| 1. |
- Plomion, Christophe, et al.
(author)
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Oak genome reveals facets of long lifespan
- 2018
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In: NATURE PLANTS. - : Springer Science and Business Media LLC. - 2055-026X .- 2055-0278. ; 4:7, s. 440-452
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Journal article (peer-reviewed)abstract
- Oaks are an important part of our natural and cultural heritage. Not only are they ubiquitous in our most common landscapes' but they have also supplied human societies with invaluable services, including food and shelter, since prehistoric times(2). With 450 species spread throughout Asia, Europe and America(3), oaks constitute a critical global renewable resource. The longevity of oaks (several hundred years) probably underlies their emblematic cultural and historical importance. Such long-lived sessile organisms must persist in the face of a wide range of abiotic and biotic threats over their lifespans. We investigated the genomic features associated with such a long lifespan by sequencing, assembling and annotating the oak genome. We then used the growing number of whole-genome sequences for plants (including tree and herbaceous species) to investigate the parallel evolution of genomic characteristics potentially underpinning tree longevity. A further consequence of the long lifespan of trees is their accumulation of somatic mutations during mitotic divisions of stem cells present in the shoot apical meristems. Empirical(4) and modelling(5) approaches have shown that intra-organismal genetic heterogeneity can be selected for(6) and provides direct fitness benefits in the arms race with short-lived pests and pathogens through a patchwork of intra-organismal phenotypes(7). However, there is no clear proof that large-statured trees consist of a genetic mosaic of clonally distinct cell lineages within and between branches. Through this case study of oak, we demonstrate the accumulation and transmission of somatic mutations and the expansion of disease-resistance gene families in trees.
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| 2. |
- Soler, Marçal, et al.
(author)
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The Eucalyptus linker histone variant EgH1.3 cooperates with the transcription factor EgMYB1 to control lignin biosynthesis during wood formation
- 2017
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In: New Phytologist. - : Wiley-Blackwell. - 0028-646X .- 1469-8137. ; 213:1, s. 287-299
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Journal article (peer-reviewed)abstract
- Wood, also called secondary xylem, is a specialized vascular tissue constituted by different cell types that undergo a differentiation process involving deposition of thick, lignified secondary cell walls. The mechanisms needed to control the extent of lignin deposition depending on the cell type and the differentiation stage are far from being fully understood. We found that the Eucalyptus transcription factor EgMYB1, which is known to repress lignin biosynthesis, interacts specifically with a linker histone variant, EgH1.3. This interaction enhances the repression of EgMYB1' s target genes, strongly limiting the amount of lignin deposited in xylem cell walls. The expression profiles of EgMYB1 and EgH1.3 overlap in xylem cells at early stages of their differentiation as well as in mature parenchymatous xylem cells, which have no or only thin lignified secondary cell walls. This suggests that a complex between EgMYB1 and EgH1.3 integrates developmental signals to prevent premature or inappropriate lignification of secondary cell walls, providing a mechanism to fine-tune the differentiation of xylem cells in time and space. We also demonstrate a role for a linker histone variant in the regulation of a specific developmental process through interaction with a transcription factor, illustrating that plant linker histones have other functions beyond chromatin organization.
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| 3. |
- Soler, Marçal, et al.
(author)
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The Woody-Preferential Gene EgMYB88 Regulates the Biosynthesis of Phenylpropanoid-Derived Compounds in Wood
- 2016
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In: Frontiers in Plant Science. - : Frontiers Media. - 1664-462X. ; 7
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Journal article (peer-reviewed)abstract
- Comparative phylogenetic analyses of the R2R3-MYB transcription factor family revealed that five subgroups were preferentially found in woody species and were totally absent from Brassicaceae and monocots (Soler et al., 2015). Here, we analyzed one of these subgroups (WPS-I) for which no gene had been yet characterized. Most Eucalyptus members of WPS-I are preferentially expressed in the vascular cambium, the secondary meristem responsible for tree radial growth. We focused on EgMYB88, which is the most specifically and highly expressed in vascular tissues, and showed that it behaves as a transcriptional activator in yeast. Then, we functionally characterized EgMYB88 in both transgenic Arabidopsis and poplar plants overexpressing either the native or the dominant repression form (fused to the Ethylene-responsive element binding factor-associated Amphiphilic Repression motif, EAR). The transgenic Arabidopsis lines had no phenotype whereas the poplar lines overexpressing EgMYB88 exhibited a substantial increase in the levels of the flavonoid catechin and of some salicinoid phenolic glycosides (salicortin, salireposide, and tremulacin), in agreement with the increase of the transcript levels of landmark biosynthetic genes. A change in the lignin structure (increase in the syringyl vs. guaiacyl, S/G ratio) was also observed. Poplar lines overexpressing the EgMYB88 dominant repression form did not show a strict opposite phenotype. The level of catechin was reduced, but the levels of the salicinoid phenolic glycosides and the S/G ratio remained unchanged. In addition, they showed a reduction in soluble oligolignols containing sinapyl p-hydroxybenzoate accompanied by a mild reduction of the insoluble lignin content. Altogether, these results suggest that EgMYB88, and more largely members of the WPS-I group, could control in cambium and in the first layers of differentiating xylem the biosynthesis of some phenylpropanoid-derived secondary metabolites including lignin.
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