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Fructan synthesis, accumulation, and polymer traits. I. Festulolium chromosome substitution lines.

Gallagher JA, Cairns AJ, Thomas D, Charlton A, Williams P, Turner LB - Front Plant Sci (2015)

Bottom Line: The fructans found as storage carbohydrates in temperate forage grasses have a physiological role in regrowth and stress tolerance.This included the presence of some very large polymers.There were indications that major genes involved in the control of some of these traits might be located on fescue chromosome 3 opening the possibility to develop grasses optimized for specific applications.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University Aberystwyth, UK.

ABSTRACT
The fructans found as storage carbohydrates in temperate forage grasses have a physiological role in regrowth and stress tolerance. They are also important for the nutritional value of fresh and preserved livestock feeds, and are potentially useful as feedstocks for biorefining. Seasonal variation in fructan content and the capacity for de novo fructan synthesis have been examined in a Festulolium monosomic substitution line family to investigate variation in the polymers produced by grasses in the ryegrass-fescue complex. There were significant differences between ryegrass and fescue. Fescue had low polymeric fructan content and a high oligomer/polymer ratio; synthesis of polymers longer than degree of polymerization 6 (DP6) from oligomers was slow. However, extension of polymer length from DP10/DP20 upward appeared to occur relatively freely, and, unlike ryegrass, fescue had a relatively even spread of polymer chain lengths above DP20. This included the presence of some very large polymers. Additionally fescue retained high concentrations of fructan, both polymeric and oligomeric, during conditions of low source/high sink demand. There were indications that major genes involved in the control of some of these traits might be located on fescue chromosome 3 opening the possibility to develop grasses optimized for specific applications.

No MeSH data available.


Related in: MedlinePlus

HPAEC chromatograms for (A) the Meltra ryegrass parent and (B) the fescue parent plant for retention times between 25 and 35 min. Insets show the regression of peak height on polymer chain length for DP20 to DP50.
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Figure 3: HPAEC chromatograms for (A) the Meltra ryegrass parent and (B) the fescue parent plant for retention times between 25 and 35 min. Insets show the regression of peak height on polymer chain length for DP20 to DP50.

Mentions: The capacity to synthesize fructan de novo from sucrose was tested with the excised leaf induction system. Leaf carbohydrate content was initially depleted by 7 days at low light and there was considerable variation between lines in the capacity to retain fructan under conditions where photosynthesis was considerably reduced (Table 3). Fructan retention was significantly higher (P < 0.05) in fescue and chromosome substitution line C3, and lower in most other lines. Liprior retained a high proportion of total fructan as oligofructan. There was little or no sucrose or monosaccharide present and the leaves were considered uninduced. Fructan synthesis was performed with exogenously supplied sucrose in the light to ensure no limitation of sucrose supply even if plants had low photosynthetic capacity as well as full expression of all light-induced genes. As the quantity of fructan synthesized never exceeded 35% of combined assimilation and uptake of sucrose (leaf sucrose content at t = 24 h), it is unlikely that any limitation of carbon supply occurred during the experiment. Fescue showed low fructan synthetic capacity, and particularly low conversion of oligomer into polymer (Table 4), but this low conversion rate was not seen in any of the chromosome substitution lines. Chromosome substitution lines C1 and C6 had lower synthetic rates than lines C3 and C7. Information on the relative distribution of different chain lengths in the high molecular weight fructan fraction was assessed from the pattern of polymer peaks in the range from DP 10 upward on the HPAEC chromatograms. The major polymer in this range was DP 20 for all lines (Table 4). There were obvious differences in the distribution of polymers in the range DP 20–DP 50. The derived relationship of peak height to DP (calculated from retention time; Supplementary Figure S2) was used to characterize a polymer-size profile for each line. There was variation for both profile regression constant and profile slope as illustrated by the contrasting data for the Meltra ryegrass parent and the fescue parent shown on Figure 3. Parallel curve analysis with the MLP 3.08 confirmed there were significant differences (P < 0.001) between lines for both parameters (Table 4). Based on pair-wise tests, fescue had a smaller profile regression slope and constant than ryegrass (P < 0.05). The F1 hybrid was intermediate with a significantly different profile constant (P < 0.05) from fescue and both ryegrass parents and a significantly different slope (P < 0.05) from fescue and Meltra. Chromosome substitution lines C1 and C6 had high regression constants similar to the ryegrass parents and significantly different (P < 0.05) from both lines C2 and C3. The regression slope of chromosome substitution lines C2 and C3 was significantly lower (P < 0.05) than line C1, indicating a relatively high proportion of very large polymers as in the fescue parent. Although there may have been variation in the largest polymer formed during the 24 h synthetic period it was not possible to test this from the data (Table 4).


