obtain the transcriptome of the stem trichomes from these plants. This approach resulted initially in the discovery of six sesquiterpene synthase cDNAs from S. lycopersicum and five from S. habrochaites. Searches of other databases and the S. lycopersicum genome resulted in the discovery of two additional sesquiterpene synthases expressed in trichomes. The sesquiterpene synthases from S. lycopersicum and S. habrochaites have high levels of protein identity. Several of them appeared to encode for non-functional proteins. Functional recombinant proteins produced germacrenes, ß-caryophyllene/α-humulene, viridiflorene and valencene from (E,E)-farnesyl diphosphate. However, the activities of these enzymes do not completely explain the differences in sesquiterpene production between the two tomato plants. RT-qPCR confirmed high levels of expression of most of the S. lycopersicum sesquiterpene synthases in stem trichomes. In addition, one sesquiterpene synthase was induced by jasmonic acid, while another appeared to be slightly repressed by the treatment. Our data provide a foundation to study the evolution of terpene synthases in cultivated and wild tomato.


Subject(s)
Alkyl and Aryl Transferases/chemistry , Plant Proteins/chemistry , RNA, Plant/chemistry , Solanum lycopersicum/genetics , Solanum/genetics , Alkyl and Aryl Transferases/genetics , DNA, Complementary/chemistry , Gene Library , Solanum lycopersicum/enzymology , Plant Proteins/genetics , Recombinant Fusion Proteins/metabolism , Sequence Analysis, RNA , Sesquiterpenes/metabolism , Solanum/enzymology
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