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- Jokipii-Lukkari, Soile, et al.
(författare)
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Transcriptional Roadmap to Seasonal Variation in Wood Formation of Norway Spruce
- 2018
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Ingår i: Plant Physiology. - : American Society of Plant Biologists. - 0032-0889 .- 1532-2548. ; 176:4, s. 2851-2870
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal cues influence several aspects of the secondary growth of tree stems, including cambial activity, wood chemistry, and transition to latewood formation. We investigated seasonal changes in cambial activity, secondary cell wall formation, and tracheid cell death in woody tissues of Norway spruce (Picea abies) throughout one seasonal cycle. RNA sequencing was performed simultaneously in both the xylem and cambium/phloem tissues of the stem. Principal component analysis revealed gradual shifts in the transcriptomes that followed a chronological order throughout the season. A notable remodeling of the transcriptome was observed in the winter, with many genes having maximal expression during the coldest months of the year. A highly coexpressed set of monolignol biosynthesis genes showed high expression during the period of secondary cell wall formation as well as a second peak in midwinter. This midwinter peak in expression did not trigger lignin deposition, as determined by pyrolysis-gas chromatography/mass spectrometry. Coexpression consensus network analyses suggested the involvement of transcription factors belonging to the ASYMMETRIC LEAVES2/LATERAL ORGAN BOUNDARIES and MYELOBLASTOSIS-HOMEOBOX families in the seasonal control of secondary cell wall formation of tracheids. Interestingly, the lifetime of the latewood tracheids stretched beyond the winter dormancy period, correlating with a lack of cell death-related gene expression. Our transcriptomic analyses combined with phylogenetic and microscopic analyses also identified the cellulose and lignin biosynthetic genes and putative regulators for latewood formation and tracheid cell death in Norway spruce, providing a toolbox for further physiological and functional assays of these important phase transitions.
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| 2. |
- Lin, Yao-Cheng, et al.
(författare)
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Functional and evolutionary genomic inferences in Populus through genome and population sequencing of American and European aspen
- 2018
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 115:46, s. E10970-E10978
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Tidskriftsartikel (refereegranskat)abstract
- The Populus genus is one of the major plant model systems, but genomic resources have thus far primarily been available for poplar species, and primarily Populus trichocarpa (Torr. & Gray), which was the first tree with a whole-genome assembly. To further advance evolutionary and functional genomic analyses in Populus, we produced genome assemblies and population genetics resources of two aspen species, Populus tremula L. and Populus tremuloides Michx. The two aspen species have distributions spanning the Northern Hemisphere, where they are keystone species supporting a wide variety of dependent communities and produce a diverse array of secondary metabolites. Our analyses show that the two aspens share a similar genome structure and a highly conserved gene content with P. trichocarpa but display substantially higher levels of heterozygosity. Based on population resequencing data, we observed widespread positive and negative selection acting on both coding and noncoding regions. Furthermore, patterns of genetic diversity and molecular evolution in aspen are influenced by a number of features, such as expression level, coexpression network connectivity, and regulatory variation. To maximize the community utility of these resources, we have integrated all presented data within the PopGenIE web resource (PopGenIE.org).
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| 3. |
- Ratke, Christine, et al.
(författare)
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Downregulating aspen xylan biosynthetic GT43 genes in developing wood stimulates growth via reprograming of the transcriptome
- 2018
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 219:1, s. 230-245
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Tidskriftsartikel (refereegranskat)abstract
- Xylan is one of the main compounds determining wood properties in hardwood species. The xylan backbone is thought to be synthesized by a synthase complex comprising two members of the GT43 family. We downregulated all GT43 genes in hybrid aspen (Populus tremulaxtremuloides) to understand their involvement in xylan biosynthesis.All three clades of the GT43 family were targeted for downregulation using RNA interference individually or in different combinations, either constitutively or specifically in developing wood.Simultaneous downregulation in developing wood of the B (IRX9) and C (IRX14) clades resulted in reduced xylan Xyl content relative to reducing end sequence, supporting their role in xylan backbone biosynthesis. This was accompanied by a higher lignocellulose saccharification efficiency. Unexpectedly, GT43 suppression in developing wood led to an overall growth stimulation, xylem cell wall thinning and a shift in cellulose orientation. Transcriptome profiling of these transgenic lines indicated that cell cycling was stimulated and secondary wall biosynthesis was repressed. We suggest that the reduced xylan elongation is sensed by the cell wall integrity surveying mechanism in developing wood.Our results show that wood-specific suppression of xylan-biosynthetic GT43 genes activates signaling responses, leading to increased growth and improved lignocellulose saccharification.
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