| Polyamine is a class of steroid hormones that plays an important role in plant growth and development. S-adenosylmethionine decarboxylase activity (SAMDC) is a key enzyme involved in the biosynthesis of the polyamines. The substrate for the SAMDC is S-adenosylmethionine (SAM) and the product is the decarboxylated SAM (dcSAM) which provides the aminopropyl groups for subsequent synthesis of spermidine and spermine. The purpose of this study is providing the helpful tools for understanding the physiological function of polyamines by researching the molecular characteristics and regulation of the SAMDC expression.Tomato (Lycopersicon esculentum Mill.) is ranking the top in the production area and total yield among all vegetable crops in the world and planted widely in China. The high temperature is one of the main limitary factors to stunt the normal development of tomato. If suffering high temperature, it will lead to fruiting failure, fruit abortion, production reducing and poor fruit quality. So it is important to study the heat-resistant of tomato. In our previous study, we have gotten the plantlets of ySAMDC-transformed tomato by Agrobacterium-mediated method, high temperature treated after molecular analysis, genetic analysis and horticulture characters observation. In order to learn the relationship between the overexpress of SAMDC gene and heat-tolerance in tomato, we study the changes of photosynthesis, antioxidant enzyme system and endogenous polyamines. The major study results as following:(1) A total of 46 plantlets KanR seedlings were obtained, 35 plantlets contained the 1100 bp (ySAMDC) amplification products. The frequency of PCR-positive of the KanR seedlings was 76.1%; Southern analysis showed that 9 of 11 plants contained the hybridization signals, indicating that the SAMDC gene was integrated into the tomato genome with one or two copy inserts. At the same time, we detected the expression signals of SAMDC gene in serven plants out of nine transgenetic-tomatos using Northern blotting.(2) PCR detiction of transgenic (T1 generation) 35S-b2,35S-b5,35S-b6,E8-A7,E8-M2 and non-transgenic plantlets was carried out. The plants of 35S-b6,E8-A7,E8-M2 are positive. PCR results of T1 generation transgenic tomato 35S-b6, E8-A7, E8-M2 were 8:1, 7:3, 5:1, respectively, and didn't follow the Mendelian law, which might be related to the fewer quantity of transgenic plants.(3) Analysising the expression of SAMDC gene in the fruits of seven transgenic-tomato (T0 generation) and non-transgenic plantlets. Only the fruits of transgentic plants 35S-b2 were different from the non-transgentic fruits in diameter and weight per fruit, the fruit length of E8-M2 was lower than that of contol fruit; The rigidity, the brix, the content of Vc increased a little in transgentic fruits compared with non-transgenic fruits; Lycopene contents increased notably compared with control fruits, the transgentic fruits of 35S-b2, 35S-b5,35S-b6, E8-Q4 and E8-A7 all increased more than double.(4) To study the relationship between SAMDC gene and high temperature, Five transgentic plantlets 35S-b6,E8-A7,E8-M2,35S-b2,35S-b5 (T1 generation) and non-transgenic plantlets were treated with 40°C high temperature by analysising the changes of photosynthesis, photosynthetic pigments, antioxidant enzyme system, identification of indicators relating to heat-tolerance and endogenous polyamines. Compared between before and after high temperature, non-transgentic plants changed less than transgentic-tomato in Pn, Fv/Fm and relative conductance; contrarily, the changes of non-transgentic plants were higher than transgenic plants in transpiration and Gs, but there were not similar trends in the changes of antioxidant enzyme activity, cholrophyII and carotenoid, praline, GSH and GSSG, polyamines. So more researches shoud be continued to prove the relationship between SAMDC gene and high temperature.
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