茉莉酸甲酯诱导大戟三萜类代谢的研究

京大戟是多年生草本药用植物,入药部分是其干燥根,但可入药的京大戟资源由于生长缓慢以及环境污染的加剧而越发匮乏,因此解决大戟资源日益紧张的问题是当今药用植物资源开发与利用方向的重要课题。京大戟含有三萜类、二萜类、黄酮类等丰富的活性成分,一些常见药用植物的有效成分是三萜类化合物,其在抗病毒、抗肿瘤、免疫调节等方面具有很好的活性。对植物萜类物质代谢起重要作用的关键酶,如3-羟基,3-甲基戊二酰辅酶A还原酶(hmgr)、鲨烯合酶(sqs)、法尼基焦磷酸合酶(fps)的基因克隆及活性研究取得了进展和突破,但通过调控萜类物质代谢途径中关键酶基因的表达来诱导终产物合成的研究鲜有报道。通过研究大戟萜类物质代谢途径进而利用基因工程手段提升目的物质的产量来解决京大戟药源短缺问题具有重要意义。该研究以大戟愈伤组织为材料,使用茉莉酸甲酯分别按时间梯度和浓度梯度进行诱导,将诱导后的愈伤组织分为两部分:一部分提取其总RNA,以actin为内参基因进行反转录,实时定量RT-PCR分析大戟三萜类代谢途径中hmgr、sqs与fps基因的相对表达差异;另一部分用于提取其总三萜并使用分光光度法进行含量测定。实时定量RT-PCR分析结果表明,茉莉酸甲酯可诱导3个基因的表达,但其表达模式不一样。相应的京大戟愈伤组织中总三萜的含量明显提高,最高可较未处理样品增加27%。研究结果可为茉莉酸甲酯促进药用植物大戟三萜类物质积累的分子机制研究提供参考。

Effects of seasonal changes on the growth and reproduction in Ficus racemosa and pollianting fig wasp mutualism system

The interaction between pollinating fig wasps(Agaonidae)and their host fig trees(Ficus)is a striking example of an obligate pollination mutualism. The reproductive allocation of female flowers resource in fig is attracting lasting interests of researchers. To verify how reproductive strategies of figs are affected by seasonal change, F. recemosa was used to analyze how the fig size, foundress numbers and reproductive resources allocation of fig-fig wasp change with seasons. We also conducted controlling introduction experiment on F. recemosa to explore how seed and fig offspring number change with foundresses number. Statistical model was used to fit the relationship between seed/wasp offspring number and foundresses number to estimate the optimal foundresses number, as well as the consequence of foundresses number in nature to fig-fig wasp reproduction. The results showed that fig size was significantly influenced by season, figs in rainy season were smaller than figs in warm dry season and cold dry season. Seasonal change also had significant impact on foundress numbers in nature, and fig bract played an important role in blocking the redundant foundresses. Our results also showed that the reproduction of fig-fig wasp varied seasonally, the number of seed and wasp offspring reached the highest in cold dry season. The results of controlling introduction experiment and statistical model showed that the relationship between foundresses numbers and seed/wasp offspring number fitted quadratic parabola model, either excessive or too few foundress was unfavourable for fig-fig wasps reproduction. The foundresses number in nature was approximately equal to optimal foundresses number. Our experimental results suggested that F. recemosa had evolved the reproductive strategies to adapt seasonal change in Xishuangbanna.