As the most abundant renewable energy source , wood comprises the secondary cell wall (SCW). SCW biosynthesis involves lignin and cellulose deposition. Increasing studies have illustrated that R2R3-MYB transcription factors (TFs) play pivotal roles in affecting lignin accumulation and SCW formation. Nevertheless, the regulatory roles of R2R3-MYBs are still unresolved in Cryptomeria fortunei Hooibrenk cambium and wood formation. To dissect the potentials of CfMYBs , we successfully cloned and intensively studied the functions of CfMYB4 and CfMYB5 in SCW formation and abiotic stress response. They both contained the conserved MYB domain capable of forming a special structure that could bind to the core motifs of downstream genes. The phylogenetic tree implied that two CfMYBs clustered into different evolutionary branches. They were predominantly expressed in the stem and were localized to the nucleus. Furthermore, CfMYB4 functioned as an activator to enhance lignin and cellulose accumulation, and increase the SCW thickness by elevating the expression levels of SCW-related genes. By contrast, CfMYB5 negatively regulated lignin and cellulose biosynthesis, and decreased SCW formation by reducing the expression of SCW biosynthetic genes. Our data not only highlight the regulatory functions of CfMYBs in lignin deposition but also provide critical insights into the development of strategies for the genetic improvement of Cryptomeria fortunei wood biomass.
Jing Wang,Yumin Song,Futong Cui,Wenbin Wu,Haodong Zhu,Xiaoping Li,Kunyong Kang
In this paper, using Styphnolobium japonicum, Cryptomeria fortunei and Pinus yunnanensis as raw materials, cellulose (CE) was first extracted by chemical method (CM1) and biological enzymatic method 2 (BM2), and then further prepared into nanocellulose fiber (CNF) by biological enzymatic method 1(CPM (CPM stands for cellulase and pectinase)). The CE and CNF were characterized by FTIR, XRD, SEM, DSC and TG. The results showed that the CNF prepared by CM1-CPM was cellulose type II, CNF prepared by BM2-CPM was cellulose type I. The best crystallinity of the CNF prepared by CM1-CPM reached 74.1% (C. fortunei CNF), the best yield was 24.0% (S. japonicum CNF) and the minimum average diameter was 62.6 nm (C. fortunei CNF). However, the best crystallinity of CNF prepared by BM2-CPM reached 80.1% (C. fortunei CNF), the best yield was 27.4% (C. fortunei CNF), and the minimum average diameter was 31.6 nm (C. fortunei CNF). And also, the thermal degradation analysis of the CNF prepared from the three raw materials revealed that the CNF prepared by BM2-CPM had better thermal degradability. Finally, the thermal stability analysis of the C. fortunei CNF was carried out, and it was found that the residual mass of CNF prepared by BM2-CPM was 48%, while the residual mass of C. fortunei CNF prepared by BM1-CPM was 22%, which showed the C. fortunei CNF prepared by BM2-CPM had better thermal stability. Therefore, the properties of nanocellulose prepared by BM2-CPM are optimal.
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