The Impact of Genomics on Advances in Herbivore Defense and Secondary Metabolism in Populus

Constabel, C. Peter; Lindroth, Richard L.

doi:10.1007/978-1-4419-1541-2_13

Cited by 24 publications

(20 citation statements)

References 103 publications

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“…This was perhaps due to a difference between the relative expression of the PA pathway in leaves and roots. Whereas leaves accumulate PAs together with large amounts of other phenolics, including salicinoids, flavonols, and hydroxycinnamic acid esters (Constabel and Lindroth, 2010), poplar roots have a much simpler phenolic profile that is dominated by the PAs (C.P. Constabel, unpublished data).…”

Section: Myb182 Is a Repressor That Reduces Pa And Anthocyanin Accumumentioning

confidence: 99%

The MYB182 Protein Down-Regulates Proanthocyanidin and Anthocyanin Biosynthesis in Poplar by Repressing Both Structural and Regulatory Flavonoid Genes

2015

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Trees in the genus Populus (poplar) contain phenolic secondary metabolites including the proanthocyanidins (PAs), which help to adapt these widespread trees to diverse environments. The transcriptional activation of PA biosynthesis in response to herbivory and ultraviolet light stress has been documented in poplar leaves, and a regulator of this process, the R2R3-MYB transcription factor MYB134, has been identified. MYB134-overexpressing transgenic plants show a strong high-PA phenotype. Analysis of these transgenic plants suggested the involvement of additional MYB transcription factors, including repressor-like MYB factors. Here, MYB182, a subgroup 4 MYB factor, was found to act as a negative regulator of the flavonoid pathway. Overexpression of MYB182 in hairy root culture and whole poplar plants led to reduced PA and anthocyanin levels as well as a reduction in the expression of key flavonoid genes. Similarly, a reduced accumulation of transcripts of a MYB PA activator and a basic helix-loop-helix cofactor was observed in MYB182-overexpressing hairy roots. Transient promoter activation assays in poplar cell culture demonstrated that MYB182 can disrupt transcriptional activation by MYB134 and that the basic helix-loop-helix-binding motif of MYB182 was essential for repression. Microarray analysis of transgenic plants demonstrated that down-regulated targets of MYB182 also include shikimate pathway genes. This work shows that MYB182 plays an important role in the fine-tuning of MYB134-mediated flavonoid metabolism.

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Section: Myb182 Is a Repressor That Reduces Pa And Anthocyanin Accumumentioning

confidence: 99%

The MYB182 Protein Down-Regulates Proanthocyanidin and Anthocyanin Biosynthesis in Poplar by Repressing Both Structural and Regulatory Flavonoid Genes

2015

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“…Two additional diVerentially expressed PPOs, PtdPPO2 and PtdPPO3, were later characterized in hybrid poplar and found to be expressed in stems and roots (Wang and Constabel 2004b). Populus is an excellent system for research on PPOs as the genus contains a broad array of phenolic compounds which could interact with PPOs (Constabel and Lindroth 2010). Salicinbased phenolic glycosides and proanthocyanidins (condensed tannins) together can constitute nearly one-third of poplar leaf dry mass and both are considered ecologically signiWcant compounds (Lindroth and Hwang 1996;Whitham et al 2006).…”

Section: Introductionmentioning

confidence: 99%

The polyphenol oxidase gene family in poplar: phylogeny, differential expression and identification of a novel, vacuolar isoform

Tran

Constabel

2011

Planta

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Polyphenol oxidases (PPOs) are oxidative enzymes that convert monophenols and o-diphenols to o-quinones using molecular oxygen. The quinone products are highly reactive following tissue damage and can interact with cellular constituents and cause oxidative browning and cross-linking. The induction of PPO in some plants as a result of wounding, herbivore attack, or pathogen infection has implicated them in defense. However, PPO-like enzymes that act as specific hydroxylases, for example in lignan and pigment biosynthesis, have also been discovered. Here, we present the first genome-enabled analysis of a PPO gene family. The Populus trichocarpa genome was found to contain a minimum of nine complete PPO genes, and seven of these were characterized further. The PPO gene family includes both recently duplicated and divergent sequences that are 36-98% identical at the amino acid level. Gene expression profiling in poplar tissues and organs revealed that the PPO genes are all differentially expressed during normal development, but that only a small subset of PPO genes are significantly upregulated by wounding, methyl jasmonate or pathogen infection. Our studies also identified PtrPPO13, a novel PPO gene that is predicted to encode an N-terminal signal peptide. Transient expression of green fluorescent protein fusions demonstrated its localization to the vacuolar lumen. Together, our findings show that the poplar PPO family is diverse and is likely linked to diverse physiological functions.

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“…Both natural genotypic variation and environmental factors influence tannin production, causing proanthocyanidin content to vary in natural poplar populations (Mansfield et al, 1999; Lindroth et al, 2002; Constabel and Lindroth, 2010). Even the highest tannin levels found in this experiment fell within the natural range of variation observed in forests (Preston et al, 2009a, b).…”

Section: Discussionmentioning

confidence: 99%

“…The tannins found in the leaf litter of poplars significantly influence decomposition and other soil processes (Mansfield, 1999; Schweitzer et al, 2004; Madritch et al, 2006). Tannin levels in poplar are variable but genetically determined, and are implicated in diverse ecological adaptations including defense against pests and pathogens, as well as other stress responses (Witham et al, 2006; Constabel and Lindroth, 2010). Many tannins have antimicrobial properties (Scalbert, 1991); in poplar, they may defend against fungal pathogens (Miranda et al, 2007; Holeski et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

The effects of high-tannin leaf litter from transgenic poplars on microbial communities in microcosm soils

Winder¹,

Lamarche²,

Constabel³

et al. 2013

Front. Microbiol.

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The Impact of Genomics on Advances in Herbivore Defense and Secondary Metabolism in Populus

Cited by 24 publications

References 103 publications

The MYB182 Protein Down-Regulates Proanthocyanidin and Anthocyanin Biosynthesis in Poplar by Repressing Both Structural and Regulatory Flavonoid Genes

The MYB182 Protein Down-Regulates Proanthocyanidin and Anthocyanin Biosynthesis in Poplar by Repressing Both Structural and Regulatory Flavonoid Genes

The polyphenol oxidase gene family in poplar: phylogeny, differential expression and identification of a novel, vacuolar isoform

The effects of high-tannin leaf litter from transgenic poplars on microbial communities in microcosm soils

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