Location: Grape Genetics Research Unit (GGRU)
Project Number: 8060-21220-007-021-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2021
End Date: Aug 31, 2023
The objective of this cooperative project is to develop and use novel gene editing tools for improving flowering traits of horticultural and floricultural plants. Initially we will focus on modifying genes for producing genetically modified grapevines and tree peony (Paeonia suffruticosa Andrews) with low chilling requirement and continuous flowering. Grapes are one of the important fruit crops with significant economic and nutritional value. They are perennial species and require various threshold levels of chilling hours before flowering. Researchers have long been exploring ways of modifying flowering time of grapes for various breeding and research purposes such as developing early or late flowering cultivars and accelerating sexual generations in crosses. Tree peony is an important woody ornamental plant known for its large and colorful flowers. Tree peonies requires 500 - 1,000 chilling hours to break endodormancy for flowering. Short and uniform bloom time are major undesirable traits for tree peony to be used as a year-around ornamental plant. Conventional breeding approaches to improving these traits are time-consuming, labor-intensive and very challenging due to the lack of desirable germplasm resources. Recent studies on plant flowering pathway genes have revealed that manipulating expression of major flowering pathway genes [e.g. FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), TERMINAL FLOWER1/2 (TFL1/2)], SHORT VEGETATIVE PHASE (SVP), or DORMANCY ASSOCIATED MADS-BOX (DAM) genes can be a powerful approach to promoting flowering, enabling continuous flowering, and reducing chilling requirement in plants. In this study, we will develop and use novel tissue culture, transformation and genome editing technologies for modifying flowering genes to develop genetically modified grapevines and tree peonies with low-chilling requirements and continuous flowering. The tools and knowledge generated from the study will be applied to other horticultural and floricultural plants.
The project will be pursued in two phases. In the first phase, we will focus on development of an efficient tissue culture, transformation and regeneration system through either organogenesis or somatic embryogenesis. In parallel, we will clone and evaluate TERMINAL FLOWER1 (TFL1) or TFL2 and SVPs from grapevines and tree peony. Once the tissue culture, transformation and regeneration systems are established and TFL1/TFL2 and SVPs flowering gene are identified and characterized, the project will move to its second phase to knock out TERMINAL FLOWER1 TFL1/TFL2 or SVPs through CRISPR-Cas9 editing to create continuous flowering phenotypes. If modification of neither TFL1/TFL2 nor SVPs produces a desirable phenotype, we will examine the feasibility of generating a continuous flowering trait in tree peony through overexpression of FLOWERING LOCUS T (FT) and/or SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1).