Studies on Transgenic Rice with Heat-shock Inducible Expression of Hd3a Gene

Hd3A(HEAdIng dATE 3A)基因是光周期诱导水稻开花过程中的一个关键调控基因,它在短日条件下表达并促进水稻开花.通过根癌农杆菌介导的方法将热激诱导表达的Hd3A基因转化到水稻品种日本晴中.热激处理转基因植株后,检测结果表明,叶片中转基因Hd3A的表达水平比热激前显著提高,随后又下降到热激前的水平,说明转基因Hd3A在水稻中可以被热激诱导瞬间的表达.长日条件下热激转基因水稻可成功诱导其抽穗,而同样处理的野生型植株不能抽穗,表明Hd3A的瞬间表达可诱导水稻开花,且其开花的早晚与热激处理的强度有关.Hd3a(Heading date 3a)plays a key regulatory role in the photoperiod flowering pathway of rice(Oryza sativa).In this study,a heat-shock inducible Hd3a gene was transformed into wild-type rice mediated by Agrobacterium tumifaciens.The result of real-time PCR analysis showed that the expression level of transgene Hd3a increased significantly after heating treatment,and soon decreased to the background level,which suggested that Hd3a expression can be induced transiently to a very high level.In the long-day condition,the flowering of transgenic rice can be induced by heating treatment,while wild type plants can not flower with the same treatment.It proved that a transient expression of Hd3a could induce transgenic rice to flower.There was a positive correlation between flowering time and heating treatment times.福建省青年人才项目(2006F3123);霍英东教育基金(111026)资

在具有Cu衬底层的Si（111）面上自组装Co团簇的研究

Nanodots as low dimensional surface structures exhibit interesting physical properties which can be exploited in numerous applications such as a single electron transistor, optoelectronic- and magnetic storage-devices etc. Since the top-down techniques used currently are reaching their limits, the bottom-up self-assembly is probably the most promising technique for the growth of nanoscale systems due to the striving of a system toward a minimal energy and the formation of nanosized structures down to the atomic level. Nevertheless, controlling and tailoring the size and distribution of these nanodotes for possible devices is a challenge and requires a thorough knowledge of the complex interaction between atoms and surface. Since cobalt is regarded as one of the most important elements used in magnetic materials for magnetic or magneto-optical devices and silicon is the key element used in the semiconductor industry, the combination of these two materials will promote the development of materials and devices for next-century magnetoelectronics. However, it is known that Co reacts easily with Si even at room temperature [1]. Nevertheless, recent works have shown that a buffer layer still strongly affects the surface diffusion of deposited atoms and the subsequent island nucleation [2-5]. Annealing of monolayer (ML) amounts of Cu on Si(111) leads to an (5.55×5.55) periodic reconstruction with excellent thermal stability. Although the Cu/Si(111) layer does not exhibit a true long range periodicity, its good stability, together with the significant removal of the Si dangling bonds, indicates that it is a good template for the fabrication of self-assembled Co nanoclusters. As far as we know, there are few studies of Co/Cu/Si(111) system. The present study provides the structural property of self-assembled Co nanoclusters on Cu/Si(111) surface using scanning tunneling microscopy (STM). STM and LEED results show that the Co nanolusters changes not only in the island size but also in the island shape and structures on the top of the islands with increasing substrate temperature from room temperature to 830K during deposition. It was confirmed that the ultrathin buffer layer on Si (111) surface has a significant influence on the surface morphology after subsequent depostiong of Co. On one hand it can partly prevent Co to form Co silicide. On the other hand the diffusion of Co atoms on the surface can be greatly enhanced. [1] J. M. Phillips, J. L. Batstone, J. C. Hensel, I. Wu. M. Cerullo, J. Mater. Res. 5, 1032 (1990). [2] X. Liu, T. Iimori, K. Nakatsuji, and F. Komori, Appl. Phys. Lett. 88, 133102 (2006). [3] T. Schmidt, J. I. Flege, S. Gangopadhyay, T. Clausen, A. Locatelli, S. Heun, and J. Falta, Phys. Rev. Lett. 98, 066104 (2007) [4] P. Aivaliotis, L. R. Wilson, E. A. Zibik, J. W. Cockburn, M. J. Steer, and H. Y. Liu, Appl. Phys. Lett. 91, 013503 (2007). [5] Y. Takagi, A. Nishimura, A. Nagashima, and J. Yoshino, Surf. Sci. 514, 167 (2002). Keywords: STM, Si surface, Co silicide, nanoclusters