Identification of physiological functions of isoprene emission

像杨树这样的树木会合成并释放大量的挥发性碳水化合物异戊二烯，而草本植物则是低排放的异戊二烯。植物异戊二烯生物合成的一个功能是提高叶片在高温时期的耐温性。由于杨树杂交种是重要的林业植物，由于异戊二烯合成酶基因是从杨树中获得的，并且这些树是可转化的，因此旨在证明异戊二烯的形成作为一个性状在克服高温胁迫条件下的作用，并提供耐热性增强的杨树品系。首先，通过选择性地导入(I)异戊二烯生物合成的起始基因或(Ii)在35S CaMV启动子和/或叶组织核编码的光合作用特异启动子后面克隆的新近从白杨中分离的异戊二烯合成酶，将获得和筛选出过表达异戊二烯生物合成基因的杨树品系。在叶片中的表达将在mRNA水平、蛋白质水平上进行控制，并通过测量异戊二烯的排放来进行控制。表型的稳定性将被研究。为了获得阴性对照植物，目的是通过RNAi技术抑制异戊二烯的排放。这些转基因植物的异戊二烯形成和耐热性将在受控的光、温度和湿度条件下与野生型植物进行比较研究。最后，将选择更适合于预计在不久的将来因全球变暖而更频繁发生的发热期的菌株。

Trees like poplar synthesize and emit high amounts of the volatile carbohydrate isoprene, whereas herbs are low isoprene emitters. One function of isoprene biosynthesis in plants is to increase the temperature tolerance of leaves during periodes of high temperature. As poplar hybrids are important plants in forestry, as the isoprene synthase gene is available from poplar and as these trees are transformable, it is aimed to prove the role of the isoprene formation as a trait to overcome heat stress conditions and to deliver poplar strains with an increased thermotolerance. Initially, transgenic poplar lines will be produced and selected that over-express genes of the isoprene biosynthesis by introducing alternatively (i) an initial gene of the isoprene biosynthesis or (ii) the isoprene synthase recently isolated from P. alba x tremula cloned behind the 35S CaMV promotor and/or leaf tissue nuclear coded photosynthesis specific promotors. The expression in the leaves will be controlled on mRNA level, on protein level and by measuring the isoprene emission. The stability of the phenotype will be studied. To obtain negative control plants it is aimed to suppress isoprene emission by the RNAi technique. Isoprene formation and the thermotolerance of these transgenic plants will be studied under controlled light, temperature and humidity conditions in comparison to the wildtype. Finally strains will be selected that are better adopted to heat periods expected to occur more frequently in the near future due to global warming.