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Huaren apricot and almond are two tree species with nuts as the main economically important products. Crossbreeding these two species might be a good approach for combining the traits of large seed kernel of almond with the wide adaptability of Huaren apricot. However, the molecular mechanism of hybridization incompatibility between Huaren apricot and almond has remained unclear until date. In the present study the transcriptomes of developing fruits after interspecific hybridization between Huaren apricot and almond and after intraspecific hybridization of Huaren apricot were compared to elucidate the possible molecular mechanisms of fruit development at the gene expression level. Approximately 562,535,240 clean reads were assembled, and 25,692 unigenes were identified. Totally, 270 differentially expressed genes (DEGs) were identified, of which 221 were up-regulated and 49 were down-regulated in almond as compared with Huaren apricot. Functional annotation analysis indicated that the expression of cinnamyl alcohol dehydrogenase and EREBP were significantly up-regulated, whereas GA2ox and MADS were down-regulated in the intraspecific hybridization (PN) as compared with the interspecific hybridization (MN). Moreover, these genes might play an important role in fruit development. This study provides novel insights into the molecular mechanisms of fruit development in interspecific and intraspecific hybrids.

The 2′,3′-cycling ribonuclease (RNase) genes are catalysts of RNA cleavage and include the RNase T2 gene family. RNase T2 genes perform important roles in plants and have been conserved in the genome of eukaryotic organisms. In this study we identified 21 EURNS genes in Eucommia ulmoides Oliver (E. ulmoides) and analyzed their structure, chromosomal location, phylogenetic tree, gene duplication, stress-related cis-elements, and expression patterns in different tissues. The length of 21 predicted EURNS proteins ranged from 143 to 374 amino acids (aa), their molecular weight (MW) ranged from 16.21 to 42.38 kDa, and their isoelectric point (PI) value ranged from 5.08 to 9.09. Two classifications (class I and class III) were obtained from the conserved domains analysis and phylogenetic tree. EURNS proteins contained a total of 15 motifs. Motif 1, motif 2, motif 3, and motif 7 were distributed in multiple sequences and were similar to the conserved domain of RNase T2. EURNS genes with similar structure and the predicted EURNS proteins with conserved motif compositions are in the same group in the phylogenetic tree. The results of RT-PCR and transcription data showed that EURNS genes have tissue-specific expression and exhibited obvious trends in different developmental stages. Gene duplication analysis results indicated that segment duplication may be the dominant duplication mode in this gene family. This study provides a theoretical basis for research on the RNase T2 gene family and lays a foundation for the further study of EURNS genes.

Eucommia ulmoides Oliver. (E. ulmoides) is an important medicinal and economic tree species, and “Huazhong No.12” (HZ12) is the only existing red leaf genotype of E. ulmoides. In this study, phenotype/anatomic observation and photosynthetic pigment content detection were performed on “Huazhong No.11” (HZ11, green leaf E. ulmoides) and HZ12. Additionally, the transcriptome sequencing data of HZ11 and HZ12 leaves were also analyzed and compared. The results showed that the palisade tissue of HZ12 leaf was red, while the palisade tissue of HZ11 leaf was green. Chlorophyll a, b, a+b, and carotenoid contents of HZ12 leaf were significantly lower than that of HZ11 leaf. While the total flavonoids and anthocyanin contents in HZ12 leaf were significantly higher than that in HZ11 leaf. Transcriptome analysis indicated that, compared with HZ12, there were 26 MYB and 49 bHLH TF genes, and some structural genes were differentially expressed in HZ11, and among these differentially expressed genes (DEGs), 2 MYB, 1 bHLH, 1 F3′H, 1 F3′5′H, 5 DFR and 9 GT genes were involved with flavonoid biosynthesis and anthocyanin biosynthesis pathways. Taken together, the results that achieved in the present study not only provide valuable clues for the excavation on anthocyanin biosynthesis related genes and the corresponding gene regulation networks in E. ulmoides, but also provide reference for the leaf coloration mechanism research in other woody plant species.

Eucommia ulmoides, also called hardy rubber tree, is an economically important tree; however, the lack of its genome sequence restricts the fundamental biological research and applied studies of this plant species. Here, we present a high-quality assembly of its ∼1.2-Gb genome (scaffold N50 = 1.88 Mb) with at least 26 723 predicted genes for E. ulmoides, the first sequenced genome of the order Garryales, which was obtained using an integrated strategy combining Illumina sequencing, PacBio sequencing, and BioNano mapping. As a sister taxon to lamiids and campanulids, E. ulmoides underwent an ancient genome triplication shared by core eudicots but no further whole-genome duplication in the last ∼125 million years. E. ulmoides exhibits high expression levels and/or gene number expansion for multiple genes involved in stress responses and the biosynthesis of secondary metabolites, which may account for its considerable environmental adaptability. In contrast to the rubber tree (Hevea brasiliensis), which produces cis-polyisoprene, E. ulmoides has evolved to synthesize long-chain trans-polyisoprene via farnesyl diphosphate synthases (FPSs). Moreover, FPS and rubber elongation factor/small rubber particle protein gene families were expanded independently from the H. brasiliensis lineage. These results provide new insights into the biology of E. ulmoides and the origin of polyisoprene biosynthesis.

