Expression of a fungal ferulic acid esterase in suspension cultures of tall fescue (Festuca arundinacea) decreases cell wall feruloylation and increases rates of cell wall digestion

In the cell walls of grasses ferulic acid is esterified to arabinosyl residues in arabinoxylans that can then undergo oxidative coupling reactions to form ferulate dehydrodimers, trimers and oligomers which function to cross-link cell-wall polysaccharides, limiting cell wall degradability. Fungal ferulic acid esterase can release both esterified monomeric and dimeric ferulic acids from these cell wall arabinoxylans making the cell wall more susceptible to further enzymatic attack and increasing cell wall degradability. Non-embryogenic cell suspension cultures of Festuca arundinacea expressing a Aspergillus niger ferulic acid esterase (faeA) targeted to either the apoplast, or endoplasmic reticulum under the control of a constitutive actin promoter, or to the vacuole under the control of a soybean heat shock promoter, were established and FAE activity determined in the cells and medium during a growth cycle. Analysis of the ester-linked ferulates of the cell walls showed that all three transformed cell lines had both reduced ferulate levels and increased levels of xylanase mediated release of wall phenolics on autodigestion as well as increased rates of cell wall digestion in a simulated rumen environment, when compared to control non-transformed cells. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11240-017-1168-9) contains supplementary material, which is available to authorized users

Results of nodule detection along AUV track SO239_115-1_AUV9 (Abyss_175) during SONNE cruise SO239

Images were acquired by the DeepSurvey Camera on board GEOMAR's AUV Abyss. Nodules were delineated by the CoMoNoD algorithm [see related to references]. Result files are computed per AUV dive. Nodule detections below 5cm^2 are neglected as are detections above 707cm^2. Abundance statistics are computed per m^2 and gridded per m^2 as well. For overlapping images, max-pooling has been applied to select the values reported in the result files. Pixel values in the rendered maps correspond to the units reported in the ASCI files (median-nodule-size: cm^2, nodule-number: m^-2, percent-coverage: %, sorting, skewness and pixel-contributions are unit-free)

Comparison of growth of newly emerging third leaves of control and apoplast (T27 and T27R) or Golgi (T28 and T29) FAE expressing plants.

<p>Growth as increase in leaf length (A), distribution of growth within the elongation zone of leaf blades, determined as the relative segmental elongation rate (B), maximum daily extension rate (C), and leaf length at maximum extension rate (D). Mean ± SEM (n = 20–30 from each plant). Third leaves from tillers of 2–3 plants per line were measured until leaf length was constant. Letters indicate significant difference (Tukey’s, α = 0.05) among mean values.</p

Chlorophyll content of leaves of control and an FAE expressing plant (T27R) during leaf senescence.

<p>Chlorophyll content of leaves of control and an FAE expressing plant (T27R) during leaf senescence.</p

Ester linked HCAs in mature roots.

<p><i>p</i>-coumaric acid (A), ferulate monomers (B) and ferulate dimers (C). Ferulate monomers = trans- ferulic+ cis-ferulic acid. Ferulate dimers = 8-0-4’-diferulate + 5–5’ diferulate + 8-5cyclic diferulate (benzo form) + 8–5’-diferulate + an unknown ferulate dimer. Mean ± SEM (n = 2). Different letters indicate significant differences from the control (Tukey’s = 0.05).</p