Dynamic Maize Responses to Aphid Feeding Are Revealed by a Time Series of Transcriptomic and Metabolomic Assays - PubMed (original) (raw)
. 2015 Nov;169(3):1727-43.
doi: 10.1104/pp.15.01039. Epub 2015 Sep 16.
Noe Fernandez-Pozo 1, Annett Richter 1, Eric A Schmelz 1, Matthias Schoettner 1, Martin Schäfer 1, Kevin R Ahern 1, Lisa N Meihls 1, Harleen Kaur 1, Alisa Huffaker 1, Naoki Mori 1, Joerg Degenhardt 1, Lukas A Mueller 1, Georg Jander 2
Affiliations
- PMID: 26378100
- PMCID: PMC4634079
- DOI: 10.1104/pp.15.01039
Dynamic Maize Responses to Aphid Feeding Are Revealed by a Time Series of Transcriptomic and Metabolomic Assays
Vered Tzin et al. Plant Physiol. 2015 Nov.
Abstract
As a response to insect attack, maize (Zea mays) has inducible defenses that involve large changes in gene expression and metabolism. Piercing/sucking insects such as corn leaf aphid (Rhopalosiphum maidis) cause direct damage by acquiring phloem nutrients as well as indirect damage through the transmission of plant viruses. To elucidate the metabolic processes and gene expression changes involved in maize responses to aphid attack, leaves of inbred line B73 were infested with corn leaf aphids for 2 to 96 h. Analysis of infested maize leaves showed two distinct response phases, with the most significant transcriptional and metabolic changes occurring in the first few hours after the initiation of aphid feeding. After 4 d, both gene expression and metabolite profiles of aphid-infested maize reverted to being more similar to those of control plants. Although there was a predominant effect of salicylic acid regulation, gene expression changes also indicated prolonged induction of oxylipins, although not necessarily jasmonic acid, in aphid-infested maize. The role of specific metabolic pathways was confirmed using Dissociator transposon insertions in maize inbred line W22. Mutations in three benzoxazinoid biosynthesis genes, Bx1, Bx2, and Bx6, increased aphid reproduction. In contrast, progeny production was greatly decreased by a transposon insertion in the single W22 homolog of the previously uncharacterized B73 terpene synthases TPS2 and TPS3. Together, these results show that maize leaves shift to implementation of physical and chemical defenses within hours after the initiation of aphid feeding and that the production of specific metabolites can have major effects in maize-aphid interactions.
© 2015 American Society of Plant Biologists. All Rights Reserved.
Figures
Figure 1.
Overview of maize transcriptome and metabolome responses to aphid feeding. A, PLS-DA plots of 1,607 genes identified by transcript profiling (RNA-Seq) of inbred line B73 infested with aphids for the indicated time periods. Ovals indicate 95% confidence intervals. B, PLS-DA of 319 mass signals (negative ion mode) identified by LC-TOF-MS. Ovals indicate 95% confidence intervals. Similar data for the positive ion mode are shown in
Supplemental Figure S3
. C and D, Number of individual transcripts and mass spectrometry features that were significantly up- or down-regulated at each time point, respectively. P < 0.05 (FDR adjusted), and fold change greater than 2 or less than 0.5.
Figure 2.
Overview of gene expression clusters calculated by K-means clustering. A, Pearson correlation was used to identify six clusters involving a total of 1,607 transcripts with significant expression profile changes for at least one time point after the initiation of aphid feeding. The total number of transcripts in each cluster is indicated, and data for individual genes are shown in light gray. Average expression responses for each cluster are shown in red. All genes selected for this analysis have significant differences of 2-fold (up- or down-regulated), P < 0.05 (FDR adjusted). B, Overrepresentation analysis of each cluster using the MetGenMAP Web site to identify metabolic functions that are being regulated.
Figure 3.
Identification of plant hormone signatures based on transcriptomic data. The analysis was conducted using the Hormonometer program (Volodarsky et al., 2009). Red shading indicates a positive correlation between the maize aphid treatment and a particular hormone response; blue shading indicates a negative correlation. MJ, Methyl jasmonate; ACC, 1-aminocyclopropane-1-caroxylic acid (a metabolic precursor of ethylene); ABA, abscisic acid; IAA, indole-3-acetic acid, GA, GA3; BR, brassinosteroid; SA, salicylic acid.
Figure 4.
Effects of aphid feeding on jasmonic acid pathway gene expression and metabolites. A, Schematic diagram of the jasmonic acid biosynthesis pathway. The dashed arrow represents multiple enzymatic steps. Metabolites shaded in blue were measured. B, Transcript and metabolite abundance after aphid infestation. Values are means ±
se
(n = 5). *, P < 0.05 by Student’s t test relative to uninfested controls and fold change greater than 2 or less than 0.5.
Figure 5.
Effects of aphid feeding on genes and metabolites of the aromatic amino acids, salicylic acid, auxin, and other metabolites derived from the shikimate pathway. A, Pathway schematic. Measured metabolites are shaded in blue. B, Gene and metabolite abundance. Values are means ±
se
(n = 5). *, P < 0.05 by Student’s t test relative to uninfested controls, and fold change greater than 2 or less than 0.5.
Figure 6.
Effects of aphid feeding on benzoxazinoid-related genes and metabolites. A, Maize benzoxazinoid biosynthesis pathway. B, Genes and metabolites that were significantly altered by aphid feeding for at least one time point. Values are means ±
se
(n = 5). *, P < 0.05 by Student’s t test relative to uninfested controls and fold change greater than 2 or less than 0.5. C, DIMBOA-Glc levels in wild-type W22 and bx1::Ds, bx2::Ds, and bx6::Ds transposon knockout mutants. Values are means ±
se
(n = 6–11). *, P < 0.05 by Student’s t test relative to the wild type. FW, Fresh weight; ND, not detected. D, Corn leaf aphid progeny production on the same lines as in C. Values are means ±
se
(n = 6–11). *, P < 0.05 by Student’s t test relative to the wild type. DIM2BOA-Glc, 2,4-Dihydroxy-7,8-dimethoxy-1,4-benzoxazin-3-one glucoside; HMBOA-Glc, 2-hydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside.
Figure 7.
Effect of aphid feeding on terpene biosynthesis. A, B73 TPS2 and TPS3 gene expression in response to aphid feeding on B73. Values are means ±
se
(n = 5). *, P < 0.05 by Student’s t test. B, TPS2/3 gene expression in wild-type W22 with and without aphids (n = 7). C, _TPS2/3 g_ene expression in wild-type W22 and tps2/3::Ds from a segregating population (n = 7–10). D, Aphid reproduction on wild-type W22 and tps2/3::Ds from a segregating population. *, P < 0.05 by Student’s t test (n = 7–10). E, Terpene abundance in wild-type W22 and tps2/3::Ds with and without aphid feeding. *, P < 0.05 by Student’s t test (n = 3–7).
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