Eucommia ulmoides Oliver produces trans-1,4-polyisoprene (TPI or Eucommia rubber), with leaves and bark as the main sources. Raw materials from short rotation coppice (SRC) cultures for TPI industrialization are a valuable option. Currently, there is a shortage of field yield data beginning from early establishment of Eucommia SRC to support TPI manufacturers. We investigated an Eucommia SRC plantation established in 2015 with application of four plant growth regulators in Mengzhou Forest Farm, China, during its first two annual rotations. By using an orthogonal experimental design, productivity related data were derived after each growing season. We observed significant variations in biomass yield and TPI productivity among the 12 dosages of 4 regulator types and control, with plants treated with brassinolide at 5 mg L−1, DCPTA at 500 mg L−1 and DTA-6 at 20 mg L−1 reaching the highest TPI productivity among treatments of 406 kg ha−1, 391 kg ha−1 and 382 kg ha−1 in the second rotation, respectively, all of which were more than 1.4 times that of the control. Foliage spray of regulators led to more and larger leaves, more bark yield, higher tree height, and higher leaf TPI content, which reflected the enhancing effects of regulators on leaf and bark biomass as well as TPI productivities in both the first and second rotations. Meanwhile, the harvest of Eucommia leaf and bark from the coppice plantation was less labor intensive than that from tall mature trees. Our study suggested that the annual rotation period and increase of TPI from Eucommia SRC by application of regulators could reduce the payback period. Therefore, we recommend the application of growth regulators to coppice Eucommia plantations beginning from the first rotation as an economic means to increase TPI production.

The WRINKLED1 (WRI1) gene is a well-established key transcriptional regulator involved in the regulation of fatty acid biosynthesis in developing seeds. In this study, a new WRI1 gene was isolated from seeds of Eucommia ulmoides and named EuWRI1. A close link between gibberellins signaling and EuWRI1 gene expression was suggested in this study. Functional characterization of EuWRI1 was elucidated through seed-specific expression in tobacco. In transgenic tobacco, the expression of EuWRI1 in eight independent transgenic lines was detected by semiquantitative RT-PCR. The relative mRNA accumulation of genes encoding enzymes involved in fatty acid biosynthesis (biotin carboxyl carrier protein and keto-ACP synthase 1) was also assayed in tobacco seeds. Analysis of the seeds oil content and starch content indicated that the transgenic lines showed a significant increase in seeds oil content, whereas starch content decreased significantly. Further analysis of the fatty acid composition revealed that palmitic acid (16:0), linoleic acid (18:2) and linolenic acid (18:3) increased significantly in seeds of transgenic tobacco lines, but stearic acid (18:0) levels significantly declined. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:337-346, 2018.

Eucommia ulmoides (E. ulmoides) is a significant national strategic resource in China. It is a natural high quality rubber resource, with great development potential. We found large differences in rooting ability during adventitious root (AR) formation in two E. ulmoides improved varieties. Therefore, we used two improved varieties of E. ulmoides, ‘Huazhong 6’ (H6, with rooting rate 85.3%) and ‘Huazhong 8’ (H8, with rooting rate 22.5%) to explore the cutting rooting mechanism. In this study, we mainly determined the morphological development process of E. ulmoides cutting rooting, and compared the rooting-related indexes of the two improved varieties, and the changes in physiological indexes closely related to rooting, which include endogenous hormones, oxidases and nutrients in the phloem of the basal stem. The results showed that indole–3–acetic acid (IAA), zeatin riboside (ZR), IAA/ZR and indoleacetic acid oxidase (IAAO) were the key factors that caused big differences in rooting ability between the two E. ulmoides improved varieties. The increase in endogenous hormone IAA content and IAA/ZR value were necessary for the formation of AR. The increase in IAA content was beneficial to AR formation. The activity of IAAO was significantly negatively correlated with the rooting ability of the E. ulmoides cuttings. The high IAAO activity of the H8 cuttings led to the consumption of IAA. Although the content of IAA increased, the rooting conditions were not reached. The accumulation of nutrients before rooting also has an important effect on rooting, it is easy for cuttings to root when the carbon–nitrogen ratio (C/N) value is high. This research provides an improved understanding of the cellular and physiological underpinnings of the AR process in woody plants. In addition, it provides a theoretical basis and foundation for subsequent research on E. ulmoides cuttage technology.