An investigation of the effects of two important post-transcriptional regulatory mechanisms, gene transcription and alternative splicing (AS), on the wood formation of Eucalyptusurophylla × tereticornis, an economic tree species widely planted in southern China, was carried out. We performed RNA-seq on E. urophylla × tereticornis hybrids with highly contrasting wood basic density (BD), cellulose content (CC), hemicellulose content (HC), and lignin content (LC). Signals of strong differentially expressed genes (DEGs) and differentially spliced genes (DSGs) were detected in all four groups of wood properties, suggesting that gene transcription and selective splicing may have important regulatory roles in wood properties. We found that there was little overlap between DEGs and DSGs in groups of the same trait. Furthermore, the key DEGs and DSGs that were detected simultaneously in the four groups tended to be enriched in different Gene Ontology terms, Kyoto Encyclopedia of Genes and Genomes pathways, and transcription factors. These results implied that regulation of gene transcription and AS is controlled by independent regulatory systems in wood formation. Lastly, we detected transcript levels of known wood biosynthetic genes and found that 79 genes encoding mainly enzymes or proteins such as UGT, LAC, CAD, and CESA may be involved in the positive or negative regulation of wood properties. This study reveals potential molecular mechanisms that may regulate wood formation and will contribute to the genetic improvement of Eucalyptus.

Archidendron clypearia (Jack) I. C. Nielsen is an important tree species for traditional medicine purposes such as anti-inflammatory, detoxification, uric acid control and neuro-protection. Here, a set of 15 microsatellite markers were used to fingerprint 248 elite genotypes from six origins of A. clypearia and investigate the genetic structure of these genotypes. A total of 170 alleles were amplified. The elite genotypes showed moderate genetic variability, with mean observed heterozygosity (H_o) and expected heterozygosity (H_e) being 0.651 and 0.699, respectively. Each of the elite genotypes could be fingerprinted uniquely. The cumulative probability of identity (PI) and the cumulative probability of paternity exclusion (PE) were 2.25 × 10⁻¹² and 0.999992, respectively, demonstrating the extremely high power of the markers for genotype identification. In STRUCTURE and clustering analyses, the same origin of elite genotypes tended to be grouped in a sub-population and clustered closely, but some genotypes from different geographic origins were mixed, suggesting a low level of genetic differentiation between the origins. These results can contribute to the protection and management of the elite genotype resources of A. clypearia and the comprehensive understanding of its genetic structure.