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Invertase plays a crucial role in carbohydrate partitioning and plant development as it catalyses the irreversible hydrolysis of sucrose into glucose and fructose. The invertase family in plants is composed of two sub-families: acid invertases, which are targeted to the cell wall and vacuole; and neutral/alkaline invertases, which function in the cytosol. In this study, 5 cell wall invertase genes (PtCWINV1-5), 3 vacuolar invertase genes (PtVINV1-3) and 16 neutral/alkaline invertase genes (PtNINV1-16) were identified in the Populus genome and found to be distributed on 14 chromosomes. A comprehensive analysis of poplar invertase genes was performed, including structures, chromosome location, phylogeny, evolutionary pattern and expression profiles. Phylogenetic analysis indicated that the two sub-families were both divided into two clades. Segmental duplication is contributed to neutral/alkaline sub-family expansion. Furthermore, the Populus invertase genes displayed differential expression in roots, stems, leaves, leaf buds and in response to salt/cold stress and pathogen infection. In addition, the analysis of enzyme activity and sugar content revealed that invertase genes play key roles in the sucrose metabolism of various tissues and organs in poplar. This work lays the foundation for future functional analysis of the invertase genes in Populus and other woody perennials.

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Casuarina trees are planted along the coastal area of the South China as windbreaks, and in agroforestry systems and for wood and fuel wood production. At present, casuarina plantations cover about 300,000 hectares.Casuarina equisetifolia, C. cunninghamiana, C. glauca and C. junghuhniana are the most commonly planted species. A simple technique for the mass propagation of casuarina seedlings has been developed using cuttings rooted in water. A series of field trials have been carried with various Casuarina species, provenances and clones to screen for adaptability to biotic and abiotic stresses in different areas of China. Experiments conducted in the nursery, glasshouse and field showed that ectomycorrhizal (ECTM), arbuscular mycorrhizal (AM) fungi or Frankia symbiotic associations play an important role in improved growth of managed casuarina plantations.