iaaM基因在烟草花粉中的表达及其在花粉发育中的作用

试验利用花粉特异表达的启动子(Lat52)和绒毡层特异表达的启动子(TA29)引导外源生长素合成代谢基因(iaaM)在烟草花粉中表达以研究生长素在花粉发育中的作用。转Lat52-iaaM基因或转TA29-iaaM基因烟草在形态上表现出变异,如从茎上形成不定根,叶呈卷曲状等典型的生长素过量表达的性状。另外,与对照相比,转基因烟草花药中IAA水平显著增加,且植株矮化,开花期推迟,有的转基因烟草未能开花。上述现象表明:Lat52和TA29启动子的表达并不仅限于花粉或绒毡层,或者说这两个启动子的表达有些泄漏。转基因烟草的花药形状有较大的变异,早期的每个花药中花粉数明显减少,但这些花粉可被醋酸一洋红染色。所有能开花的转基因烟草均可收到种子,但收自某些转基因株系的种子不能萌发。所有这些结果表明生长素在花粉发育过程中起重要作用,过量的生长素会导致花粉发育的异常。

ABERRANT DEVELOPMENT OF POLLEN IN TRANSGENIC TOBACCO EXPRESSING BACTERIAL iaaM GENE DRIVEN BY POLLEN-AND TAPETUM-SPECIFIC PROMOTERS

Microsporogenesis offers an ideal model for studying gene expression, cell division and cell to cell communication during development. The role of auxin in pollen development was investigated in transgenic tobacco plants expressing the coding region of the iaaM gene from Pseudomonas syringae, under control of the promoters Lat-52 (pollen-specific) or TA-29 (tapetum-specific). IAA level in anther of transgenic plants increased significantly, and transgenic plants displayed morphological aberrations not solely attributable to pollen development (such as adventitious root formation on stems, epinastic leaf growth, delayed flowering). These results suggest that expression of Lat-52 and TA-29 are not strictly limited to anther. Anther shape was changed and the number of pollen grains per anther was reduced, but grains could be stained with aceto-carmine. Almost all flowering plants were fertile, although the number of flowers per inflorescence was reduced compared with the wild-type ones. These results suggest that auxin plays an important role in pollen development, and over-expressing auxin synthesis gene could result in aberrant development of pollen.