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Title: EXPRESSION OF THE GRAPEVINE STILBENE SYNTHASE GENE VST1 IN PAPAYA PROVIDES INCREASED RESISTANCE AGAINST DISEASES CAUSED BY PHYTOPHTHORA PALMIVORA

Author
item ZHU, YUN - HI AG RES CNT
item AGBAYANI, RICELLE - HI AG RES CNT
item JACKSON, MEL - HI AG RES CNT
item TANG, C - U.H. HAWAII
item Moore, Paul

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2004
Publication Date: 11/25/2004
Citation: Zhu, Y.J., Agbayani, R., Jackson, M.C., Tang, C.S., Moore, P.H. 2004. Expression of the grapevine stilbene synthase gene vst1 in papaya provides increased resistance against diseases caused by phytophthora palmivora. Planta 220:241-250.

Interpretive Summary: Phytophthora species include several plant pathogens responsible for crown rots or collar rots of many woody and herbaceous plants world-wide. They are especially important diseases on fruit and nut crops such as citrus, avocado, stone fruits, walnut, apple, peppers, soybean, and papaya. Resistant germplasm for use as rootstocks and breeding to develop cultivars is available in some crops but not others. Transgenic approaches may be viable when resistance is lacking in otherwise acceptable cultivars as was the case with Hawaii's transgenic papaya cultivar 'Rainbow.' We transformed Rainbow with a resistance gene from grapevine to produce new lines that show good resistance in greenhouse trials. These lines will be advanced to field trials for performance in fruit production for resistance to Phytophthora. This success adds to the number of species that can be improved by expression of a transgene encoding stilbene synthase. The papaya lines developed may prove beneficial to the papaya fruit industry.

Technical Abstract: The phytoalexin resveratrol (trans-3,5,4'-trihydroxy-stilbene), a natural component of resistance to fungal diseases in many plants, is synthesized by the enzyme trihydroxystilbene synthase (stilbene synthase, EC 2.3.1.95) which appears to be deficient or lacking among susceptible plants. Earlier workers isolated a stilbene synthase gene (Vst1) from grapevine (Vitis vinifera L.), which has subsequently been introduced as a transgene into a range of species to increase resistance of host to pathogens to which they were originally susceptible. Papaya (Carica papaya L.) is susceptible to a variety of fungal diseases, including root, stem, and fruit rot caused by the pathogen Phytophthora palmivora. Since resveratrol at 1.0 mM inhibited in vitro mycelium growth of P. palmivora, we hypothesized that papaya resistance to this pathogen might be increased by transformation with the grapevine stilbene synthase construct pVst1, containing the Vst1 gene and its pathogen inducible promoter. Multiple transformed lines were produced, clonally propagated, and evaluated with a leaf disk bioassay and whole plant response to inoculation with P. palmivora. We found RNA transcripts of stilbene synthase and resveratrol glycoside were induced in plant lines transformed with the grapevine pVst1 construct shortly after pathogen inoculation and that the transformed papaya lines exhibited increased resistance to P. palmivora. The immature transformed plants appear normal and will be advanced to field trials to evaluate their utility.