Institute of Sciences of Food Production, CNR Unit of Lecce, via Monteroni, 73100 Lecce, Italy.
Plant Physiol Biochem. 2011 Oct;49(10):1092-9. doi: 10.1016/j.plaphy.2011.07.012. Epub 2011 Jul 29.
A novel strategy to induce parthenocarpy in tomato fruits by the induction of resveratrol biosynthesis in flower tissues was exploited. Two transgenic tomato lines were considered: a higher resveratrol-producing (35SS) line, constitutively expressing a grape stilbene synthase cDNA, and a lower resveratrol-producing (LoxS) line, expressing stilbene synthase under a fruit-specific promoter. The expression of the stilbene synthase gene affected flavonoid metabolism in a different manner in the transgenic lines, and in one of these, the 35SS line, resulted in complete male sterility. Resveratrol was synthesised either in 35SS or LoxS tomato flowers, at an even higher extent (about 8-10 times) in the former line. We further investigated whether stilbene synthase expression may have resulted in impaired naringenin accumulation during flower development. In the 35SS flowers, naringenin was significantly impaired by about 50%, probably due to metabolic competition. Conversely, the amount of glycosylated flavonols increased in transgenic flowers, thereby excluding the diminished production of flavonols as a reason for parthenocarpy in tomato. We further investigated whether resveratrol synthesis may have resulted changes to pollen structure. Microscopic observations revealed the presence of few and abnormal flake-like pollen grains in 35SS flowers with no germination capability. Finally, the analysis of coumaric and ferulic acids, the precursors of lignin and sporopollenin biosynthesis, revealed significant depletion of these compounds, therefore suggesting an impairment in structural compounds as a reason for pollen ablation. These overall outcomes, to the best of our knowledge, reveal for the first time the major role displayed by resveratrol synthesis on parthenocarpy in tomato fruits.
通过在花组织中诱导白藜芦醇生物合成来诱导番茄果实单性结实的新策略得到了利用。考虑了两种转基因番茄品系：一种是具有更高白藜芦醇产量的（35SS）系，组成型表达葡萄芪合酶 cDNA；另一种是具有较低白藜芦醇产量的（LoxS）系，在果实特异性启动子下表达芪合酶。芪合酶基因的表达以不同的方式影响转基因品系中的类黄酮代谢，在其中一个品系 35SS 系中，导致完全雄性不育。在 35SS 或 LoxS 番茄花中合成白藜芦醇，在前者中的程度甚至更高（约 8-10 倍）。我们进一步研究了芪合酶表达是否可能导致花发育过程中橙皮素积累受损。在 35SS 花中，橙皮素显著受损约 50%，可能是由于代谢竞争。相反，糖基化类黄酮的量在转基因花中增加，从而排除了番茄单性结实中类黄酮产量减少的原因。我们进一步研究了白藜芦醇合成是否可能导致花粉结构发生变化。显微镜观察显示，35SS 花中花粉粒数量少且异常呈片状，没有萌发能力。最后，对香豆酸和阿魏酸（木质素和孢粉素生物合成的前体）的分析表明，这些化合物的含量显著减少，因此表明结构化合物的损伤是花粉消融的原因。就我们所知，这些总体结果首次揭示了白藜芦醇合成对番茄果实单性结实的主要作用。
