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Effects of PHENYLALANINE AMMONIA LYASE (PAL) knockdown on cell wall composition, biomass digestibility, and biotic and abiotic stress responses in Brachypodium.

Cass CL, Peraldi A, Dowd PF, Mottiar Y, Santoro N, Karlen SD, Bukhman YV, Foster CE, Thrower N, Bruno LC, Moskvin OV, Johnson ET, Willhoit ME, Phutane M, Ralph J, Mansfield SD, Nicholson P, Sedbrook JC - J. Exp. Bot. (2015)

Bottom Line: The cell walls of stems of BdPAL-knockdown plants had reductions of 43% in lignin and 57% in cell wall-bound ferulate, and a nearly 2-fold increase in the amounts of polysaccharide-derived carbohydrates released by thermochemical and hydrolytic enzymic partial digestion.RNA sequencing analyses revealed that the expression of genes associated with stress responses including ethylene biosynthesis and signalling were significantly altered in PAL knocked-down plants under non-challenging conditions.The data identify notable differences between the stress responses of these monocot pal mutants versus Arabidopsis (a dicot) pal mutants and provide insights into the challenges that may arise when deploying phenylpropanoid pathway-altered bioenergy crops.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Illinois State University, Normal, IL 61790 USA US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA.

No MeSH data available.


Related in: MedlinePlus

Bradi3g49250 (BdPAL1) and Bradi3g49260 (BdPAL2) transcript levels in Brachypodium CTL and BdPAL RNAi mutant tissues, and related protein activity. (A) Relative amounts of BdPAL1 and BdPAL2 transcripts in various CTL plant tissues, as determined by qRT–PCR. (B) BdPAL1 and BdPAL2 transcript levels in BdPAL RNA1-1 and 1-3 third internode stem tissues compared with the CTL. (C) Amounts of PAL activity (left three columns) and TAL activity (right three columns) in culm first internode extracts. Note that PAL activity is ~25-fold higher than TAL activity. In (A), means (represented by columns) were normalized to the first internode mean transcript level value, which was set to 1, using expression of BdUBC18 (Bradi4g00660) as reference. Bars represent standard deviations (SDs). Different letters above columns represent significant differences. n=4 biological reps and n=3 technical reps for (A) and (B), and 2 and 2 for (C).
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Figure 1: Bradi3g49250 (BdPAL1) and Bradi3g49260 (BdPAL2) transcript levels in Brachypodium CTL and BdPAL RNAi mutant tissues, and related protein activity. (A) Relative amounts of BdPAL1 and BdPAL2 transcripts in various CTL plant tissues, as determined by qRT–PCR. (B) BdPAL1 and BdPAL2 transcript levels in BdPAL RNA1-1 and 1-3 third internode stem tissues compared with the CTL. (C) Amounts of PAL activity (left three columns) and TAL activity (right three columns) in culm first internode extracts. Note that PAL activity is ~25-fold higher than TAL activity. In (A), means (represented by columns) were normalized to the first internode mean transcript level value, which was set to 1, using expression of BdUBC18 (Bradi4g00660) as reference. Bars represent standard deviations (SDs). Different letters above columns represent significant differences. n=4 biological reps and n=3 technical reps for (A) and (B), and 2 and 2 for (C).

Mentions: RNA sequencing (RNA-seq) analyses were performed to determine the relative expression levels of the eight putative BdPAL genes in stem plus leaf sheath tissues. As shown in Table 2, Bradi3g49250 and Bradi3g49260 were found to have transcript levels at least 24-fold higher than that of the next most highly expressed BdPAL gene, Bradi3g49280. Bradi3g49280 and Bradi5g15830 had modest transcript abundances in these tissues, whereas transcripts attributed to Bradi3g49270, Bradi3g48840, Bradi3g47110, and Bradi3g47120 were low or undetected. Quantitative reverse transcription–PCR (qRT–PCR) analysis was performed to determine relative expression levels of Bradi3g49250 and Bradi3g49260 across various tissues, revealing that these two genes were expressed in all tissues examined, with both being expressed at relatively high levels in stem internodes at all developmental stages (Fig. 1A). Bradi3g49250 transcript abundances were relatively low in leaf tissues, suggesting that Bradi3g49260 might play a more prominent role in leaves.


