Functional analysis of the role of tomato (Solanum lycopersicum L.) fruit photosynthesis in metabolism and development

该项目特别关注改变水果光合作用对水果生长，代谢和成熟方面的影响。为此目的，在绿色果实特异性启动子控制下的转基因番茄植物表现出Rubisco小亚基、磷酸烯醇式丙酮酸羧化酶（PEPC）和谷氨酸-1-半醛氨基转移酶（GSA）的独立反义抑制，以及后一种酶的过表达，迄今为止的结果表明，GSA的过表达和PEPC的反义抑制对绿色果实的性能或产量几乎没有影响。成熟一般，特别是气体交换和叶绿素荧光参数。结果表明，PEPC活性低的植株淀粉和几种有机酸含量略有下降，而GSA过量表达的转基因果实中磷酸己糖含量增加，相反，GSA反义抑制导致果实叶绿素缺乏，对果实同化速率和叶绿素量子产率有明显影响。果实的特点是叶绿素a（高达90%）和类胡萝卜素含量急剧减少。然而，第一次观察并没有发现叶绿素含量下降，从而损害光合性能与成熟行为的水果之间的相关性。水果代谢的这方面和其他方面仍有待于在即将进行的实验中详细研究，包括应用广泛的生理学、分子生物学和生物化学（包括通过气相色谱-和液相色谱-质谱和通量分析的代谢物分析）方法。

Particular attention in the project is paid to the effect that altering fruit photosynthesis has on aspects of fruit growth, metabolism and ripening. To this end transgenic tomato plants, under the control of a green fruit specific promoter, exhibiting independent antisense inhibition of the small subunit of Rubisco, Phosphoenolpyruvate carboxylase (PEPC) and Glutamate-1-semialdehyde aminotransferase (GSA), as well as overexpression of the latter enzyme, were generated.Results to date have revealed that overexpression of GSA and antisense inhibition of PEPC had little effect on green fruit performance or ripening in general, in particular on gas-exchange and chlorophyll fluorescence parameters. There were slight decreases in starch and several organic acid contents in plants with lower PEPC activity, and increases in hexose-phosphates in transgenic fruits overexpressing GSA.In contrast, antisense inhibition of GSA in fruits led to chlorophyll-deficient fruit phenotype and had distinct effect on fruit assimilation rate and chlorophyll quantum yield. Fruits were characterised by drastic reduction in chlorophyll a (up to 90%) and carotenoids content. However, first observations did not revealed a correlation between the decreased chlorophyll content and consequently compromised photosynthetic performance with ripening behaviour of the fruits. This and other aspects of fruit metabolism remain to be studied in detail in forthcoming experiments including application of a broad range of physiological, molecular biological and biochemical (including metabolite profiling by gas chromatography- and liquid chromatography – mass spectrometry and flux analysis) methods.