Background Mallotus oblongifolius, an evergreen shrub endemic to Hainan Island, China, is important both medicinally and economically. Due to its special medicinal significance and the continuing rise of market demand, its populations in the wild have been subject to long-term illegal and unrestrained collection. Hence, an evaluation of genetic variability is essential for the conservation and genetic reserve development of this species. Methods Sequence-related amplified polymorphism (SRAP) and inter-simple sequence repeat (ISSR) markers were employed to assess the genetic diversity and genetic structure of 20 natural populations of M. oblongifolius growing in different eco-geographical regions of Hainan Island, China. Results We revealed a considerable genetic diversity (h = 0.336, I = 0.5057, SRAP markers; h = 0.3068, I = 0.4657, ISSR markers) and weak genetic differentiation (Gst = 0.2764 for SRAP, Gst = 0.2709 for ISSR) with the same gene flow (Nm = 1.3092 for SRAP, Nm = 1.346 for ISSR) among the M. oblongifolius populations. The Mantel Test showed that the distribution of genetic variation among populations could not be explained by the pronounced geographical distances (r = 0.01255, p = 0.5538). All results of the Unweighted Pair Group Method with Arithmetic Mean (UPGMA), Neighbor-joining (NJ), Principal Coordinate Analysis (PCoA) and Bayesian analyses supported a habitat-specific genetic clustering model for M. oblongifolius, indicating a local adaptive divergence for the studied populations. Discussion We suggested that the habitat fragmentation and specificity for M. oblongifolius populations weakened the natural gene flow and promoted an adaptation to special habitats, which was the main reason for local adaptive divergence among M. oblongifolius.

Background: Partridge tea (Mallotus oblongifolius) is used as an important beverage and medical plant in Hainan province of China. Although some information about the morphology, cytology, and genetics of partridge tea has been reported in the literature, knowledge about this plant is still very limited. The leaves are the most important part for every tea plant, with a major role in nutrition and other functions. The leaves of different cultivars of partridge tea are different in colors and functions. The molecular mechanism of color formation of partridge tea leaf is still unclear. We reveal the molecular mechanism of the color difference between purple-red and green partridge tea leaves through metabolome and transcriptome analysis.Results: We identified 665 compounds in the two partridge tea cultivars through metabolome analysis. Among these compounds, the content of 324 differed between the two cultivars. We also annotated 50 042 unigenes in the two cultivars by transcriptome analysis; 9665 unigenes were expressed differently between the two cultivars. Using an integrated analysis of the metabolome and transcriptome data, we found that the compounds and genes involved in anthocyanin biosynthesis were up-regulated in the purple-red leaves, compared with the green leaves. Conclusion: Our results showed that the anthocyanin biosynthesis pathway genes were up-regulated, which resulted in the upregulation of the anthocyanin, making the leaf color purple-red. Our study reveals the molecular mechanism of the color difference between purple-red and green partridge tea, and lays a foundation for the genetic breeding of partridge tea genetic and the utilization of its volatile components.

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The marked increase in plant genomic data has provided valuable resources for investigating the dynamic evolution of duplicate genes in polyploidy. Brassica napus is an ideal model species for investigating polyploid genome evolution. The present study comprehensively analyzed DNA and RNA variation of two representative B. napus inbredlines, Zhongshuang11 and Zhongyou821, and we investigated gene expression levels of An and Cn subgenomes in multiple tissues of the two lines. The distribution of transmitted single nucleotide polymorphisms (SNPs) was significantly different in two subgenomes of B. napus. Gene expression levels were significantly negatively correlated with number of variations in replication and transcription of the corresponding genes, but were positively correlated with the ratios of transmitted SNPs from DNA to RNA. We found a higher density of SNP variation in An than that in Cn during DNA replication and more SNPs were transmitted to RNA during transcription, which may contribute to An expression dominance. These activities resulted in asymmetrical gene expression in polyploid B. napus. The SNPs transmitted from DNA to RNA could be an important complement feature in comparative genomics, and they may play important roles in asymmetrical genome evolution in polyploidy.