The Preliminary Study On Differences In Microstructure And Gene Expression Of Key Enzymes Flavonoids And Carotenoids

In the experiment, the cultivar Cucumber sativus L. var. xishuangbannanesis Qi et Yuan and the variety Cucumber sativus L. var. Huahuang NO.5 with different heat tolerance were used as experiment materials. the miscrostructural changes of leaves stem shoot tip were observed. Differences in gene expression of leaves,stem and flesh between the four key enzyme genes of the carotenoids and flavonoids synthesis pathway were analyzed. The causes that resulted in different heat tolerance between Cucumber sativus L. var. xishuangbannanesis Qi et Yuan and Cucumber sativus L. var. Huahuang NO.5 were discussed from several aspects of cytology and molecular biology.The results were as follows:1. Anatomical features of stems Under high temperature stress, the length and diameter of cells of Cucumber sativus L. var. xishuangbannanesis Qi et Yuan were shorter than them of Cucumber sativus L. var. Huahuang NO.5, which resulted in the significant decreasing of the length and diameter of internode. Compared with Cucumber sativus L. var. xishuangbannanesis Qi et Yuan, the number of vascular bundle and vessels with secondary cell wall in the vascular bundles were more. There was significant difference between Cucumber varieties (P< 0.05)2. Anatomical features of leaves (thickness of leaves, palisade tissue and spongy tissue)The thickness of leaves and the thickness and arrangement pattern of palisade and spongy tissues were observed by sections. The results showed, under high temperature stress, the cells of the palisade and spongy tissues in Cucumber sativus L. var. xishuangbannanesis Qi et Yuan were denser than the other. But there was significant difference among the thickness of leaves, the thickness and layer number of the palisade and spongy tissues (P<0.05)3. Anatomical features of shoot tipsUnder high temperature stress, new leaf and floral primordia were differentiated from shoot apical meristem (SAM). But the numbers of Cucumber sativus L. var. Huahuang NO.5 were significantly less than the other. Because of decreasing elongation of cells, the differentiated primordia of Cucumber sativus L. var. Huahuang NO.5 had no extension. Compared the shoot tips of them, we found that the ratio of apical meristem and primordia around significantly decreased in Cucumber sativus L. var. Huahuang NO.5, and the opposite in the other. In staining reaction, Cucumber sativus L. var. Huahuang NO.5 had lighter color of the apical meristem.4. Gene cloning of PSY, LCYb, PAL and CHS, and sequence analysisThe lengths of nucleotide sequences of PSY, LCYb, CHS and PAL were 617 bp,255 bp,455 bp and 400 bp, respectively. The analyzing results showed that the open reading frames (ORF) were 516 bp (101 bp-616 bp, encoding 171 aa),144 bp (57 bp-200 bp, encoding 47 aa),450 bp (3 bp-452 bp, encoding 149 aa) and 383 bp (18 bp-399 bp, encoding 127 aa), respectively.5. Relative expression of PSY, LCYb, PAL and CHS in different organs and tissues under high temperature stressThe expression of PSY, LCYb, PAL and CHS genes first increased and decreased afterwards in both varieties. In the 1h-5 h stress treatment, the expressions of the four genes in leaves increased faster than them in stems; in the 5h-7h stress treatment, the expressions in leaves decreased in large range. The results showed:the four genes in leaves and stems of Cucumber sativus L. var. Huahuang NO.5 showed higher expression than them of Cucumber sativus L. var. xishuangbannanesis Qi et Yuan. The expressions of the PAL and CHS genes in flesh first increased and decreased afterwards, But PSY and LCYb gene was up-regulated expression after the 5 h stress treatment. The expressions of the PSY and LCYb genes in flesh showed more fluctuation than the CHS and PAL genes, The results showed:the four genes participated in the resistance of high temperature stress, but the functional patterns varied in different varieties.