Glycosylation-mediated phenylpropanoid partitioning in Populus tremuloides cell cultures

Abstract

BackgroundPhenylpropanoid-derived phenolic glycosides (PGs) and condensed tannins (CTs) comprise large, multi-purpose non-structural carbon sinks in Populus. A negative correlation between PG and CT concentrations has been observed in several studies. However, the molecular mechanism underlying the relationship is not known.ResultsPopulus cell cultures produce CTs but not PGs under normal conditions. Feeding salicyl alcohol resulted in accumulation of salicins, the simplest PG, in the cells, but not higher-order PGs. Salicin accrual reflected the stimulation of a glycosylation response which altered a number of metabolic activities. We utilized this suspension cell feeding system as a model for analyzing the possible role of glycosylation in regulating the metabolic competition between PG formation, CT synthesis and growth. Cells accumulated salicins in a dose-dependent manner following salicyl alcohol feeding. Higher feeding levels led to a decrease in cellular CT concentrations (at 5 or 10 mM), and a negative effect on cell growth (at 10 mM). The competition between salicin and CT formation was reciprocal, and depended on the metabolic status of the cells. We analyzed gene expression changes between controls and cells fed with 5 mM salicyl alcohol for 48 hr, a time point when salicin accumulation was near maximum and CT synthesis was reduced, with no effect on growth. Several stress-responsive genes were up-regulated, suggestive of a general stress response in the fed cells. Salicyl alcohol feeding also induced expression of genes associated with sucrose catabolism, glycolysis and the Krebs cycle. Transcript levels of phenylalanine ammonia lyase and most of the flavonoid pathway genes were reduced, consistent with down-regulated CT synthesis.ConclusionsExogenous salicyl alcohol was readily glycosylated in Populus cell cultures, a process that altered sugar utilization and phenolic partitioning in the cells. Using this system, we identified candidate genes for glycosyltransferases that may mediate the glycosylation, and for transporters that mediate the subcellular compartmentalization of sugars and phenolic glycosides. The suspension cells appear to represent a facile system for dissecting the regulation of phenolic carbon partitioning, and in turn, its effects on growth in Populus.

Early differentiation in biomass production and carbon sequestration of white poplar and its two hybrids in Central Iran

“…We evaluated the wood yield and carbon sequestration of the new hybrids for the first time in a semiarid and cold region. We recorded significant differences in yield between clones resulting from reciprocal crossing, a result reported for other hybrid poplars (Payyavula et al 2009;Stanton et al 2010;Kang et al 2000). We attribute the yield differences to genomic Early differentiation in biomass production and carbon sequestration 67 imprinting, which increased the possibility that paternally and maternally inherited wood production alleles would be differentially expressed in the new clones.…”

The sucrose transporter family in Populus: the importance of a tonoplast PtaSUT4 to biomass and carbon partitioning

“…Bark with phloem attached was peeled off of the stem, and a razorblade was used to scrape phloem from the inside of the bark, and xylem from the outer layers of the wood. Cell suspension culture (Payyavula et al. , 2009) and male and female flowers from Populus tremuloides Michx.…”

Metabolic profiling reveals altered sugar and secondary metabolism in response to UGPase overexpression in Populus

“…After quantifying RNA using NanoDrop, cDNA was prepared from 1500 ng total RNA. qRT-PCR was performed using 3 ng RNA equivalent cDNA, gene specific primers (200 nM) (primer sequences provided in Additional file 11 ) [ 48 ] and 1Z SYBR green (Bio-Rad life sciences, Hercules, CA) on the StepOnePlusTM Real-Time PCR system (Applied Biosystems, Grand Island, NY). Gene expression was calculated using ΔcT or ΔΔcT methods [ 49 ] based on the threshold cycle (cT) values of the target gene and the housekeeping genes, Ubiquitin-conjugating enzyme E2 (Potri.006G205700) and 18S ribosomal RNA (AF206999) (Additional file 11 ) .…”