Abstract
Eucalyptus grandis is a commercially important hardwood species and is known to be susceptible to a number of pests and pathogens. Determining mechanisms of defense is therefore a research priority. The published genome for E. grandis has aided the identification of one important class of resistance (R) genes that incorporate nucleotide binding sites and leucine-rich repeat domains (NBS-LRR). Using an iterative search process we identified NBS-LRR gene models within the E. grandis genome. We characterized the gene models and identified their genomic arrangement. The gene expression patterns were examined in E. grandis clones, challenged with a fungal pathogen (Chrysoporthe austroafricana) and insect pest (Leptocybe invasa). One thousand two hundred and fifteen putative NBS-LRR coding sequences were located which aligned into two large classes, Toll or interleukin-1 receptor (TIR) and coiled-coil (CC) based on NB-ARC domains. NBS-LRR gene-rich regions were identified with 76% organized in clusters of three or more genes. A further 272 putative incomplete resistance genes were also identified. We determined that E. grandis has a higher ratio of TIR to CC classed genes compared to other woody plant species as well as a smaller percentage of single NBS-LRR genes. Transcriptome profiles indicated expression hotspots, within physical clusters, including expression of many incomplete genes. The clustering of putative NBS-LRR genes correlates with differential expression responses in resistant and susceptible plants indicating functional relevance for the physical arrangement of this gene family. This analysis of the repertoire and expression of E. grandis putative NBS-LRR genes provides an important resource for the identification of novel and functional R-genes; a key objective for strategies to enhance resilience.
Highlights
Our scrutiny of the E. grandis genome for putative NBSLRR genes has identified an extensive gene family with some differences to other woody plant species
Retention of nucleotide binding sites and leucine-rich repeat domains (NBS-leucine rich repeat domain (LRR)) genes in clusters and superclusters is an important feature for all plants, E. grandis maintains a smaller percentage of single genes compared to P. trichocarpa and A. thaliana
We found that a large proportion of putative nucleotidebinding site (NBS)-LRR genes are expressed, including 423 complete gene models, and are transcriptionally active
Summary
NBS-LRR Genes in Eucalyptus grandis stress is an urgent research priority with the goal of developing resilient forestry. As an important commercial species, E. grandis was selected as one of the first woody plants for genome sequencing (Myburg et al, 2011). The annotated draft genome for E. grandis, from a 17 year old inbred clone, BRASUZ1 (genome size of 640 Mbp, 11 haploid chromosomes), was released in 2011 with more comprehensive annotation data published in 2014 (Myburg et al, 2014). The availability of genomic sequence data for E. grandis makes it a useful model plant for the study of defense responses to current and emerging pathogens across a range of species within the Myrtaceae family
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
