Abstract Detail

Biochemistry, metabolism, carbon flux

Constabel, Peter [1], Ma, David [2], Yoshida, Kazuko [2].

The Gene Regulatory Network of Condensed Tannin Synthesis in Populus.

Condensed tannins are abundant and widespread phenolic phytochemicals in plants, and especially abundant in woody plants. In poplar leaves, the condensed tannins can be a major sink of carbon, with concentrations reaching 25% leaf dry weight. These polymeric phytochemicals are terminal products of the flavonoid pathway, and have been associated with a variety of stress-related ecological functions, including defense against herbivores and pathogens, and nutrient cycling in soils. In poplar, condensed tannin accumulation can be induced by diverse environmental stressors, for example wounding, pathogen attack, and nitrogen deficiency. In order to study this response at the molecular level, we have identified a set of R2R3 MYB transcription factors that regulate condensed tannins accumulation. The poplar MYB134 and MYB115 genes positively regulate the condensed tannins in poplar, and their overexpression in transgenic poplar trees causes a dramatically enhanced accumulation of condensed tannins throughout the plant. The characterization of MYB134 led to the identification of MYB repressors, which we are investigating further. Our results confirm that these new MYBs are functional and act on the flavonoid and condensed tannins pathway. Promoter activation assays using promoter-luciferase constructs in transiently transformed poplar cells indicate that flavonoid genes are direct targets of the activator MYBs, and that this activation can be inhibited by the new MYB repressors. To dissect the action of these repressor-like MYBs, transgenic plants that overexpress the corresponding genes have also been generated. Several repressor MYB-overexpressor plants show a low condensed tannins phenotype, confirming that these MYBs are negative flavonoid and condensed tannin regulators. Transcriptomic analysis using RNAseq will help to delineate specific target genes and pathways for the repressor and activator MYBs. The action of the repressors and activators is being studied using yeast two-hybrid system, in order to test for protein-protein interactions.

1 - University of Victoria, Biology Department and Centre for Forest Biology, Bos 3020 Stn CSC, Victoria, BC, v8n3n5, CA
2 - University of Victoria, Biology Department and Centre for Forest Biology, Box 3020 Stn CSC, Victoria, BC, v8n3n5, CA

Keywords:
phytochemistry
Proanthocyanidin
gene expression
transcription factor
Populus.

Presentation Type: Oral Paper:Papers for Topics
Session: 43
Location: Hall A/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 11:45 AM
Number: 43007
Abstract ID:1244
Candidate for Awards:None