Contrasting nitrogen fertilization treatments impact xylem gene expression and secondary cell wall lignification in EucalyptusReport as inadecuate




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BMC Plant Biology

, 14:256

Plant-abiotic interactions

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.

KeywordsEucalyptus Lignin Lignocellulosic biomass Nitrogen fertilization Wood RNA sequencing Abbreviations4CL4-Coumarate:CoA ligase

ADTArogenate dehydratase

C3Hp-coumarate 3-hydroxylase

C4HCinnamate-4-hydroxylase

CADCinnamyl alcohol dehydrogenase

CCoAOMTCaffeoyl-CoA O-methyltransferase

CCRHydroxycinnamoyl-CoA reductase

COMTCaffeate-5-hydroxyferulate O-methyltransferase

DEGDifferentially expressed genes

F5HFerulate 5-hydroxylase

FDHFormate Dehydrogenase

GOGATGlutamate synthase

GSGlutamine synthetase

HBHemoglobin

HCAHierarchical clustering analysis

HSPHeat shock proteins

LBDLateral organ boundary domain

NNitrogen

NiRNitrite reductase

NIRNear-infrared

NONitric oxide

NRNitrate reductase

NRTsNitrate transporters

PALPhenylalanine ammonia lyase

PCAPrincipal component analysis

qRT- PCRQuantitative reverse transcription-PCR

RPKMReads per kilobase of exons per million of fragments mapped

SCWSecondary cell wall

SEMScanning electron microscopy

S-GSyringyl-guaiacyl ratio

SHMTSerine Hydroxymethyltransferase 4

TFTranscription factor

UPM1Uroporphyrin III methyltransferase

Electronic supplementary materialThe online version of this article doi:10.1186-s12870-014-0256-9 contains supplementary material, which is available to authorized users.

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Author: Eduardo Leal Oliveira Camargo - Leandro Costa Nascimento - Marçal Soler - Marcela Mendes Salazar - Jorge Lepikson-Neto -

Source: https://link.springer.com/







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