The fatty acid composition in the seed oil was significantly modified following the introduction of transgenes. To further enhance the desirable characteristics of rapeseed oil, it would be beneficial to develop a new approach for the simultaneous silencing of two or more target genes. Our goals in the current study were to (1) increase oleic acid to more than 75%, (2) reduce polyunsaturated fatty acids (PUFA) to about 10% and erucic acid to zero, and (3) accomplish these changes in a singletransformation event. In a single transformation, two fragments amplified from the fatty acid D12-desaturase 2 (BnaFAD2) and fatty acid elongase 1 (BnaFAE1) genes of Brassica napus were linked together to form a fusion fragment. The usion fragment was then used to assemble unique intron-spliced hairpin nterfering constructs. In the transgenic plant FFRP4-4, the expression of BnaFAD2 and BnaFAE1 genes was completely inhibited. The composition of leic acid in FFRP4-4 rose to 85%, PUFA dropped to 10% and erucic acid was undetectable. All hybrid F1 seeds obtained from the reciprocal crossing of FFRP4-4 and GX-parents (with different genetic backgrounds) contained more than 80% oleic acid, about 10% PUFA and very low, or undetectable, erucic acid. The results confirmed that the fusion fragment silencing construct can simultaneously and effectively silence the target genes on a consistent basis. The strategy provides a useful tool for detecting gene function and advancing genetic engineering techniques for the improvement of gricultural crops.

利用抑制差减杂交技术构建了20d和35d甘蓝型油菜湘油15发育种子特异表达基因的ssH文库。随机挑取单菌落进行PCR表明，文库质量较好。在20d和35dssH文库中随机挑选489个阳性克隆进行测序，获得452条高质量的表达序列标签（EST）。对序列进行Blast比对及功能注释，比较20d和35dSSH文库的基因表达谱，发现在20dssH库中参与糖代谢的基因出现频率较高，而在35dSSH库中与脂肪酸储存有关的油体蛋白家族、与脂肪酸转运有关的柠檬酸合酶、与脂肪酸合成有关的酰基载体蛋白去饱和酶等，参与油脂代谢相关基因出现频率较高。该结果对进一步研究油菜脂肪酸代谢调控的分子机制打下了基础。

In cucumber, we show salicylic acid only induce local acquired resistance (LAR), whereas acibenzolar-Smethyl (ASM) can induce LAR and systemic acquired resistance (SAR) to plant diseases. Jasmonic acid (JA) can induce local acquired susceptibility (LAS) and systemic acquired susceptibility (SAS). ASM treatment of lower first leaves leads to the accumulation of cucumber acidic class III chitinase (CHI2) in untreated upper leaves and effectively suppresses lesion formation on those leaves. In contrast, JA treatment completely suppresses CHI2 gene expression and causes plants to be more susceptible to Colletotrichum orbiculare. ASM-induced SAR can effectively antagonize the JA-induced SAS, providing a response that is midway between what would be expected with either JA or ASM by themselves.

将来源于甘蓝型油菜XYl5的Fad2与Fad1基因编码区，长度分别为349bp和426bp的两十保守序列片段连接成807bp的大片段。然后分别以正反向插入到pFGC5941干扰载体查耳酮合成酶内台子的两端．构建成RNAi载体。以期在幕耔中特录后能有效抑制Fad2与Fad1两个基因的表达。所构建的RNAi载体最终序列全长3kb，经限制性内切酶消化、PCK扩增验证和序列测定。证明目标序列与GenBank数据库中的碱基序列一致，并且为正反向插入到pFGC5941载体上。通过农杆菌介导的油幕转化，已获得油菜抗性再生植株144个。

本研究用8-10万伦琴60cor射线辐射双低油菜（B/napus）湘油15干种子，并对辐射后代进行高油酸连续选择，结果M2、M3、M4油酸含量有不同程度提高，至M5油酸含量迅速提高，多数植株油酸含量在70％以上，最高油酸含量达93．5％。对高油酸突变体M．04-855（种子油酸含量为915％）的fad，基因与网上公布的fad2基因DNA序列进行比对，发现突变体fad，基因270位的碱基G转换为碱基A，导致密码子由TGG转换为TGA（终止密码子）。这一区域是fad蛋白的beta折叠区和保守区。另外，在1044与1062的碱基突变也导致终止密码子的产生。这些结构上的变化导致fad2基因功能的丧失，使油酸不能转化成亚油酸，从而提高油酸含量。根据基因突变的分子机制，无论是碱基的转换或颠换，都需经过几次的复制，即经过几个世代才能完或，这也是在后期世代才出现高油酸变异的原因。