Fructan synthesis, accumulation, and polymer traits. I. Festulolium chromosome substitution lines.

Gallagher JA, Cairns AJ, Thomas D, Charlton A, Williams P, Turner LB - Front Plant Sci (2015)

HPAEC chromatograms for (A) the Meltra ryegrass parent and (B) the fescue parent plant for retention times between 25 and 35 min. Insets show the regression of peak height on polymer chain length for DP20 to DP50.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495318&req=5

Figure 3: HPAEC chromatograms for (A) the Meltra ryegrass parent and (B) the fescue parent plant for retention times between 25 and 35 min. Insets show the regression of peak height on polymer chain length for DP20 to DP50.
Mentions: The capacity to synthesize fructan de novo from sucrose was tested with the excised leaf induction system. Leaf carbohydrate content was initially depleted by 7 days at low light and there was considerable variation between lines in the capacity to retain fructan under conditions where photosynthesis was considerably reduced (Table 3). Fructan retention was significantly higher (P < 0.05) in fescue and chromosome substitution line C3, and lower in most other lines. Liprior retained a high proportion of total fructan as oligofructan. There was little or no sucrose or monosaccharide present and the leaves were considered uninduced. Fructan synthesis was performed with exogenously supplied sucrose in the light to ensure no limitation of sucrose supply even if plants had low photosynthetic capacity as well as full expression of all light-induced genes. As the quantity of fructan synthesized never exceeded 35% of combined assimilation and uptake of sucrose (leaf sucrose content at t = 24 h), it is unlikely that any limitation of carbon supply occurred during the experiment. Fescue showed low fructan synthetic capacity, and particularly low conversion of oligomer into polymer (Table 4), but this low conversion rate was not seen in any of the chromosome substitution lines. Chromosome substitution lines C1 and C6 had lower synthetic rates than lines C3 and C7. Information on the relative distribution of different chain lengths in the high molecular weight fructan fraction was assessed from the pattern of polymer peaks in the range from DP 10 upward on the HPAEC chromatograms. The major polymer in this range was DP 20 for all lines (Table 4). There were obvious differences in the distribution of polymers in the range DP 20–DP 50. The derived relationship of peak height to DP (calculated from retention time; Supplementary Figure S2) was used to characterize a polymer-size profile for each line. There was variation for both profile regression constant and profile slope as illustrated by the contrasting data for the Meltra ryegrass parent and the fescue parent shown on Figure 3. Parallel curve analysis with the MLP 3.08 confirmed there were significant differences (P < 0.001) between lines for both parameters (Table 4). Based on pair-wise tests, fescue had a smaller profile regression slope and constant than ryegrass (P < 0.05). The F1 hybrid was intermediate with a significantly different profile constant (P < 0.05) from fescue and both ryegrass parents and a significantly different slope (P < 0.05) from fescue and Meltra. Chromosome substitution lines C1 and C6 had high regression constants similar to the ryegrass parents and significantly different (P < 0.05) from both lines C2 and C3. The regression slope of chromosome substitution lines C2 and C3 was significantly lower (P < 0.05) than line C1, indicating a relatively high proportion of very large polymers as in the fescue parent. Although there may have been variation in the largest polymer formed during the 24 h synthetic period it was not possible to test this from the data (Table 4).

Bottom Line: The fructans found as storage carbohydrates in temperate forage grasses have a physiological role in regrowth and stress tolerance.This included the presence of some very large polymers.There were indications that major genes involved in the control of some of these traits might be located on fescue chromosome 3 opening the possibility to develop grasses optimized for specific applications.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University Aberystwyth, UK.

ABSTRACT
The fructans found as storage carbohydrates in temperate forage grasses have a physiological role in regrowth and stress tolerance. They are also important for the nutritional value of fresh and preserved livestock feeds, and are potentially useful as feedstocks for biorefining. Seasonal variation in fructan content and the capacity for de novo fructan synthesis have been examined in a Festulolium monosomic substitution line family to investigate variation in the polymers produced by grasses in the ryegrass-fescue complex. There were significant differences between ryegrass and fescue. Fescue had low polymeric fructan content and a high oligomer/polymer ratio; synthesis of polymers longer than degree of polymerization 6 (DP6) from oligomers was slow. However, extension of polymer length from DP10/DP20 upward appeared to occur relatively freely, and, unlike ryegrass, fescue had a relatively even spread of polymer chain lengths above DP20. This included the presence of some very large polymers. Additionally fescue retained high concentrations of fructan, both polymeric and oligomeric, during conditions of low source/high sink demand. There were indications that major genes involved in the control of some of these traits might be located on fescue chromosome 3 opening the possibility to develop grasses optimized for specific applications.

No MeSH data available.


Related in: MedlinePlus