Limits...
Conifer R2R3-MYB transcription factors: sequence analyses and gene expression in wood-forming tissues of white spruce (Picea glauca).

Bedon F, Grima-Pettenati J, Mackay J - BMC Plant Biol. (2007)

Bottom Line: The number and length of the introns in spruce MYB genes varied significantly, but their positions were well conserved relative to angiosperm MYB genes.Our survey of 18 conifer R2R3-MYB genes clearly showed a gene family structure similar to that of Arabidopsis.Three of the sequences are likely to play a role in lignin metabolism and/or wood formation in gymnosperm trees, including a close homolog of the loblolly pine PtMYB4, shown to regulate lignin biosynthesis in transgenic tobacco.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre d'étude de la Forêt, Université Laval, Pavillon Charles-Eugène Marchand, Sainte Foy G1K7P4, Québec, Canada. frank.bedon@rsvs.ulaval.ca

ABSTRACT

Background: Several members of the R2R3-MYB family of transcription factors act as regulators of lignin and phenylpropanoid metabolism during wood formation in angiosperm and gymnosperm plants. The angiosperm Arabidopsis has over one hundred R2R3-MYBs genes; however, only a few members of this family have been discovered in gymnosperms.

Results: We isolated and characterised full-length cDNAs encoding R2R3-MYB genes from the gymnosperms white spruce, Picea glauca (13 sequences), and loblolly pine, Pinus taeda L. (five sequences). Sequence similarities and phylogenetic analyses placed the spruce and pine sequences in diverse subgroups of the large R2R3-MYB family, although several of the sequences clustered closely together. We searched the highly variable C-terminal region of diverse plant MYBs for conserved amino acid sequences and identified 20 motifs in the spruce MYBs, nine of which have not previously been reported and three of which are specific to conifers. The number and length of the introns in spruce MYB genes varied significantly, but their positions were well conserved relative to angiosperm MYB genes. Quantitative RTPCR of MYB genes transcript abundance in root and stem tissues revealed diverse expression patterns; three MYB genes were preferentially expressed in secondary xylem, whereas others were preferentially expressed in phloem or were ubiquitous. The MYB genes expressed in xylem, and three others, were up-regulated in the compression wood of leaning trees within 76 hours of induction.

Conclusion: Our survey of 18 conifer R2R3-MYB genes clearly showed a gene family structure similar to that of Arabidopsis. Three of the sequences are likely to play a role in lignin metabolism and/or wood formation in gymnosperm trees, including a close homolog of the loblolly pine PtMYB4, shown to regulate lignin biosynthesis in transgenic tobacco.

Show MeSH

Related in: MedlinePlus

Transcript abundance for MYB genes and secondary cell-wall-related genes in differentiating secondary xylem and in primary growth (new flush) of spruce seedlings. Transcript abundance was determined as in Figure 4 for, a) 13 spruce MYB genes, and b) five cell-wall-related genes in differentiating secondary xylem from stem and in the elongating terminal leader (apical stem) from 3-year-old spruce seedlings. The standard error (bars) was calculated from three biological replicates and two independent technical repetitions (i.e. six independent measurements). PAL, phenylalanine ammonia lyase; 4CL, 4-coumarate: CoA ligase; CCOaOMT, caffeoyl-CoA 3-O-methyltransferase; AGP, arabinogalactan protein; CAD, cinnamyl alcohol dehydrogenase. NS, no PCR product detected.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC1851958&req=5

Figure 4: Transcript abundance for MYB genes and secondary cell-wall-related genes in differentiating secondary xylem and in primary growth (new flush) of spruce seedlings. Transcript abundance was determined as in Figure 4 for, a) 13 spruce MYB genes, and b) five cell-wall-related genes in differentiating secondary xylem from stem and in the elongating terminal leader (apical stem) from 3-year-old spruce seedlings. The standard error (bars) was calculated from three biological replicates and two independent technical repetitions (i.e. six independent measurements). PAL, phenylalanine ammonia lyase; 4CL, 4-coumarate: CoA ligase; CCOaOMT, caffeoyl-CoA 3-O-methyltransferase; AGP, arabinogalactan protein; CAD, cinnamyl alcohol dehydrogenase. NS, no PCR product detected.

Mentions: We also compared the abundance of the different MYB transcripts in the differentiating secondary xylem and in the elongating apical leader of young spruce trees (Fig. 4). The cell wall-related genes PAL, 4CL, CAD, CCoAOMT and an arabinogalactan protein (AGP) were included in this analysis. For these within tissue comparisons, the data were normalized against the EF1-α transcript levels. Again, the spruce MYB transcripts 2, 4 and 8 were clearly the most abundant among the MYBs detected in the secondary xylem, consistent with the data from the mature trees. In the apical leader, the relative abundance of the MYB transcripts was quite different than in the secondary xylem, except that PgMYB4 transcripts remained very abundant. Some MYB genes that were weakly expressed or not detectable in secondary xylem were among the most highly expressed in apical stem (PgMYB6, 7 and 11; Fig. 4a).


