Enhancement of sink activity by controling the gene expression and the activity of invertase and sorbitol dehydrogenase

以日本梨果膨大和玫瑰花瓣膨大为研究对象，研究了酸性转化酶在细胞膨大中的作用及其对基因表达的调控作用。(1)从日本梨果中克隆了两个液泡型酸性转化酶全长cDNA （PsV-AIV1, PsV-AIV2）。PsV-AIV1的早期生长与细胞分裂活跃有关，而PsV-AIV2主要与细胞增大和糖积累有关。(2)玫瑰花瓣的扩大是由蔗糖转化为己糖形成的高胀压引起的，这种胀压是随着基因表达量的增加而引起的。生长素处理可诱导活性升高。以草莓果实为材料，研究了NAD-SDH基因表达和山梨糖醇积累的调控。(1)克隆了草莓果实NAD-SDH （FaSDH）全长cDNA，并检测了其活性。与山梨糖醇-6-磷酸脱氢酶相关的基因存在，但未检测到其蛋白和活性。NAD-SDH活性动力学表明，山梨醇是由果糖还原反应合成的。(2)果糖、山梨醇或生长素处理均可刺激nadh - sdh活性。然而，它们对mrna的改变并不明显。(3) nadd - sdh mRNA由含内含子的未成熟mRNA和成熟mRNA组成。果糖、山梨醇或生长素对nadh - sdh活性的刺激依赖于转录后剪接速率的刺激。综上所述，酸转化酶和山梨糖醇脱氢酶在细胞扩大和糖积累过程中起重要作用，其活性受底物和植物激素的调控。

The role of acid invertase for cell enlargement and its regulation of gene expression were investigated using the systems of fruit enlargement of Japanese pear and of petal enlargement of rose. (1) Two full length vacuolar type acid invertase cDNA (PsV-AIV1, PsV-AIV2) were cloned from Japanese pear fruit. PsV-AIV1 related the early growth concerning active cell division and PsV-AIV2 related mainly cell enlargement with sugar accumulation. (2) The enlargement of rose petal was initiated by forming high turgor pressure which was formed by converting sucrose to hexose via the rising of invetase activity with increase of gene expression. The rising of activity was induced by auxin treatment.The regulation of NAD-SDH gene expression and the accumulation of sorbitol were investigated using straw berry fruit. (1) The full length cDNA of NAD-SDH of strawberry fruit (FaSDH) was cloned and the activity also detected. However, relating sorbitol-6-phosphate dehydrogenase the gene existed but the protein and activity were not detected. The kinetics of NAD-SDH activity revealed that sorbitol was synthesized by the reduced reaction of fructose. (2) NAD-SDH activity was stimulated by fructose, sorbitol or auxin treatment. However, there were not clear changes of mRNAs by them. (3) The mRNA of NAD-SDH were composed of the pre-mature mRNA containing intron and the mature mRNA. The stimulation of NAD-SDH activity by fructose, sorbitol or auxin depended on the stimulation of splicing rate after transcription.As described above, it was indicated that acid invertase and sorbitol dehydrogenase play an important role for the cellular enlargement and sugar accumulation and their activities were regluated by the substrates and phytohormone.