Limits...
Terpene synthases and their contribution to herbivore-induced volatile emission in western balsam poplar (Populus trichocarpa).

Irmisch S, Jiang Y, Chen F, Gershenzon J, Köllner TG - BMC Plant Biol. (2014)

Bottom Line: Gypsy moth-feeding on individual leaves of P. trichocarpa trees resulted in induced volatile emission from damaged leaves, but not from undamaged adjacent leaves.Our data indicate that the formation of herbivore-induced volatile terpenes in P. trichocarpa is mainly regulated by transcript accumulation of multiple TPS genes and is likely mediated by jasmonates.The specific local emission of volatiles from herbivore-damaged leaves might help herbivore enemies to find their hosts or prey in the tree canopy.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, Jena, Germany. koellner@ice.mpg.de.

ABSTRACT

Background: As a response to caterpillar feeding, poplar releases a complex mixture of volatiles which comprises several classes of compounds. Poplar volatiles have been reported to function as signals in plant-insect interactions and intra- and inter-plant communication. Although the volatile blend is dominated by mono- and sesquiterpenes, there is much to be learned about their formation in poplar.

Results: Here we report the terpene synthase (TPS) gene family of western balsam poplar (Populus trichocarpa) consisting of 38 members. Eleven TPS genes (PtTPS5-15) could be isolated from gypsy moth (Lymantria dispar)-damaged P. trichocarpa leaves and heterologous expression in Escherichia coli revealed TPS activity for ten of the encoded enzymes. Analysis of TPS transcript abundance in herbivore-damaged leaves and undamaged control leaves showed that seven of the genes, PtTPS6, PtTPS7, PtTPS9, PtTPS10, PtTPS12, PtTPS13 and PtTPS15, were significantly upregulated after herbivory. Gypsy moth-feeding on individual leaves of P. trichocarpa trees resulted in induced volatile emission from damaged leaves, but not from undamaged adjacent leaves. Moreover, the concentration of jasmonic acid and its isoleucine conjugates as well as PtTPS6 gene expression were exclusively increased in the damaged leaves, suggesting that no systemic induction occurred within the tree.

Conclusions: Our data indicate that the formation of herbivore-induced volatile terpenes in P. trichocarpa is mainly regulated by transcript accumulation of multiple TPS genes and is likely mediated by jasmonates. The specific local emission of volatiles from herbivore-damaged leaves might help herbivore enemies to find their hosts or prey in the tree canopy.

Show MeSH

Related in: MedlinePlus

Transcript abundance of terpene synthase genes in herbivore-damaged(herb)and undamaged control(ctr)leaves ofP. trichocarpa. Caterpillars were allowed to feed for 24 h on apical LPI3 (leaf plastochron index 3) leaves. Gene expression was determined by qRT-PCR. Means and standard errors are shown (n = 5). The student’s t-test was used to test for statistical significance. Asterisks indicate a significant difference between herbivore-infested and untreated control leaves. ctr, control treatment; herb, herbivory.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4197230&req=5

Fig3: Transcript abundance of terpene synthase genes in herbivore-damaged(herb)and undamaged control(ctr)leaves ofP. trichocarpa. Caterpillars were allowed to feed for 24 h on apical LPI3 (leaf plastochron index 3) leaves. Gene expression was determined by qRT-PCR. Means and standard errors are shown (n = 5). The student’s t-test was used to test for statistical significance. Asterisks indicate a significant difference between herbivore-infested and untreated control leaves. ctr, control treatment; herb, herbivory.

Mentions: To analyze whether the expression of PtTPS5-15 is influenced by herbivory, the transcript abundance of these genes was measured using qRT-PCR in apical, herbivore-damaged leaves (LPI3, for a detailed description of leaf plastochron index (LPI) see material and methods) compared to the respective undamaged leaves from control trees. The expression levels of PtTPS5-15 generally increased after herbivore attack (Figure 3). Six of these genes were slightly upregulated, about 2- to 8-fold, with the increases in transcript accumulation significant for PtTPS9, PtTPS10, PtTPS12 and PtTPS15 but not for PtTPS5 and PtTPS11/14 (Figure 3, Additional file 2: Table S2). Repeated sequencing of amplicons from PtTPS11/14-qRT-PCR reactions revealed a 1:4 ratio of PtTPS11 to PtTPS14 transcript. A larger significant induction could be shown for PtTPS7 and PtTPS13, with 24.1-fold and 13.3-fold higher transcript abundance, respectively, in the damaged leaf compared to the undamaged control leaf (Figure 3). PtTPS6 showed the strongest response to herbivore damage with a 44.1-fold increase in transcript abundance (Figure 3, Additional file 2: Table S2). No qRT-PCR analysis was performed for PtTPS8 as no activity could be observed for the corresponding protein. Altogether the qRT-analysis showed distinct differences in the ΔCq values (CqTPS – Cqhouse-keeping gene) for the identified PtTPS genes (Additional file 2: Table S3). PtTPS11/14 and PtTPS12 had ΔCq-values higher than 15 indicating low expression levels. In contrast, small ΔCq-values were observed for PtTPS6 and PtTPS9 indicating higher transcript abundance compared to the other PtTPS genes.Figure 3


Terpene synthases and their contribution to herbivore-induced volatile emission in western balsam poplar (Populus trichocarpa).

