Research Project: Improvement of Postharvest Performance of Ornamentals Using Molecular Genetic Approaches

Location: Crops Pathology and Genetics Research

2019 Annual Report

Objectives
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.

Approach
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.

Progress Report
This report is for a new 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. In support of Objective 1, research continued on the impact of conditionally-induced plant hormone abscisic acid (ABA) production on drought tolerance of ornamentals and the potential for its use in management practices to mitigate drought damage. Using molecular genetic approaches to improve drought resistance in ornamentals, ARS researchers in Davis, California, in collaboration with researchers at University of California, Davis, attempted to develop a simple and efficient genome editing technology. Preliminary results suggest that a gene encoding for phytoene desaturase (PDS), an essential plant carotenoid biosynthetic enzyme, could be edited using clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9 (CRISPR/CAS9) genome editing technology. In support of Objective 2, global climate change may result in a frequent occurrence of extreme rainfall events in some regions, which may increase the demand for improvement of plant tolerance to waterlogging. ARS researchers in Davis, California, identified a transcription factor, namely ethylene-responsive element binding factor (PhERF) that is involved in the regulation of various stress responses in plants. To study the regulatory role of PhERF2 in waterlogging responses, transgenic petunia plants with reduced expression and overexpression of PhERF2 were generated. Compared with wildtype plants, PhERF2-down regulation compromised the tolerance of petunia seedlings to waterlogging, while overexpression of PhERF2 improved the survival of seedlings subjected to waterlogging. The results demonstrate that PhERF2 contributes to petunia waterlogging tolerance through modulation of programmed cell death (PCD) and alcoholic fermentation system.

Accomplishments
1. Improvement of waterlogging tolerance in potted plants. Global climate change may result in a frequent occurrence of extreme rainfall events in some regions, which may increase the demand for improvement of plant tolerance to waterlogging. ARS researchers in Davis, California, identified a transcription factor, namely ethylene-responsive element binding factor (PhERF) that is involved in regulation of various stress responses in plants. Transgenic petunia plants with overexpression of PhERF2 improved the survival of seedlings subjected to waterlogging compared to wildtype control plants. This approach provides an excellent means for improving waterlogging tolerance for a wide variety of agricultural crops.

Review Publications
Gao, Y., Wei, W., Zhao, X., Tan, X., Fan, Z., Zhang, Y., Jing, Y., Meng, L., Zhu, B., Zhu, H., Chen, J., Jiang, C., Grierson, D., Luo, Y., Fu, D. 2018. A NAC transcription factor, NOR-like1, is a new positive regulator of tomato fruit ripening. Horticulture Research. 5:75. https://doi.org/10.1038/s41438-018-0111-5.
Yin, D., Sun, D., Norris, A.M., Han, Z., Ni, D., Jiang, C. 2019. PhERF2, an ethylene-responsive element binding factor, plays an essential role in waterlogging tolerance of petunia. Horticulture Research. 6:83. https://doi.org/10.1038/s41438-019-0165-z.
Zhang, S., Feng, M., Chen, W., Zhou, X., Lu, J., Wang, Y., Li, Y., Jiang, C., Gan, S., Ma, N., Gao, J. 2019. In rose, transcription factor PTM balances growth and drought survival via PIP2;1 aquaporin. Nature Plants. 5:290-299. https://doi.org/10.1038/s41477-019-0376-1.
Gao, Y., Zhu, N., Zhu, X., Wu, M., Jiang, C., Grierson, D., Luo, Y., Shen, W., Zhong, S., Fu, D., Qu, G. 2019. Diversity and redundancy of the ripening regulatory networks revealed by the fruitENCODE and the new CRISPR/Cas9 CNR and NOR mutants. Horticulture Research. 6:39. https://doi.org/10.1038/s41438-019-0122-x.
Ma, Y., Ban, Q., Shi, J., Dong, T., Jiang, C., Wang, Q. 2018. 1-Methylcyclopropene (1-MCP), storage time, and shelf life and temperature affect phenolic compounds and antioxidant activity of ‘Jonagold’ apple. Postharvest Biology and Technology. 150:71-79. https://doi.org/10.1016/j.postharvbio.2018.12.015.
Zhu, T., Wang, L., You, F.M., Rodriguez, J., Deal, K., Chen, L., Li, J., Chakraborty, S., Balan, B., Jiang, C., Browne, P.J., Leslie, C., Aradhya, M.K., Dandekar, A., McGuire, P.E., Kluepfel, D.A., Dvorak, J., Ming-Chen, L. 2019. Sequencing a Juglans regia × J. microcarpa hybrid yields high-quality genome assemblies of parental species. Horticulture Research. 6:55. https://doi.org/10.1038/s41438-019-0139-1.
Margenot, A., Rippner, D., Dumlao, M., Nezami, S., Green, P.G., Parikh, S., McElrone, A.J. 2018. Copper oxide nanoparticle effects on root growth and hydraulic conductivity of two vegetable crops. Plant and Soil. 431(1-2):333-345. https://doi.org/10.1007/s11104-018-3741-3.