Quercus acutissima Carruth. is a Chinese important energy plant with high ecological and economic values. While the species chloroplast genome has been reported, its mitochondrial genome (mitogenome) is still unexplored. Here, we assembled and annotated the Q. acutissima mitogenome, and we compared its characteristic differences with several closely related species. The Q. acutissima mitogenome’s main structure is branched with three distinguished contigs (linear molecule 1, circular molecule 2, and circular molecule 3) with 448,982 bp total length and 45.72% GC content. The mitogenome contained 51 genes, including 32 protein-coding, 16 tRNA and 3 rRNA genes. We examined codon usage, repeated sequences, genome recombination, chloroplast to mitochondrion DNA transformation, RNA editing, and synteny in the Q. acutissima mitogenome. Phylogenetic trees based on 29 species mitogenomes clarified the species classification. Our results provided comprehensive information of Q. acutissima mitogenome, and they are expected to provide valuable information for Fagaceae evolutionary biology and to promote the species germplasm utilization.

The Chinese chestnut, Castanea mollissima Blume, a nut-bearing tree native to China and North Korea, belongs to the Fagaceae family. As an important genetic resource, C. mollissima is vital in enhancing edible chestnut varieties and offers significant insights into the origin and evolution of chestnut species. While the chloroplast genome of C. mollissima has been sequenced, its mitochondrial genome (mitogenome) remains largely uncharted. In this study, we have characterized the C. mollissima mitogenome, assembling it utilizing reads from both BGI and Nanopore sequencing platforms, and conducted a comparative analysis with the mitochondrial genomes of closely related species. The mitogenome of C. mollissima manifests a polycyclic structure consisting of two circular molecules measuring 363,232 bp and 24,806 bp, respectively. This genome encompasses 35 unique protein-coding genes, 19 tRNA genes, and three rRNA genes. A total of 139 SSRs were identified throughout the entire C. mollissima mitogenome. Furthermore, the combined length of homologous fragments between the chloroplast and mitochondrial genomes was 5766 bp, constituting 1.49% of the mitogenome. We also predicted 484 RNA editing sites in C. mollissima, demonstrating C-to-U RNA editing. Phylogenetic analysis of related species' mitogenomes showed that C. mollissima was closely related to Lithocarpus litseifolius (Hance) Chun and Quercus acutissima Carruth. Interestingly, the mitogenome sequences of C. mollissima, L. litseifolius, Q. acutissima, Fagus sylvatica L., and Juglans mandshurica Maxim did not show conservation in their alignments, indicating frequent genome reorganization. This report marks the inaugural study of the C. mollissima mitogenome, serving as a benchmark genome for economically significant plants within the Castanea genus. Moreover, it supplies invaluable information that can guide future molecular breeding efforts and contribute to the broader understanding of chestnut genomics.

Background: Eucommia ulmoides ‘Oliver’ is an economically important tree species with highly medicinal and ecological values that is naturally distributed in China. E. ulmoides ‘Huazhong No. 12’ (H12) is the only red-leaf genotype of this species. In this study, the pigment contents of H12 and E. ulmoides ‘Huazhong No. 11’ (H11, green leaves) were determined. The differential metabolites in H12 and H11 were detected by UPLC-MS/MS, and the differentially expressed genes were screened by transcriptome. Then the key metabolites and corresponding gene regulation in anthocyanin related metabolic pathway were analyzed.Results: The chlorophyll a, chlorophyll b and carotenoid contents in H12 leaves were lower than H11, while the total anthocyanin content in H12 was 4.06 times higher than in H11. There were 96 up-regulated metabolites in H12, including anthocyanin, proanthocyanidins, flavonoid and flavonol. Among them, four differentially expressed anthocyanins were identified. A total of 8,368 differentially expressed genes were selected from transcriptome between H12 and H11. The flavone and flavonol biosynthesis pathway, anthocyanin pathway and photosynthetic pathway were analyzed. Finally, EuCHI, EuF3'H, EuF3'5'H, EuDFR and Eu3MaT1 were recommended as the key genes. The cyanidin, cyanidin 3-malonyl-glucoside and cyanidin 3, 5-glucoside were responsible for the H12 red leaves.Conclusion: This study revealed the metabolites and gene regulation of anthocyanin synthesis, and the potential function between the anthocyanin and photosynthetic gene expression in E. ulmoides red leaves. Notably, the results also provided a reference for the study of other plant leaf-coloring mechanisms.