Contrasting nitrogen fertilization treatments impact xylem gene expression and secondary cell wall lignification in Eucalyptus

Abstract

BackgroundNitrogen (N) is a main nutrient required for tree growth and biomass accumulation. In this study, we analyzed the effects of contrasting nitrogen fertilization treatments on the phenotypes of fast growing Eucalyptus hybrids (E. urophylla x E. grandis) with a special focus on xylem secondary cell walls and global gene expression patterns.ResultsHistological observations of the xylem secondary cell walls further confirmed by chemical analyses showed that lignin was reduced by luxuriant fertilization, whereas a consistent lignin deposition was observed in trees grown in N-limiting conditions. Also, the syringyl/guaiacyl (S/G) ratio was significantly lower in luxuriant nitrogen samples. Deep sequencing RNAseq analyses allowed us to identify a high number of differentially expressed genes (1,469) between contrasting N treatments. This number is dramatically higher than those obtained in similar studies performed in poplar but using microarrays. Remarkably, all the genes involved the general phenylpropanoid metabolism and lignin pathway were found to be down-regulated in response to high N availability. These findings further confirmed by RT-qPCR are in agreement with the reduced amount of lignin in xylem secondary cell walls of these plants.ConclusionsThis work enabled us to identify, at the whole genome level, xylem genes differentially regulated by N availability, some of which are involved in the environmental control of xylogenesis. It further illustrates that N fertilization can be used to alter the quantity and quality of lignocellulosic biomass in Eucalyptus, offering exciting prospects for the pulp and paper industry and for the use of short coppices plantations to produce second generation biofuels.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0256-9) contains supplementary material, which is available to authorized users.

Genome‐wide analysis of the lignin toolbox of Eucalyptus grandis

“…() and Camargo et al . (). Transcript abundance was assessed by microfluid qPCR using the BioMark ® 96.96 Dynamic Array platform (Fluidigm, San Francisco, CA, USA) as explained in Cassan‐Wang et al .…”

“…We also included stems, leaves and roots of young eucalypt trees subjected to cold treatments. Plant material description, RNA extraction and cDNA synthesis were previously reported in Cassan- Wang et al (2012), Soler et al (2014) and Camargo et al (2014). Transcript abundance was assessed by microfluid qPCR using the BioMark ® 96.96 Dynamic Array platform (Fluidigm, San Francisco, CA, USA) as explained in Cassan- Wang et al (2012).…”

Unravelling the Roles of Nitrogen Nutrition in Plant Disease Defences

“…The negative correlation between plant N status and surface wax density was demonstrated in both Pinus Palustris and Norway spruce seedlings [53,54]. Further, use of histochemical staining, biochemical assays and gene expression patterns have consistently demonstrated the negative impact of increased N availability on the degree of lignification of woody plant tissues [55,56]. Delayed lignin deposition on the xylem cell wall was observed when plants are exposed to excess N input [56].…”

A systems biology view of wood formation in Eucalyptus grandis trees submitted to different potassium and water regimes

“…Recent studies have highlighted the importance of a dynamic cross‐talk between the regulation of SCWs during development and in response to stresses, which is probably necessary to promote adaptation to environmental changes (Zinkgraf et al ., ). For instance, changes in the thickness, composition and/or structure of SCWs have been observed in response to several stresses such as nitrogen excess or depletion (Camargo et al ., ; Euring et al ., ), mechanical stress (Mellerowicz & Gorshkova, ) or low temperature (Ployet et al ., ). Transcription factors (TFs) involved in the regulation of SCW formation as well as SCW biosynthesis genes were reported to be induced by environmental constraints such as high salinity or iron deprivation in Arabidopsis (Taylor‐Teeples et al ., ) or cold stress in Eucalyptus (Ployet et al ., ).…”