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    Identification and Expression Analysis of YABBY Gene Family in Hevea brasiliensis
    ZHANG Hongtao, XIAO Xiaohu, YANG Jianghua, QIN Yunxia, LONG Xiangyu, YIN Hongyan, FANG Yongjun
    Chinese Journal of Tropical Crops    2022, 43 (11): 2188-2198.   DOI: 10.3969/j.issn.1000-2561.2022.11.002
    Abstract3210)   HTML14)    PDF(pc) (8413KB)(55)       Save

    YABBY genes family is a plant-specific transcription factor, which plays an important role in the development of plant leaves, floral organs and abiotic stress response, but it has not been reported in rubber tree so far. In this study, eleven HbYABBY genes were identified from the genome of Hevea brasiliensis, and the gene structure, promoter regulatory elements, chromosome location and collinearity, phylogeny and gene expression were analyzed. The results showed that the HbYABBY family genes were distributed on nine chromosomes. The length of the encoded protein was between 141 and 233 amino acids, and the molecular weight was ranged from 14.75 to 26.41kDa. The promoter regions contained response elements such as stress response, among which the number of light response elements was the largest. Gene transcriptional analysis showed that HbYABBY had significant tissue-specific expression profile, eight genes were only highly expressed in leaves and flowers but not in latex and roots. During the leaf development, except for HbCRC1, the expression of the other 9 HbYABBY were significantly down-regulated, which indicated that HbYABBY were deeply involved in the regulation of leaf development of rubber trees. Furthermore, both transcriptional and RT-qPCR experiments showed that HbYABBY genes were continuously down-regulated under high temperature treatment, indicating the regulatory roles in high temperature stress responses of rubber trees. In this paper, YABBY genes were firstly reported in H. brasiliensis, the physical and chemical characteristics, expressions and function of the genes were preliminarily studied, which would provide a solid foundation to investigate the functions and evolution of HbYABBY genes.

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    Molecular Simulation on Miscibility of NR/BR Blends
    YUAN Xiaoqin, CAO Xianchao, MA Yanbin, YU Rentong, ZHAO Yanfang, CHEN Yongping, LIAO Jianhe
    Chinese Journal of Tropical Crops    2022, 43 (11): 2215-2223.   DOI: 10.3969/j.issn.1000-2561.2022.11.005
    Abstract3197)   HTML5)    PDF(pc) (2627KB)(37)       Save

    Natural rubber (NR) is widely used in various fields for its excellent comprehensive properties, however its poor heat resistance and aging resistance have great influence on the service life of NR products. The blending of natural rubber and cis-butadiene rubber (BR) could not only improve the tensile strength, wear resistance and tear resistance of the product, but also improve the service life and cold resistance of the product, and the NR/BR blends are widely used in tire manufacturing. When NR and BR are blended, the miscibility between NR and BR has an important influence on the phase structure and properties of the blends. In this study, Material Studio software was used to build the models required for the simulation, and molecular dynamics (MD) and dissipative particle dynamics (DPD) simulation methods were performed to investigate the miscibility of NR/BR blends from the molecular and mesoscopic scales at room temperature. The MD simulation results showed that the minimum repeating units of NR and BR in the NR/BR blend models were both 20; Models of NR/BR blends with mass ratios of 10/90, 30/70, 50/50, 70/30, 90/10 were constructed by Material Studio, by calculating the interaction parameter χ of each NR/BR blends, it was found that the interaction parameters of NR-BR in NR/BR blends (χNR/BR) were always smaller than the critical interaction parameter χC; The radial distribution function between molecules of NR/BR blends with different mass ratios were analyzed, and it was found that the radial distribution function ginter (r) between NR and BR molecules were always higher than that between NR and NR, BR and BR molecules of the same species, which showed that the interaction between different species (NR-BR) in the blends is stronger than the interaction between the same species (NR-NR, BR-BR). In addition, DPD simulations results calculated from the NR/BR blends with different mass ratios showed that the domain size of the dispersed phase of the blends increased with the increase of the dispersed phase content while macroscopic phase separation had always not been detected. Furthermore, the samples of NR/BR blends were prepared, and the miscibility of each blending system was confirmed with the results of dynamic mechanical analysis (DMA). The simulation results show that when NR and BR are blended with different mass ratios at room temperature, they always show good compatibility, and the experimental results are consistent with the results of molecular simulation.For this reason, molecular simulation will be of significance to study and predict the miscibility of polymer blend, and it will provide much more reliable guidance for experiment.

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