2007 Annual Report
1a.Objectives (from AD-416)
1. Determine flower freshness during postharvest handling.
2. Development of a freshness index.
3. Identification and characterization of senescence-associated genes/promoters: a) Isolation of gene specific promoters; b) Targeted regulation of senescence-associated genes; c) Targeted inihibition of protein synthesis.
1b.Approach (from AD-416)
1) Freshly cut flowers of different species (at least two cultivars for each species) will held at different temperatures, and their respiration rate will be determined.
2) From a pre-existing database of genes whose expression changes during petal senscence in daylily, four o'clocks, and daffodils, as well as published databases on iris, carnation, and petunia we will identify genes whose expression pattern suggests an association with senescence.
3a) Using EST collections we will identify genes whose expression changes dramatically in the early stages of floral senescence.
3b) Transgenic petunia plants will be generated using standard techniques, and the life of the flowers from the transformed plants will be compared with that of control plants.
3c) Transform petunia with constructs combining floral senesence-specific promoters with genes encoding proteins known to interfere with ribosome function. Documents SCA with UC Davis.
This report documents research conducted under a specific cooperative agreement between ARS & UC Davis. Additional details can be found in the report of the parent CRIS 5306-13210-001-00D,Sustainable Floriculture Productions. This project focuses on improving the postharvest handling & performance of floral crops. The over-riding need of the cut flower industry is to increase the consumption of flowers in the U.S. Increasing consumption would dramatically alter the balance between supply & demand, resulting in higher returns to all segments of the industry. The key to increasing consumption is improving the vase life of cut flowers. We have continued our efforts to develop tools for predicting residual vase life & basic studies with the long-term goal of breeding longer-lasting flowers.1)Develop tools to improve temperature management in the postharvest chain-We are working with a company in CA, to conduct pilot trials on the use of active RFID tags to monitor temperatures during the transportation of cut flowers. Initial tests with a wholesaler were promising. We demonstrated the effectiveness of RFID for reporting the effect of temperature abuse during transportation on potential vase life of flowers.2)Develop simple tools for testing flower freshness-We are mining public gene databases to identify promising candidate genes for use as'freshness'indicators. We are using a very elegant model system, Nicotiana mutabilis, which changes color as it ages. The genes regulating this color change are likely targets for our freshness indicator.3)Investigate means of reducing Botrytis infection-We have tested two novel chemicals from Syngenta as potential pre- & post-harvest fungicides for controlling the infection. We have also shown that most of the infection occurs AFTER the flowers have been harvested, which emphasizes the importance of careful handling & proper temperature management.4)Longer lasting flowers through silencing protein synthesis-We already know that chemical inhibitors that interfere with the machinery required for gene transcription & protein synthesis can greatly extend the life of short-lived flowers. We aim to isolate the flower-specific promoter, & produce transgenic plants where the promoter is used to drive an antisense of a gene that is critical for protein synthesis to turn off protein synthesis and to delay petal senescence. We have now isolated the promoter of a gene from Mirabilis jalapa, which shows strong up-regulation during flower senescence. We have shown that it is recognized in species as diverse as petunias & carnations. Our data suggest that this promoter is quite specific to senescing flower petals. We have isolated two petunia homologs of proteins that are part of the ribosomes & important in protein synthesis. We have silenced these genes in the leaves of tobacco plant using Virus-Induced Gene Silencing(VIGS). Where the silencing has occurred in the tobacco & petunia leaves, the cells have stopped growing. Non-silenced parts of the leaf continue to grow, resulting in the appearance of 'blisters'on the leaf. We are in the course of transforming petunia plants with a selected promoter/anitsense gene construct.
#3-Progress Report (continued)
The ADODR for this Specific Cooperative Agreement is actively involved with the cooperator and monitors the progress of the research by maintaining a complete file of the agreement and meeting with the cooperator during the timeframe of the SCA to discuss the specifics of the project and to review the program goals.