Effects of PHENYLALANINE AMMONIA LYASE (PAL) knockdown on cell wall composition, biomass digestibility, and biotic and abiotic stress responses in Brachypodium.

Cass CL, Peraldi A, Dowd PF, Mottiar Y, Santoro N, Karlen SD, Bukhman YV, Foster CE, Thrower N, Bruno LC, Moskvin OV, Johnson ET, Willhoit ME, Phutane M, Ralph J, Mansfield SD, Nicholson P, Sedbrook JC - J. Exp. Bot. (2015)

Bradi3g49250 (BdPAL1) and Bradi3g49260 (BdPAL2) transcript levels in Brachypodium CTL and BdPAL RNAi mutant tissues, and related protein activity. (A) Relative amounts of BdPAL1 and BdPAL2 transcripts in various CTL plant tissues, as determined by qRT–PCR. (B) BdPAL1 and BdPAL2 transcript levels in BdPAL RNA1-1 and 1-3 third internode stem tissues compared with the CTL. (C) Amounts of PAL activity (left three columns) and TAL activity (right three columns) in culm first internode extracts. Note that PAL activity is ~25-fold higher than TAL activity. In (A), means (represented by columns) were normalized to the first internode mean transcript level value, which was set to 1, using expression of BdUBC18 (Bradi4g00660) as reference. Bars represent standard deviations (SDs). Different letters above columns represent significant differences. n=4 biological reps and n=3 technical reps for (A) and (B), and 2 and 2 for (C).
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Related In: Results  -  Collection

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Figure 1: Bradi3g49250 (BdPAL1) and Bradi3g49260 (BdPAL2) transcript levels in Brachypodium CTL and BdPAL RNAi mutant tissues, and related protein activity. (A) Relative amounts of BdPAL1 and BdPAL2 transcripts in various CTL plant tissues, as determined by qRT–PCR. (B) BdPAL1 and BdPAL2 transcript levels in BdPAL RNA1-1 and 1-3 third internode stem tissues compared with the CTL. (C) Amounts of PAL activity (left three columns) and TAL activity (right three columns) in culm first internode extracts. Note that PAL activity is ~25-fold higher than TAL activity. In (A), means (represented by columns) were normalized to the first internode mean transcript level value, which was set to 1, using expression of BdUBC18 (Bradi4g00660) as reference. Bars represent standard deviations (SDs). Different letters above columns represent significant differences. n=4 biological reps and n=3 technical reps for (A) and (B), and 2 and 2 for (C).
Mentions: RNA sequencing (RNA-seq) analyses were performed to determine the relative expression levels of the eight putative BdPAL genes in stem plus leaf sheath tissues. As shown in Table 2, Bradi3g49250 and Bradi3g49260 were found to have transcript levels at least 24-fold higher than that of the next most highly expressed BdPAL gene, Bradi3g49280. Bradi3g49280 and Bradi5g15830 had modest transcript abundances in these tissues, whereas transcripts attributed to Bradi3g49270, Bradi3g48840, Bradi3g47110, and Bradi3g47120 were low or undetected. Quantitative reverse transcription–PCR (qRT–PCR) analysis was performed to determine relative expression levels of Bradi3g49250 and Bradi3g49260 across various tissues, revealing that these two genes were expressed in all tissues examined, with both being expressed at relatively high levels in stem internodes at all developmental stages (Fig. 1A). Bradi3g49250 transcript abundances were relatively low in leaf tissues, suggesting that Bradi3g49260 might play a more prominent role in leaves.

Bottom Line: The cell walls of stems of BdPAL-knockdown plants had reductions of 43% in lignin and 57% in cell wall-bound ferulate, and a nearly 2-fold increase in the amounts of polysaccharide-derived carbohydrates released by thermochemical and hydrolytic enzymic partial digestion.RNA sequencing analyses revealed that the expression of genes associated with stress responses including ethylene biosynthesis and signalling were significantly altered in PAL knocked-down plants under non-challenging conditions.The data identify notable differences between the stress responses of these monocot pal mutants versus Arabidopsis (a dicot) pal mutants and provide insights into the challenges that may arise when deploying phenylpropanoid pathway-altered bioenergy crops.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Illinois State University, Normal, IL 61790 USA US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA.

No MeSH data available.


Related in: MedlinePlus