Location: Crops Pathology and Genetics Research2020 Annual Report
Objective 1: Determine the impact of conditionally-induced high plant hormone ascisic acid (ABA) production on drought tolerance of ornamentals and the potential for use in management practices to mitigate drought damage. Objective 2: Identify the physiological, biochemical, genetic and molecular bases of drought tolerance using transgenic plants with over-produced plant hormone ABA under stress- and alcohol-inducible systems. Objective 3: Determine molecular processes and the potential to retard floral senescence and enhance vase life in ethylene-insensitive flower senescence using Four o'clock (Mirabilis jalapa) as a model.
Objective 1: Test the strategy of upregulating the key ABA biosynthesis gene, NCED, with a plant-derived stress-inducible promoter pRD29A (cloned from Arabidopsis); use a chemically-induced system (alcohol-inducible promoter, ALC) to up-regulate the expression of NCED in petunia. Objective 2: Biological materials established or collected from Objective 1 will be subjected to either physiological, or biochemical and molecular analysis. Objective 3: Use Four o'clock (Mirabilis jalapa) as a model system for studying the molecular regulation of ethylene insensitive flower senescence. Four o'clock tissues from leaves (young and senescing), stems, roots, whole flowers (no petals) and petals (four stages, before opening, just fully-opened, senescing and wilted) will be harvested.
This report is for a bridge project which began December 15, 2018, and continues research from project 2032-21000-022-00D, "Improvement of Postharvest Performance of Ornamentals Using Molecular Genetic Approaches", which terminated on December 14, 2018. This is the final report for this project as the scientist for this project was incorporated into a new in-house project, 2032-21220-008-00D effective March, 2020. In support of Objective 1, research continued on the impact of conditionally-induced plant hormone abscisic acid (ABA) production on drought tolerance of nursery plants and the potential for its use in management practices to mitigate drought damage. To improve drought resistance, ARS researchers in Davis, California, in collaboration with researchers at University of California, Davis, attempted to develop a simple and efficient genome editing technology using clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (CRISPR/CAS9) genome editing system. Experiments are in progress to generate expression constructs and transformants. In support of Objective 2, molecular responses to drought stress in a desert plant could suggest potential targets for genetically engineering drought-resistant horticultural crops. Resurrection plants, such as Myrothamnus (M.) flabellifolia, are capable of withstanding extreme dehydration. However, the mechanisms by which they survive and revive after drought are not well understood. ARS scientists in Davis, California, in collaboration with researchers at Sichuan Agricultural University, China, characterized transcription factors that were isolated from M. flabellifolia. These genes would control other genes ability to switch-on and were transformed into the model plant Arabidopsis for characterization of their potential functions relating to drought resistance. Transgenic Arabidopsis plants with over-expression of these genes maintained higher water content and exhibited better water-use efficiency than non-transformed control plants. These regulatory genes control a range of genes with protective effects on drought stress in plant. In support of Objective 3, flower senescence and fruit ripening may show similar regulatory mechanism, are under tight genetic control and involve changes in gene expression. Genetic regulatory mechanisms that govern the natural aging process (senescence/ripening) is not well understood. To identify key genes and pathways that control senescence/ripening, ARS scientists in Davis, California, in collaboration with researchers at China Agricultural University China and Chongqing University China, conducted characterizations of transcription factors in rose and tomato. Over-expression and down-regulation of these transcription factors significantly changed cell death process. These results indicate that these regulatory genes function as positive regulators in controlling aging and ripening processes and suggest that manipulation of these genes may provide a useful tool for extending shelf life of flowers and fruits.
Zhao, X., Yuan, X., Chen, S., Fu, D., Jiang, C. 2019. Metabolomic and transcriptomic analyses reveal that a MADS-box transcription factor TDR4 regulates tomato fruit quality. Frontiers in Plant Science. 10. https://doi.org/10.3389/fpls.2019.00792.
Gao, Y., Liu, Y., Liang, Y., Lu, J., Jiang, C., Fei, Z., Jiang, C., Ma, C., Gao, J. 2019. Rosa hybrid RhERF1 and RhERF4 mediate ethylene and auxin-regulated petal abscission by influencing pectin degradation. Plant Journal. 99(6):1159-1171. https://doi.org/10.1111/tpj.14412.
Yuan, Y., Xu, X., Gong, Z., Tang, Y., Wu, M., Yan, F., Zhang, X., Zhang, Q., Yang, F., Hu, X., Yang, Q., Luo, Y., Mei, L., Zhang, W., Jiang, C., Lu, W., Li, Z., Deng, W. 2019. Auxin response factor 6A regulates photosynthesis, sugar accumulation, and fruit development in tomato. Horticulture Research. 6. https://doi.org/10.1038/s41438-019-0167-x.
Celikel, F.G., Reid, M.S., Jiang, C. 2020. Postharvest physiology of cut Gardenia jasminoides flowers. Scientia Horticulturae. 261. https://doi.org/10.1016/j.scienta.2019.108983.