Irmisch S, Jiang Y, Chen F, Gershenzon J, Köllner TG - BMC Plant Biol. (2014)

Transcript abundance of terpene synthase genes in herbivore-damaged(herb)and undamaged control(ctr)leaves ofP. trichocarpa. Caterpillars were allowed to feed for 24 h on apical LPI3 (leaf plastochron index 3) leaves. Gene expression was determined by qRT-PCR. Means and standard errors are shown (n = 5). The student’s t-test was used to test for statistical significance. Asterisks indicate a significant difference between herbivore-infested and untreated control leaves. ctr, control treatment; herb, herbivory.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4197230&req=5

Fig3: Transcript abundance of terpene synthase genes in herbivore-damaged(herb)and undamaged control(ctr)leaves ofP. trichocarpa. Caterpillars were allowed to feed for 24 h on apical LPI3 (leaf plastochron index 3) leaves. Gene expression was determined by qRT-PCR. Means and standard errors are shown (n = 5). The student’s t-test was used to test for statistical significance. Asterisks indicate a significant difference between herbivore-infested and untreated control leaves. ctr, control treatment; herb, herbivory.
Mentions: To analyze whether the expression of PtTPS5-15 is influenced by herbivory, the transcript abundance of these genes was measured using qRT-PCR in apical, herbivore-damaged leaves (LPI3, for a detailed description of leaf plastochron index (LPI) see material and methods) compared to the respective undamaged leaves from control trees. The expression levels of PtTPS5-15 generally increased after herbivore attack (Figure 3). Six of these genes were slightly upregulated, about 2- to 8-fold, with the increases in transcript accumulation significant for PtTPS9, PtTPS10, PtTPS12 and PtTPS15 but not for PtTPS5 and PtTPS11/14 (Figure 3, Additional file 2: Table S2). Repeated sequencing of amplicons from PtTPS11/14-qRT-PCR reactions revealed a 1:4 ratio of PtTPS11 to PtTPS14 transcript. A larger significant induction could be shown for PtTPS7 and PtTPS13, with 24.1-fold and 13.3-fold higher transcript abundance, respectively, in the damaged leaf compared to the undamaged control leaf (Figure 3). PtTPS6 showed the strongest response to herbivore damage with a 44.1-fold increase in transcript abundance (Figure 3, Additional file 2: Table S2). No qRT-PCR analysis was performed for PtTPS8 as no activity could be observed for the corresponding protein. Altogether the qRT-analysis showed distinct differences in the ΔCq values (CqTPS – Cqhouse-keeping gene) for the identified PtTPS genes (Additional file 2: Table S3). PtTPS11/14 and PtTPS12 had ΔCq-values higher than 15 indicating low expression levels. In contrast, small ΔCq-values were observed for PtTPS6 and PtTPS9 indicating higher transcript abundance compared to the other PtTPS genes.Figure 3

Bottom Line: Gypsy moth-feeding on individual leaves of P. trichocarpa trees resulted in induced volatile emission from damaged leaves, but not from undamaged adjacent leaves.Our data indicate that the formation of herbivore-induced volatile terpenes in P. trichocarpa is mainly regulated by transcript accumulation of multiple TPS genes and is likely mediated by jasmonates.The specific local emission of volatiles from herbivore-damaged leaves might help herbivore enemies to find their hosts or prey in the tree canopy.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, Jena, Germany. koellner@ice.mpg.de.

ABSTRACT

Background: As a response to caterpillar feeding, poplar releases a complex mixture of volatiles which comprises several classes of compounds. Poplar volatiles have been reported to function as signals in plant-insect interactions and intra- and inter-plant communication. Although the volatile blend is dominated by mono- and sesquiterpenes, there is much to be learned about their formation in poplar.

Results: Here we report the terpene synthase (TPS) gene family of western balsam poplar (Populus trichocarpa) consisting of 38 members. Eleven TPS genes (PtTPS5-15) could be isolated from gypsy moth (Lymantria dispar)-damaged P. trichocarpa leaves and heterologous expression in Escherichia coli revealed TPS activity for ten of the encoded enzymes. Analysis of TPS transcript abundance in herbivore-damaged leaves and undamaged control leaves showed that seven of the genes, PtTPS6, PtTPS7, PtTPS9, PtTPS10, PtTPS12, PtTPS13 and PtTPS15, were significantly upregulated after herbivory. Gypsy moth-feeding on individual leaves of P. trichocarpa trees resulted in induced volatile emission from damaged leaves, but not from undamaged adjacent leaves. Moreover, the concentration of jasmonic acid and its isoleucine conjugates as well as PtTPS6 gene expression were exclusively increased in the damaged leaves, suggesting that no systemic induction occurred within the tree.

Conclusions: Our data indicate that the formation of herbivore-induced volatile terpenes in P. trichocarpa is mainly regulated by transcript accumulation of multiple TPS genes and is likely mediated by jasmonates. The specific local emission of volatiles from herbivore-damaged leaves might help herbivore enemies to find their hosts or prey in the tree canopy.

Show MeSH
Related in: MedlinePlus