Identification of a molecular marker associated with lignotuber in Eucalyptus ssp.

About 95% of Eucalyptus species present an organ known as a lignotuber, a basal woody swelling that holds a large number of dormant buds in a protected position along with carbohydrates and other nutrients. The importance of this trait in Eucalyptus species relates to its regenerative capacity, particularly in the context of coppicing practices and survival in regions of high abiotic stress, especially fire. In this study, we identified and characterized a genomic region associated with the lignotuber trait in commercially important Eucalyptus species by developing a polymorphic marker that co-segregates with lignotuber presence. The marker was then converted into a SCAR (Sequence Characterized Amplified Region) marker, validated in four other Eucalyptus species and hybrids and analyzed in silico. Our investigation presents a marker (ELig) that is effective in identifying individuals with lignotuber. In silico and Southern blot analyses show that the marker is present in a single copy region and is related to auxilin/cyclin-G associated kinase, containing a DnaJ domain. The ELig marker is an important tool that can be used to manage crosses in Eucalyptus breeding programs and inform studies involving lignotuber development and genetics.

Diversity of endophytic bacteria from Eucalyptus species seeds and colonization of seedlings by Pantoea agglomerans.

The diversity and beneficial characteristics of endophytic microorganisms have been studied in several host plants. However, information regarding naturally occurring seed-associated endophytes and vertical transmission among different life-history stages of hosts is limited. Endophytic bacteria were isolated from seeds and seedlings of 10 Eucalyptus species and two hybrids. The results showed that endophytic bacteria, such as Bacillus, Enterococcus, Paenibacillus and Methylobacterium, are vertically transferred from seeds to seedlings. In addition, the endophytic bacterium Pantoea agglomerans was tagged with the gfp gene, inoculated into seeds and further reisolated from seedlings. These results suggested a novel approach to change the profile of the plants, where the bacterium is a delivery vehicle for desired traits. This is the first report of an endophytic bacterial community residing in Eucalyptus seeds and the transmission of these bacteria from seeds to seedlings. The bacterial species reported in this work have been described as providing benefits to host plants. Therefore, we suggest that endophytic bacteria can be transmitted vertically from seeds to seedlings, assuring the support of the bacterial community in the host plant.

SAGE transcript profiling of the juvenile cambial region of Eucalyptus grandis.

Despite the importance of Eucalyptus spp. in the pulp and paper industry, functional genomic approaches have only recently been applied to understand wood formation in this genus. We attempted to establish a global view of gene expression in the juvenile cambial region of Eucalyptus grandis Hill ex Maiden. The expression profile was obtained from serial analysis of gene expression (SAGE) library data produced from 3- and 6-year-old trees. Fourteen-base expressed sequence tags (ESTs) were searched against public Eucalyptus ESTs and annotated with GenBank. Altogether 43,304 tags were generated producing 3066 unigenes with three or more copies each, 445 with a putative identity, 215 with unknown function and 2406 without an EST match. The expression profile of the juvenile cambial region revealed the presence of highly frequent transcripts related to general metabolism and energy metabolism, cellular processes, transport, structural components and information pathways. We made a quantitative analysis of a large number of genes involved in the biosynthesis of cellulose, pectin, hemicellulose and lignin. Our findings provide insight into the expression of functionally related genes involved in juvenile wood formation in young fast-growing E. grandis trees.

Proteomic analysis of the cambial region in juvenile Eucalyptus grandis at three ages.

Recent advances in genomics and proteomics have provided an excellent opportunity to understand complex biological processes such as wood formation at the gene and protein levels. The aim of this work was to describe the proteins participating in the processes involved in juvenile wood formation by isolating proteins from the cambial region of Eucalyptus grandis, at three ages of growth (6-month-old seedlings, 3- and 6-year-old trees), and also to identify proteins differentially expressed. Using a 2-D-LC-MS/MS strategy we identified a total of 240 proteins, with 54 corresponding spots being present in at least two ages. Overall, nine proteins classified into the functional categories of metabolism, cellular processes, and macromolecular metabolism showed significant changes in expression. Proteins were classified into seven main functional categories, with metabolism representing 35.2% of the total proteins identified. The comparison of the reference maps showed not only differences in the expression pattern of individual proteins at each age, but also among isoforms. The results described in this paper provide a dynamic view of the proteins involved in the formation of juvenile wood in E. grandis.

Comparison of the expression profiles of susceptible and resistant Eucalyptus grandis exposed to Puccinia psidii Winter using SAGE.

Eucalyptus grandis Hill ex Maiden and its hybrids are commonly planted by the Brazilian pulp and paper industry, but they are the most susceptible to the neotropical rust disease caused by Puccinia psidii Winter. In an initial attempt to understand the mechanisms of resistance, we constructed two contrasting Serial Analysis of Gene Expression (SAGE) libraries using susceptible and resistant individuals from a segregating half-sibling E. grandis population. Using the Z-test we identified tags differentially expressed between the libraries, preferentially 239 in the susceptible and 232 in the resistant type individuals. Using public (Expressed Sequence Tags) EST databases, 40 of the susceptible and 70 of the resistant tags matched ESTs and were annotated. By comparing the type of genes and their expression levels, distinct differences between the libraries were observed. Susceptible plants showed gene expression linked to leaf senescence, generalised stress responses and detoxification, and are apparently incapable of inducing a competent host defence response. On the other hand, resistant plants showed genes upregulated for cellular polarisation, cytoskeleton restructuring, vesicle transport, and cellulose and lignin biosynthesis. In the resistant individuals, evidence for systemic resistance, anti-oxidative responses and a hypersensitive response was also observed, although no R gene was identified.