油菜BnrbcS基因超表达提高拟南芥种子重量和含油量

为深入分析光合作用关键酶二磷酸核酮糖羧化酶（Rubisco）小亚基在油菜等＂绿色种子＂发育过程中的作用,采用RT-PCR技术从油菜种胚中克隆了一个含Rubisco小亚基全长编码区的cDNA序列,命名为BnrbcS（GenBank登录号DQ242646）。BnrbcS编码181个氨基酸残基,其推导的氨基酸序列中包含典型的Rubisco小亚基功能域并与其他高等植物Rubisco小亚基具有很高的同源性,暗示BnrbcS基因产物与拟南芥等植物的Rubisco小亚基在结构和功能上可能十分相似。除了在叶、子叶、角果皮等光合器官中有很高表达外,BnrbcS在贮藏物质高速积累时期的未成熟油菜种子中亦有中等水平的表达,且其＂钟型＂表达模式与一些脂肪酸合成酶系基因的表达模式相类似。将NAPIN启动子驱动的BnrbcS种子特异超表达结构转入拟南芥,转化株系的种子含油量和种子重量有一定程度提高,显示BnrbcS在调控种子油脂等贮藏物质积累过程中具有作用。

Seed-Specific Overexpression of BnrbcS from Oilseed Increases Seed Weight and Oil Content in Arabidopsis thaliana

Ribulose-1,5-bisphosphate carboxylase/oxygenase（Rubisco）,which catalyzes the first step of CO 2 fixation,is the key photosynthetic enzyme.Yet the role of Rubisco small subunit in fatty acid biosynthesis and lipid accumulation in oilseeds still remains to be elucidated.To further evaluate the role of Rubisco small subunit during seed filling,a cDNA putative encoding the Rubisco small subunit gene BnrbcS was isolated from Brassica napus.BnrbcS（GenBank accession no.DQ242646）encoded a polypeptide of 181 amino acids with a typical domain of the small subunit of Rubisco（amino acids 66–175）.Alignments of amino acid sequences show BnrbcS shares high homologies with other plant rbcS,revealing its evolutionary conservation.RT-PCR analysis indicated that BnrbcS was preferentially expressed in photosynthetic organs such as leaves and cotyledons.BnrbcS was also expectedly expressed in developing seeds at moderate levels,which indicated its function in this tissue.The expression of BnrbcS during seed development exhibited a bell-shaped profile and similar to the temporal pattern of genes encoding core fatty acid synthesis enzymes.Furthermore,overexpression of the BnrbcS in a seed-specific manner in wild type Arabidopsis resulted in enhanced seed oil and average seed weight.Thus,the current study suggested a possible function of BnrbcS in augment the lipid content and yield.