Abstract
BackgroundGmelina arborea Roxb is a fast-growing tree species of commercial importance for tropical countries due to multiple industrial uses of its wood. Wood is primarily composed of thick secondary cell walls of xylem cells which imparts the strength to the wood. Identification of the genes involved in the secondary cell wall biosynthesis as well as their cognate regulators is crucial to understand how the production of wood occurs and serves as a starting point for developing breeding strategies to produce varieties with improved wood quality, better paper pulping or new potential uses such as biofuel production.In order to gain knowledge on the molecular mechanisms and gene regulation related with wood development in white teak, a de novo sequencing and transcriptome assembly approach was used employing secondary cell wall synthesizing cells from young white teak trees.ResultsFor generation of transcriptome, RNA-seq reads were assembled into 110,992 transcripts and 49,364 genes were functionally annotated using plant databases; 5071 GO terms and 25,460 SSR markers were identified within xylem transcripts and 10,256 unigenes were assigned to KEGG database in 130 pathways. Among transcription factor families, C2H2, C3H, bLHLH and MYB were the most represented in xylem. Differential gene expression analysis using leaves as a reference was carried out and a total of 20,954 differentially expressed genes were identified including monolignol biosynthetic pathway genes. The differential expression of selected genes (4CL, COMT, CCoAOMT, CCR and NST1) was validated using qPCR.ConclusionsWe report the very first de novo transcriptome of xylem-related genes in this tropical timber species of commercial importance and constitutes a valuable extension of the publicly available transcriptomic resource aimed at fostering both basic and breeding studies.
Highlights
Gmelina arborea Roxb is a fast-growing tree species of commercial importance for tropical countries due to multiple industrial uses of its wood
Generation and annotation of a reference xylem transcriptome RNA-seq of G. arborea xylem library resulted in approximately 165 million paired reads
Differential expression analysis evidenced that, in the case of leaves, various transcription factors, predominantly upregulated, were related to leaf development and photomorphogenesis processes such as KAN family members that have been related to the abaxial identity [44], MYB-like related to foliar senescence [45] and ELF3 related to development and flowering [46]
Summary
Gmelina arborea Roxb is a fast-growing tree species of commercial importance for tropical countries due to multiple industrial uses of its wood. Its introduction and excellent adaptation to the American tropics (Costa Rica, Venezuela, Colombia and Guatemala) is due to the traits like fast growth, high biomass production (20–25 m3/ha/year), less susceptibility to the local pests and high yields in addition to the versatility of its wood use which allow a faster investment return [6]. It is considered as a species of choice for both reforestation programs and agroforestry systems in these areas [6, 7]
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