The most devastating disease currently threatening to destroy the banana industry worldwide is undoubtedly Sigatoka Leaf spot disease caused by Mycosphaerella fijiensis. In this study, we developed a transformation system for banana and expressed the endochitinase gene ThEn-42 from Trichoderma harzianum together with the grape stilbene synthase (StSy) gene in transgenic banana plants under the control of the 35S promoter and the inducible PR-10 promoter, respectively. The superoxide dismutase gene Cu,Zn-SOD from tomato, under control of the ubiquitin promoter, was added to this cassette to improve scavenging of free radicals generated during fungal attack. A 4-year field trial demonstrated several transgenic banana lines with improved tolerance to Sigatoka. As the genes conferring Sigatoka tolerance may have a wide range of anti-fungal activities we also inoculated the regenerated banana plants with Botrytis cinerea. The best transgenic lines exhibiting Sigatoka tolerance were also found to have tolerance to B. cinerea in laboratory assays.
Vitis vinifera L. cv. 'Thompson Seedless' presents a type of stenospermocarpy in grape where fertilization occurs but seeds abort and fail to develop. To unravel the molecular basis for stenospermocarpy in grapes, subtractive hybridization was carried out in order to isolate differentially regulated genes that participate in the seedlessness machinery. Two 'Thompson' lines, a seeded and a seedless, were screened during different flower developmental stages. One of the genes, that was differentially expressed between the seeded and seedless lines, was the chloroplast chaperonin 21 (ch-Cpn21). ch-Cpn21 is a 21-kDa co-chaperonin polypeptide formed by two GroES-like domains fused together in tandem. Silencing of ch-Cpn21 in Nicotiana benthamiana plants resulted in leaf stunting, chlorosis, as well as ovary necrogenesis leading to seed abortion. Moreover, organ-specific silencing of ch-Cpn21 only in Lycopersicum esculentum fruits resulted in the development of seedless tomatoes. These results suggest that ch-Cpn21 may play a role in seed abortion in stenospermocarpic grapes.
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