Project description:The within-tree variation in wood properties constitutes an exceptional model to study the mechanisms that adjust the different biosynthetic pathways providing substrates with the massive and variable demands of different biosynthetic reactions of cell wall polymers. Although a few genes have been reported as differentially expressed in differentiating compression wood compared to normal or opposite wood, the expression of a larger set of genes is expected to change due the broad range of features that distinguish this reaction wood. By combining the construction of different cDNA libraries with microarray analyses, using samples from different Pinus pinaster provenances collected in different years and geographic locations, we have identified a total of 496 genes that change their expression during differentiation of compression wood (331 up-regulated and 165 down-regulated compared to opposite wood). Consistent with the well-known structural and chemical characteristics of compression wood, a large number of genes involved in the biosynthesis of cell wall components were shown to be up-regulated during compression wood differentiation, including genes involved in synthesis of cellulose, hemicellulose, lignin and lignans. In particular, further analysis of a set of these genes involved in providing S-adenosylmethionine, ammonium recycling, lignin and lignans biosynthesis showed parallel expression profiles to levels of lignin accumulation in cells undergoing xylogenesis in vivo and in vitro. The comparative transcriptomic analysis of compression and opposite wood formation in this work have revealed a broad spectrum of coordinated transcriptional modulation of biosynthetic reactions for different cell wall polymers associated to within-tree variations in softwood structure and composition. In particular, it suggest the occurrence of a mechanism that modulates at transcriptional level genes encoding enzymes involved in S-adenosylmethionine synthesis and ammonium assimilation with coniferyl alcohol demand for lignin and lignan synthesis, as a key metabolic requirement in cells undergoing lignification.

Project description:The within-tree variation in wood properties constitutes an exceptional model to study the mechanisms that adjust the different biosynthetic pathways providing substrates with the massive and variable demands of different biosynthetic reactions of cell wall polymers. Although a few genes have been reported as differentially expressed in differentiating compression wood compared to normal or opposite wood, the expression of a larger set of genes is expected to change due the broad range of features that distinguish this reaction wood. By combining the construction of different cDNA libraries with microarray analyses, using samples from different Pinus pinaster provenances collected in different years and geographic locations, we have identified a total of 496 genes that change their expression during differentiation of compression wood (331 up-regulated and 165 down-regulated compared to opposite wood). Consistent with the well-known structural and chemical characteristics of compression wood, a large number of genes involved in the biosynthesis of cell wall components were shown to be up-regulated during compression wood differentiation, including genes involved in synthesis of cellulose, hemicellulose, lignin and lignans. In particular, further analysis of a set of these genes involved in providing S-adenosylmethionine, ammonium recycling, lignin and lignans biosynthesis showed parallel expression profiles to levels of lignin accumulation in cells undergoing xylogenesis in vivo and in vitro. The comparative transcriptomic analysis of compression and opposite wood formation in this work have revealed a broad spectrum of coordinated transcriptional modulation of biosynthetic reactions for different cell wall polymers associated to within-tree variations in softwood structure and composition. In particular, it suggest the occurrence of a mechanism that modulates at transcriptional level genes encoding enzymes involved in S-adenosylmethionine synthesis and ammonium assimilation with coniferyl alcohol demand for lignin and lignan synthesis, as a key metabolic requirement in cells undergoing lignification. Two-condition experiment including dye-swap experiments, Compression Differentiating Xylem vs. Opposite Differentiating Xylem. Biological replicates: 4 compression xylem, 4 opposite xylew, harvested from four different individual pine trees. Two replicates per array.

Project description:The proper transition between the skotomorphogenic and photomorphogenic developmental programs is key for seedling survival and it is therefore tightly regulated. Besides light, which is the major cue that triggers this transition, several hormone pathways participate in this control, mainly antagonizing the light effect. Two of these hormones are gibberellins (GA) and brassinosteroids (BR). Both hormones promote the skotomorphogenesis and prevent photomorphogenesis, as evidenced by the partially de-etiolated phenotype caused by GA or BR deficiency, or by a blockage in the respective signaling pathways. We have previously shown that BR mediate GA activity in the control of this transition. For instance, treatment of dark-grown, GA-deficient seedlings with BRs was able to partially restore morphological phenotypes such as hypocotyl growth, and importantly to restore completely the molecular phenotype of CAB2 and RbcS gene expression. On the contrary, GA-treatment did not alter the same phenotypes in the BR deficient det2 mutant. Thus, the aim of this study was to investigate to what extent BRs mediate GA activity in dark-grown seedlings, and for that purpose we have the examined global changes in gene expression caused by treatment with GA and BRs in BR- and GA-deficient seedlings, respectively. We performed two sets of experiments, each one including three different samples. The first experiment included dark-grown, WT Col-0 mock-treated seedlings, or seedlings treated with either the GA biosynthesis inhibitor paclobutrazol (PAC) or with PAC+epibrassinolide (EBR). In this experiment, PAC samples were labelled with Cy3 and compared to WT and PAC+EBR samples, which were labelled with Cy5. Two biological repeast were performed. The second experiment included dark-grown, WT Col-0 seedlings and the det2-1 mutant, which was either mock-treated or treated with GA3. Two biological replicates were performed, in the first one the WT and det2-1+GA3 were labelled with Cy3 and the det2-1 sample with Cy5. The reverse labelling was used in the second replicate.

Dataset Information

Regulation of xylem fiber differentiation by gibberellins through DELLA-KNAT1 interaction

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