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Abstract Detail

Genomics / Proteomics

Tuominen , Lindsey K [1], Du, Lei [2], Payyavula, Raja [3], Wilson, Mark [4], Nyamdari, Batbayar [5], Harding, Scott A [5], Tsai, Chung-Jui [5].

Populus tremuloides cell suspension cultures show distinct transcriptional responses for a phenylpropanoid pathway elicitor and two core pathway enzyme inhibitorsα.

Populus secondary metabolism is characterized by an array of phenylpropanoid compounds that can collectively account for up to 30% of tissue dry mass.  Separate, potentially competing biosynthetic branch pathways are thought to produce diverse subclasses of these compounds.  Here, we grew heterotrophic cell suspension cultures of P. tremuloides in the presence of two different enzyme inhibitors to constrain two early, adjacent steps in the phenylpropanoid core pathway, with or without a defense elicitor known to stimulate phenylpropanoid metabolism (MeJA) in order to study the role of gene expression in phenylpropanoid partitioning and perturbation.  Piperonylic acid (PIP) is capable of enzymatically inhibiting cinnamate-4-hydroxylase (C4H), while α-aminooxy-β-phenylpropionic acid (AOPP) is capable of inhibiting phenylalanine ammonia lyase (PAL).  Cellular metabolic profiles showed changes in core phenylpropanoid metabolites, flavonoid derivatives, amino acids, and citric acid cycle metabolites depending on whether AOPP, PIP, MeJA, or combined inhibitor/elicitor were used.  Microarray and q-RT-PCR analyses were used to assess whether the observed metabolic responses were driven primarily by metabolic-level or transcript-level changes.  Two-way ANOVA was carried out separately on two experimental trials; results indicated that elicitor treatment produced the majority of statistically significant changes in transcription.  Relative expression of PAL and C4H isoforms was elevated under MeJA treatment, consistent with transcriptionally-regulated phenylpropanoid pathway elicitation.  PAL and C4H isoforms were also upregulated under AOPP treatment and had a greater-than-additive response in cells treated with both MeJA and AOPP.  In contrast, PIP treated cells exhibited upregulation only in one C4H isoform regardless of elicitor status, consistent with a response to metabolic conditions.  While monolignol biosynthetic genes were mainly responsive to MeJA treatment, the branch pathways towards and within flavonoid/condensed tannin biosynthesis were responsive to both elicitor and inhibitor treatments.  Such differential responses were also observed for several nitrogen- and citric acid cycle-related genes.  AOPP and MeJA treatments evidenced an upregulaton of pyruvate dehydrogenase and ATP citrate lyase genes, possibly indicating an indirect influence of phenylpropanoid demand on fatty acid metabolism.  Overall, these results provide transcriptional support for previous metabolically-grounded suggestions that (a) phenylpropanoid branch pathways are transcriptionally regulated in part based on status of core pathway metabolites and (b) carbon and nitrogen metabolism exhibit cross-talk via phenylalanine.

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1 - Metropolitan State University, Department of Natural Sciences, 700 East 7th Street, Saint Paul, MN, 55106, USA
2 - Karolinska Institute, Department of Medicine, Stockholm, 17176, Sweden
3 - Oak Ridge National Laboratory, Biosciences Division, Oak Ridge, TN, 37831, USA
4 - Coca Cola Enterprises, Atlanta, GA, 30301, USA
5 - The University of Georgia, Warnell School of Forestry & Natural Resources & Department of Genetics, Athens, GA, 30602, USA

gene expression
carbon-nitrogen metabolism
secondary metabolism
cell culture.

Presentation Type: Oral Paper:Papers for Topics
Session: 35
Location: Pines South/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 8:45 AM
Number: 35004
Abstract ID:123
Candidate for Awards:Margaret Menzel Award

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