| 1. |
- Kucukoglu, Melis, et al.
(författare)
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CLE peptide signaling in plants-the power of moving around
- 2015
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 155, s. 74-87
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Tidskriftsartikel (refereegranskat)abstract
- The CLAVATA3 (CLV3)/EMBRYO SURROUNDING REGION (ESR)-RELATED (CLE) gene family encodes small secreted peptide ligands in plants. These peptides function non-cell autonomously through interactions with plasma membrane-associated LEUCINE-RICH REPEAT RECEPTOR-LIKE KINASEs (LRR-RLKs). These interactions are critical for cell-to-cell communications and control a variety of developmental and physiological processes in plants, such as regulation of stem cell proliferation and differentiation in the meristems, embryo and endosperm development, vascular development and autoregulation of nodulation. Here, we review the current knowledge in the field of CLE polypeptide signaling.
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| 2. |
- Kucukoglu, Melis
(författare)
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Molecular regulation of vascular cambium identity and activity
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In plants, secondary development and wood formation originates from the cell divisions within the vascular meristem, where the vascular stem cells are located. This thesis work presents my results on the molecular regulation of vascular cambium stem cell identity and activity. I have investigated the role of the receptor-like kinase PXC1 during vascular development in Arabidopsis thaliana. Mutant analysis revealed that in the absence of PXC1, plants display a pendant phenotype and reduced secondary cell wall thickening and lignification in the inflorescence stems, showing that PXC1 is an important regulator of secondary cell wall formation in Arabidopsis. I also participated in the characterization of members of the TDIF/CLE41/CLE44-TDR/PXY-WOX4 signaling module in hybrid aspen. Functional studies showed that knock down of PtWOX4 paralogs inhibits vascular cambium activity and secondary xylem formation in transgenic trees. Moreover, over-expression of PtCLE41A and related genes induces vascular patterning defects, highly associated with ectopic cambial activity. Results from transcriptional analysis suggested that PtCLE41A and related genes positively regulate PtWOX4 during the regulation of vascular cambium activity. By analysing gene expression patterns in Norway spruce, I provided evidence for the existence of conserved mechanisms in angiosperm and gymnosperm tree species with regard to the regulation of cambium function through CLE41, TDR/PXY and WOX4-like genes. Finally, I also identified different PtLCLE genes as candidate regulators of vascular cambium activity and tree growth. I studied functions of these genes by employing transgenic approaches in hybrid aspen and showed that down regulation or up regulation of these genes affect many different phenotypic properties in hybrid aspen such as cambium activity, internode elongation, leaf size, and adventitious rooting. In conclusion, results of these projects provide new insights into the regulation of vascular cambium activity and wood formation.
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| 3. |
- Kucukoglu, Melis, et al.
(författare)
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WUSCHEL-RELATED HOMEOBOX4 (WOX4)-like genes regulate cambial cell division activity and secondary growth in Populus trees
- 2017
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 215, s. 642-657
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Tidskriftsartikel (refereegranskat)abstract
- Plant secondary growth derives from the meristematic activity of the vascular cambium. In Arabidopsis thaliana, cell divisions in the cambium are regulated by the transcription factor WOX4, a key target of the CLAVATA3 (CLV3)/EMBRYO SURROUNDING REGION (ESR)-RELATED 41 (CLE41) signaling pathway. However, function of the WOX4-like genes in plants that are dependent on a much more prolific secondary growth, such as trees, remains unclear.Here, we investigate the role of WOX4 and CLE41 homologs for stem secondary growth in Populus trees.In Populus, PttWOX4 genes are specifically expressed in the cambial region during vegetative growth, but not after growth cessation and during dormancy, possibly involving a regulation by auxin. In PttWOX4a/b RNAi trees, primary growth was not affected whereas the width of the vascular cambium was severely reduced and secondary growth was greatly diminished.Our data show that in Populus trees, PttWOX4 genes control cell division activity in the vascular cambium, and hence growth in stem girth. This activity involves the positive regulation of PttWOX4a/b through PttCLE41-related genes. Finally, expression profiling suggests that the CLE41 signaling pathway is an evolutionarily conserved program for the regulation of vascular cambium activity between angiosperm and gymnosperm tree species.
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| 4. |
- Nystedt, Björn, et al.
(författare)
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The Norway spruce genome sequence and conifer genome evolution
- 2013
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 497:7451, s. 579-584
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Tidskriftsartikel (refereegranskat)abstract
- Conifers have dominated forests for more than 200 million years and are of huge ecological and economic importance. Here we present the draft assembly of the 20-gigabase genome of Norway spruce (Picea abies), the first available for any gymnosperm. The number of well-supported genes (28,354) is similar to the >100 times smaller genome of Arabidopsis thaliana, and there is no evidence of a recent whole-genome duplication in the gymnosperm lineage. Instead, the large genome size seems to result from the slow and steady accumulation of a diverse set of long-terminal repeat transposable elements, possibly owing to the lack of an efficient elimination mechanism. Comparative sequencing of Pinus sylvestris, Abies sibirica, Juniperus communis, Taxus baccata and Gnetum gnemon reveals that the transposable element diversity is shared among extant conifers. Expression of 24-nucleotide small RNAs, previously implicated in transposable element silencing, is tissue-specific and much lower than in other plants. We further identify numerous long (>10,000 base pairs) introns, gene-like fragments, uncharacterized long non-coding RNAs and short RNAs. This opens up new genomic avenues for conifer forestry and breeding.
