Eucommia ulmoides has attracted much attention as a valuable natural rubber (Eu-rubber) production tree. As a strategic material, Eu-rubber plays a vital role in general and defence industries. However, the study of Eu-rubber biosynthesis at a molecular level is scarce, and the regulatory network between microRNAs (miRNAs) and messenger RNAs (mRNAs) in Eu-rubber biosynthesis has not been assessed. In this study, we comprehensively analyzed the transcriptomes, small RNAs (sRNAs) and degradome to reveal the regulatory network of Eu-rubber biosynthesis in E. ulmoides. A total of 82,065 unigenes and 221 miRNAs were identified using high-throughput sequencing; 20,815 targets were predicted using psRNATarget software. Of these targets, 779 miRNA-target pairs were identified via degradome sequencing. Thirty-one miRNAs were differentially expressed; 22 targets of 34 miRNAs were annotated in the terpenoid backbone biosynthesis pathway (ko00900) based on the Kyoto Encyclopedia of Genes and Genomes (KEGG). These miRNAs were putatively related to Eu-rubber biosynthesis. A regulatory network was constructed according to the expression profiles of miRNAs and their targets. These results provide a comprehensive analysis of transcriptomics, sRNAs and degradome to reveal the Eu-rubber accumulation, and provide new insights into genetic engineering techniques which may improve the content of Eu-rubber in E. ulmoides.

The taxonomy of an ancient gymnosperm genus Taxus, with high value in horticulture and medicine, is perplexing because of few reliable morphological characters for diagnosing species. Here, we performed a comprehensive investigation of the evolutionary dynamics of Taxus chloroplast genomes and estimated phylogenetic relationships, divergence times, and ancestral distributions of Taxus species by comparing 18 complete chloroplast genomes. The variations across the chloroplast genome of different Taxus species indicated that remarkably varied genome variations across lineages have reshaped the genome architecture. Our well-resolved phylogeny supported that T. brevifolia Nutt. was basal lineages followed by the other North America lineages. Divergence time estimation and ancestral range reconstruction suggested that the Taxus species originated in North America in the Late Cretaceous and revealed that extant Taxus species shared a common ancestor whose ancestral distribution area was probably in North America and afterwards the earliest members expanded to Southeast Asia from where Chinese Taxus species originated. The predominant European species have more closer relationship with the Eastern Asian species and the speciation of Eurasia species arose from several dispersal and vicariance events in the Miocene. Genome-wide scanning revealed 18 positively selected genes that were involved in translation and photosynthesis system in Taxus, which might be related to the adaptive evolution of Taxus species. The availability of these complete chloroplast genomes not only enhances our understanding of the elusive phylogenetic relationships and chloroplast genome evolution such as conservation, diversity, and gene selection within Taxus genus but also provides excellent templates and genetic bases for further exploration of evolution of related lineages as well as for plant breeding and improvement.

Unsaturated fatty acids (UFA) in lipids are the key to nutraceutical oil applications, with various potential applications in nutraceutical functional foods and pharmaceutical industries. In Idesia polycarpa (Salicaceae), more than 80 % of UFA have been found in the fruits; yet, the underlying genetic mechanism remains poorly understood. Due to the lack of theoretical research on the genes related to lipid biosynthesis and the complete genetic transformation system of I. polycarpa fruit, the selection and breeding of I. polycarpa, an excellent oil tree, has been severely restricted. In-depth understanding of the molecular mechanism and gene function of lipid biosynthesis of I. polycarpa fruit is therefore of great significance for the development of I. polycarpa resources. This is not only conducive to the genetic improvement of I. polycarpa by molecular breeding technologies but can also provide a reference for the study of the gene functions of other oil plants. In this study, the FA accumulation patterns of I. polycarpa fruits during 8 growth periods were analysed. Fruit from two developmental periods with different UFA levels were analysed for RNA sequencing by an Illumina NovaSeq 6000 HiSeq platform. De novo transcriptome assembly presented 115,350 unigenes and 4382 differentially expressed genes (DEGs). Functional annotation in the KEGG pathway and combined with DEG data revealed candidate genes potentially involved in UFA biosynthesis. Expression analysis of q-PCR of IpDGAT2, IpGPAT, IpKASII, IpSAD, IpFAD2, IpFAD3 and IpFAD8 suggested that these genes are highly involved in UFA biosynthesis. Full-length candidate genes were cloned and analysed by bioinformatic tools, and function analysis of IpSAD and IpFAD3 showed that these genes regulated the products of linoleic acid metabolism. This study provides a foundation for UFA biosynthesis in Idesia polycarpa, facilitating its genetic breeding in the future.

The multi-factorial hypothesis of quantitative trait inheritance originated from Nilson’s wheat hybridization experiments. It takes unit traits as the object and is based on the binomial distribution mathematically. Due to the requirement of the same distribution, it cannot include genes of other distributions. This is its limitation. Moreover, it does not incorporate the environmental effects that constitute the phenotype, so it is not comprehensive enough. This article started from the overallness of quantitative traits, was based on the central limit theorem, and was analyzed from both the genotype and the environment and proposed the assumption on the inheritance of dual multi-factors and tri-normal distributions of quantitative traits. This genetic model was tested with practical examples, and three inferences were made. Method and Results: Firstly, the overallness of quantitative traits was discussed, thus the above assumption was proposed. Next, using many examples of normal distribution of quantitative characters in the homogeneous populations, the research on the identification of the environments without GEI was carried out. Then, the examples of normal distribution of the same quantitative characters in the homogeneous populations and in the segregated populations of the same family were used. By means of normal distribution of quantitative characters in the homogeneous populations, it was indicated that the test locations were the environments without GEI. By utilizing the properties of normal distribution and variance, it was proven that normal distribution of phenotypic value for quantitative traits in a segregated population was formed by adding normal distribution of genotypic value and environmental effect, which enables the genetic model to be tested in practice. Three types of normal distribution of quantitative traits were inferred, indicating that the quantitative characters of a considerable number of organisms in nature obey a normal distribution, expressing continuous variation.