Eucalyptus species constitutes the most widely planted hardwood trees in temperate and subtropical regions. In this study, we compared the transcript levels of genes involved in lignocellulose formation such as cellulose, hemicellulose and lignin biosynthesis in two selected 3-year old hybrid Eucalyptus (Eucalyptus urophylla × Eucalyptus grandis) genotypes (AM063 and AM380) that have different lignin content. AM063 and AM380 had 20.2 and 35.5% of Klason lignin content and 59.0 and 48.2%, α-cellulose contents, respectively. We investigated the correlation between wood properties and transcript levels of wood formation-related genes using RNA-seq with total RNAs extracted from developing xylem tissues at a breast height. Transcript levels of cell wall construction genes such as cellulose synthase (CesA) and sucrose synthase (SUSY) were almost the same in both genotypes. However, AM063 exhibited higher transcript levels of UDP-glucose pyrophosphorylase and xyloglucan endotransglucoxylase than those in AM380. Most monolignol biosynthesis-related isozyme genes showed higher transcript levels in AM380. These results indicate monolignol biosynthesis-related genes may regulate wood composition in Eucalyptus. Flavonoids contents were also observed at much higher levels in AM380 as a result of the elevated transcript levels of common phenylpropanoid pathway genes, phenylalanine ammonium lyase, cinnamate-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL). Secondary plant cell wall formation is regulated by many transcription factors. We analyzed genes encoding NAC, WRKY, AP2/ERF, and KNOX transcription factors and found higher transcript levels of these genes in AM380. We also observed increased transcription of some MYB and LIM domain transcription factors in AM380 compared to AM063. All these results show that genes related to monolignol biosynthesis may regulate the wood composition and help maintain the ratio of cellulose and lignin contents in Eucalyptus plants.
Amapa Florestal e Celulose S. A. (AMCEL) , with the total area of 3 0 0, 0 0 0ha in Amapa state located in northern Brazil, operates eucalyptus plantation and wood chip production. AMCEL has outstanding features of flat and large bundled land, the distance to the chip mill and the port, abundant precipitation and warm climate. However, AMCEL could not make the most of these features because the growth of trees of plantation was not very good. After the purchase of AMCEL in December2 0 0 6, AMCEL has started the original selection and breeding program. As a result of continuous practice of the program, the growth of the trees was greatly improved.The author stationed in AMCEL from2 0 0 9to2 0 1 2as a supervisor of Research Department and had been working on the improvement of tree growth and property through tree breeding program. In this report the business summary of AMCEL will be presented. Then the relationship between tree growth and the tree property of clonal forest, such as KP yield and wood basic density measured by rapid analyses method, will be discussed.
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