Volume 5 Supplement 7
Regulatory network in lignin biosynthetic pathway through small RNAs in Acacia mangium: implications to the pulp and paper industry
© Ong and Wickneswari; licensee BioMed Central Ltd. 2011
Published: 13 September 2011
Lignin, after cellulose, is the second most abundant biopolymer accounting for approximately 15-35% of the dry weight of wood. As an important component of wood, lignin is indispensable for plant structure and defense. However, it is an undesirable component in the pulp and paper industry. Removal of lignin from cellulose is a costly and environmentally hazardous process. Tremendous efforts have been devoted to understand the role of enzymes and genes controlling the amount and composition of lignin to be deposited in the cell wall. However, studies on the impact of downregulation and overexpression of monolignol biosynthesis genes in model species on lignin content, plant fitness and viability have been inconsistent. Recently, non-coding RNAs have been discovered to play an important role in regulating the monolignol biosynthesis pathway genes [1–3]. Non-coding RNAs represent an emerging class of riboregulators, which are processed to shorter miRNAs or siRNAs. The current paradigm indicated that plant system use small RNAs (miRNAs and siRNAs) as guide for post-transcriptional gene silencing and epigenetic regulation. Although miRNAs and siRNAs result from different biogenesis pathways but both interact with target transcripts for direct cleavage or translation repression, effectively shutting down that genes’ functions. However, much less is known about the mechanism of gene regulation governed by these small RNAs in lignin biosynthesis pathway in A. mangium.
Total Counts of the four selected highly conserved miRNA families isolated from secondary xylem of low lignin A. mangium 54 (Am54) and high lignin A. mangium 48 (Am48).
MYB Trabscription Factor
APETALA 2-LIKE transcription factor
From the sequence results, we concluded that A. mangium small RNAs consist of a set of 14 highly conserved miRNAs families found in plant miRNA database, 82 novel miRNAs and a large proportion of non-conserved small RNAs with low expression levels. Out of these 14 highly conserved miRNAs families, only four miRNAs families were selected for validation in compression wood and tension wood and their total relative counts between Am54 and Am48 are shown (Table 1). Although these four miRNAs belong to different families, all of them were up regulated in tension wood, a region composed entirely of cellulose. The results obtained can be used to better understand the roles of small RNAs and for the development of a gene constructs for silencing of specific genes involved in monolignol biosynthesis with minimal effect on plant fitness and viability.
Special appreciation to IUFRO Tree Biotechnology Conference 2011 organizing committee for awarding Ong Seong Siang a Student Travel Grant to attend this conference. The author wish to thank Gene Pool Sequencing Centre for small RNA library preparation, sequencing and bioinformatics analysis. This work was funded by Ministry of Science, Technology and Innovation, Government of Malaysia through eScience grant 05-01-02-SF1020.
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