Conifer R2R3-MYB transcription factors: sequence analyses and gene expression in wood-forming tissues of white spruce (Picea glauca).

Bedon F, Grima-Pettenati J, Mackay J - BMC Plant Biol. (2007)

Transcript abundance for MYB genes and secondary cell-wall-related genes in differentiating secondary xylem and in primary growth (new flush) of spruce seedlings. Transcript abundance was determined as in Figure 4 for, a) 13 spruce MYB genes, and b) five cell-wall-related genes in differentiating secondary xylem from stem and in the elongating terminal leader (apical stem) from 3-year-old spruce seedlings. The standard error (bars) was calculated from three biological replicates and two independent technical repetitions (i.e. six independent measurements). PAL, phenylalanine ammonia lyase; 4CL, 4-coumarate: CoA ligase; CCOaOMT, caffeoyl-CoA 3-O-methyltransferase; AGP, arabinogalactan protein; CAD, cinnamyl alcohol dehydrogenase. NS, no PCR product detected.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1851958&req=5

Figure 4: Transcript abundance for MYB genes and secondary cell-wall-related genes in differentiating secondary xylem and in primary growth (new flush) of spruce seedlings. Transcript abundance was determined as in Figure 4 for, a) 13 spruce MYB genes, and b) five cell-wall-related genes in differentiating secondary xylem from stem and in the elongating terminal leader (apical stem) from 3-year-old spruce seedlings. The standard error (bars) was calculated from three biological replicates and two independent technical repetitions (i.e. six independent measurements). PAL, phenylalanine ammonia lyase; 4CL, 4-coumarate: CoA ligase; CCOaOMT, caffeoyl-CoA 3-O-methyltransferase; AGP, arabinogalactan protein; CAD, cinnamyl alcohol dehydrogenase. NS, no PCR product detected.
Mentions: We also compared the abundance of the different MYB transcripts in the differentiating secondary xylem and in the elongating apical leader of young spruce trees (Fig. 4). The cell wall-related genes PAL, 4CL, CAD, CCoAOMT and an arabinogalactan protein (AGP) were included in this analysis. For these within tissue comparisons, the data were normalized against the EF1-α transcript levels. Again, the spruce MYB transcripts 2, 4 and 8 were clearly the most abundant among the MYBs detected in the secondary xylem, consistent with the data from the mature trees. In the apical leader, the relative abundance of the MYB transcripts was quite different than in the secondary xylem, except that PgMYB4 transcripts remained very abundant. Some MYB genes that were weakly expressed or not detectable in secondary xylem were among the most highly expressed in apical stem (PgMYB6, 7 and 11; Fig. 4a).

Bottom Line: The number and length of the introns in spruce MYB genes varied significantly, but their positions were well conserved relative to angiosperm MYB genes.Our survey of 18 conifer R2R3-MYB genes clearly showed a gene family structure similar to that of Arabidopsis.Three of the sequences are likely to play a role in lignin metabolism and/or wood formation in gymnosperm trees, including a close homolog of the loblolly pine PtMYB4, shown to regulate lignin biosynthesis in transgenic tobacco.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre d'étude de la Forêt, Université Laval, Pavillon Charles-Eugène Marchand, Sainte Foy G1K7P4, Québec, Canada. frank.bedon@rsvs.ulaval.ca

ABSTRACT

Background: Several members of the R2R3-MYB family of transcription factors act as regulators of lignin and phenylpropanoid metabolism during wood formation in angiosperm and gymnosperm plants. The angiosperm Arabidopsis has over one hundred R2R3-MYBs genes; however, only a few members of this family have been discovered in gymnosperms.

Results: We isolated and characterised full-length cDNAs encoding R2R3-MYB genes from the gymnosperms white spruce, Picea glauca (13 sequences), and loblolly pine, Pinus taeda L. (five sequences). Sequence similarities and phylogenetic analyses placed the spruce and pine sequences in diverse subgroups of the large R2R3-MYB family, although several of the sequences clustered closely together. We searched the highly variable C-terminal region of diverse plant MYBs for conserved amino acid sequences and identified 20 motifs in the spruce MYBs, nine of which have not previously been reported and three of which are specific to conifers. The number and length of the introns in spruce MYB genes varied significantly, but their positions were well conserved relative to angiosperm MYB genes. Quantitative RTPCR of MYB genes transcript abundance in root and stem tissues revealed diverse expression patterns; three MYB genes were preferentially expressed in secondary xylem, whereas others were preferentially expressed in phloem or were ubiquitous. The MYB genes expressed in xylem, and three others, were up-regulated in the compression wood of leaning trees within 76 hours of induction.

Conclusion: Our survey of 18 conifer R2R3-MYB genes clearly showed a gene family structure similar to that of Arabidopsis. Three of the sequences are likely to play a role in lignin metabolism and/or wood formation in gymnosperm trees, including a close homolog of the loblolly pine PtMYB4, shown to regulate lignin biosynthesis in transgenic tobacco.

Show MeSH
Related in: MedlinePlus