Whitney Spencer M, Andrews T John
Molecular Plant Physiology, Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory 2601, Australia.
Plant Physiol. 2003 Sep;133(1):287-94. doi: 10.1104/pp.103.026146.
Complete replacement, by biolistic plastid transformation, of the hexadecameric ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) of tobacco (Nicotiana tabacum) with the dimeric version from the bacterium, Rhodospirillum rubrum, resulted in fully autotrophic and reproductive tobacco plants that required high CO(2) concentrations to grow (Whitney SM, Andrews TJ [2001] Proc Natl Acad Sci USA 98: 14738-14743). Growth and photosynthesis of these plants was compared with that of nontransformed tobacco and other controls where the rbcL gene for the large subunit of tobacco Rubisco was linked to the aadA selectable-marker gene, simulating the gene arrangement of the transformants with R. rubrum Rubisco. An arrangement of the rbcL and aadA genes that gave rise to an abundant monocistronic rbcL transcript and a one-fifth as abundant bicistronic rbcL-aadA transcript had Rubisco levels and photosynthetic properties similar to those of nontransformed tobacco. Direct linkage of the rbcL and aadA genes, resulting in exclusive production of a bicistronic mRNA transcript analogous to that of the transformants with R. rubrum Rubisco, reduced transcript abundance and tobacco Rubisco content. The analogous transcript with the R. rubrum rbcM gene substituted for rbcL was not only reduced in abundance, but was also translated less efficiently. The photosynthetic rates of the transformants and controls were measured at high CO(2) concentrations, using a mass spectrometric method. The rates and their responses to atmospheric CO(2) concentration mirrored the amounts and the kinetic properties of the Rubiscos present. The contents of total nitrogen, carbohydrates, and photosynthetic metabolites of the leaves were also consistent with the content and type of Rubisco.
通过生物弹性质体转化，用来自红螺菌（Rhodospirillum rubrum）的二聚体形式完全替换烟草（Nicotiana tabacum）的十六聚体核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco），得到了完全自养且能繁殖的烟草植株，这些植株需要高浓度的二氧化碳才能生长（Whitney SM, Andrews TJ [2001] Proc Natl Acad Sci USA 98: 14738 - 14743）。将这些植株的生长和光合作用与未转化的烟草以及其他对照进行了比较，在其他对照中，烟草Rubisco大亚基的rbcL基因与aadA选择标记基因相连，模拟了用红螺菌Rubisco转化的植株的基因排列。rbcL和aadA基因的一种排列产生了丰富的单顺反子rbcL转录本和丰度为其五分之一的双顺反子rbcL - aadA转录本，其Rubisco水平和光合特性与未转化的烟草相似。rbcL和aadA基因的直接连接导致仅产生类似于用红螺菌Rubisco转化的植株的双顺反子mRNA转录本，降低了转录本丰度和烟草Rubisco含量。用红螺菌rbcM基因替代rbcL的类似转录本不仅丰度降低，而且翻译效率也较低。使用质谱法在高二氧化碳浓度下测量了转化体和对照的光合速率。光合速率及其对大气二氧化碳浓度的响应反映了所存在的Rubisco的量和动力学特性。叶片中总氮、碳水化合物和光合代谢物的含量也与Rubisco的含量和类型一致。