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| 5. |
- Sundell, David, et al.
(författare)
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AspWood : High-Spatial-Resolution Transcriptome Profiles Reveal Uncharacterized Modularity of Wood Formation in Populus tremula
- 2017
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Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 29:7, s. 1585-1604
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Tidskriftsartikel (refereegranskat)abstract
- Trees represent the largest terrestrial carbon sink and a renewable source of ligno-cellulose. There is significant scope for yield and quality improvement in these largely undomesticated species, and efforts to engineer elite varieties will benefit from improved understanding of the transcriptional network underlying cambial growth and wood formation. We generated high-spatial-resolution RNA sequencing data spanning the secondary phloem, vascular cambium, and wood-forming tissues of Populus tremula. The transcriptome comprised 28,294 expressed, annotated genes, 78 novel protein-coding genes, and 567 putative long intergenic noncoding RNAs. Most paralogs originating from the Salicaceae whole-genome duplication had diverged expression, with the exception of those highly expressed during secondary cell wall deposition. Coexpression network analyses revealed that regulation of the transcriptome underlying cambial growth and wood formation comprises numerous modules forming a continuum of active processes across the tissues. A comparative analysis revealed that a majority of these modules are conserved in Picea abies. The high spatial resolution of our data enabled identification of novel roles for characterized genes involved in xylan and cellulose biosynthesis, regulators of xylem vessel and fiber differentiation and lignification. An associated web resource (AspWood, http://aspwood.popgenie.org) provides interactive tools for exploring the expression profiles and coexpression network.
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| 6. |
- Sundell, David, et al.
(författare)
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High-spatial-resolution transcriptome profiling reveals uncharacterized regulatory complexity underlying cambial growth and wood formation in Populus tremula
- 2016
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Trees represent the largest terrestrial carbon sink and a renewable source of ligno-cellulose. There is significant scope for yield and quality improvement in these largely undomesticated species, however, efforts to engineer new, elite varieties are constrained by the lack of a comprehensive understanding of the transcriptional network underlying cambial growth and wood formation. We generated RNA Sequencing transcriptome data for four mature, wild-growing aspens (Populus tremula) from high-spatial-resolution tangential cryosection series spanning the secondary phloem, vascular cambium, expanding and secondary cell wall forming xylem cells, cell death zone and the previous years annual ring. The transcriptome comprised 28,294 expressed, previously annotated protein-coding genes, 78 novel protein-coding genes and 567 long intergenic non-coding RNAs. Most paralogs originating from the Salicaceae whole genome duplication had diverged expression, with the notable exception of those with high expression during secondary cell wall deposition. We performed co-expression network analysis to identify central transcriptional modules and associated several of these with known biological processes. This revealed previously uncharacterized complexity underlying the regulation of cambial growth and wood formation, with modules forming a continuum of activated processes across the tissues. The high spatial resolution suggested novel roles for known genes involved in xylan and cellulose biosynthesis, regulators of xylem vessel and fiber differentiation and components of lignification. The associated web resource (AspWood, http://aspwood.popgenie.org) integrates the data within a set of interactive tools for exploring the co-expression network of cambial growth and wood formation.
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| 7. |
- Wang, Jiehua, et al.
(författare)
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The Arabidopsis LRR-RLK, PXC1, is a regulator of secondary wall formation correlated with the TDIF-PXY/TDR-WOX4 signaling pathway
- 2013
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Ingår i: BMC Plant Biology. - : Springer Science and Business Media LLC. - 1471-2229. ; 13, s. 94-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Although a number of leucine-rich repeat receptor-like kinase-encoding genes (LRR-RLKs) have been identified in plants, a functional role has been determined for only a few. Recent studies have demonstrated that an LRR-RLK, PXY/TDR, is important for the process of secondary vascular development. Other studies have indicated that PXY/TDR is unlikely to be the sole LRR-RLK involved in this complex process.Results: In this study, in silico analyses led to the identification of three Arabidopsis LRR-RLK genes (PXY-correlated; PXC1, 2, 3) with transcript accumulation profiles that correlated strongly with several key regulators of vascular development, including PXY/TDR, HB-8, REV, and CLE41. Expression profiling using qPCR and promoter: reporter lines indicated that all three PXC genes are associated with the vasculature. One in particular, PXC1 (At2g36570), had a strong correlation with PXY/TDR. Shifting pxc1 mutants from long-days to short-days showed that loss of the gene led to a dramatic reduction in secondary wall formation in xylem fibers. Transcript analysis of mutants for a variety of secondary cell wall-associated genes, including PXY/TDR indicated that the pathways mediated by PXC1 connect with those mediated by the TDIF-PXY/TDR-WOX4 system.Conclusions: The data indicate that the LRR-RLK, PXC1 is involved in secondary cell wall formation in xylem fibers. Whereas further study is needed to identify the ligands and mode of action of the PXC1 protein, it is clear from this work that similarly to the shoot apical meristem (SAM), secondary vascular development requires contributions from a number of LRR-RLKs.
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