肠道细菌对小线角木蠹蛾克服中国白蜡防御物质的影响

植物受到植食性昆虫危害后将产生大量有毒性的化学防御物质提高自身抗性。为了探究小线角木蠹蛾幼虫肠道细菌在克服中国白蜡防御物质的作用,利用高效液相色谱法,明确了小线角木蠹蛾危害中国白蜡对其韧皮部中毛蕊花糖苷含量的影响;通过饲料混毒法,研究了毛蕊花糖苷对小线角木蠹蛾的作用;采用传统培养技术和16S rDNA高通量测序技术,探究抗生素清除小线角木蠹蛾幼虫肠道细菌的作用;利用活体和离体试验,对幼虫肠道细菌降解毛蕊花糖苷的能力进行研究。结果表明:(1)小线角木蠹蛾幼虫危害寄主中国白蜡导致其韧皮部中毛蕊花糖苷的含量升高。(2)毛蕊花糖苷不仅抑制幼虫正常生长,对幼虫还有毒杀作用。(3)抗生素可以将幼虫肠道内细菌完全清除。(4)发现小线角木蠹蛾幼虫肠道细菌具有降解毛蕊花糖苷的能力,其中沙雷氏菌属(Serratia sp.)和类香味菌属(Myroides sp.)降解能力最强,可降解100%毛蕊花糖苷。

基于植物代谢组学和昆虫肠道细菌分析光肩星天牛的寄主适应性

为探究光肩星天牛Anoplophora glabripennis对传统抗性树种白蜡的适应性机制,利用代谢组学分析不同白蜡品种木质部次生代谢产物,利用16S rRNA测序技术对取食白蜡后的光肩星天牛肠道细菌群落组成进行检测,并采用Pearson方法分析两者的相关性。结果表明,在洋白蜡Fraxinus pennsylvanica和中国白蜡F.chinensis木质部中共筛选出27类抗虫性差异代谢产物,其中黄酮苷、双黄酮及多黄酮、简单酚类、香豆素及其衍生物和木质素苷在中国白蜡中含量较丰富;而2-芳基苯并呋喃类黄酮、阿朴啡类、麦角林及其衍生物和有机氮化合物在洋白蜡中占优。光肩星天牛取食洋白蜡和中国白蜡2种寄主后肠道细菌群落组成存在明显差异,优势菌门分别为变形菌门和厚壁菌门;优势菌属分别为拉乌尔菌属Raoultella(55.79%)和乳球菌属Lactococcus(57.52%);筛选到21个差异菌属,其中13个菌属在中国白蜡中的相对丰度显著高于洋白蜡。相关性分析结果表明,尽管类黄酮、简单酚类、香豆素及其衍生物和木质素苷等酚类化合物在中国白蜡中含量更高,但取食中国白蜡后光肩星天牛肠道内一方面存在优势菌群参与代谢上述物质,如肠球菌属Enterococcus、拉乌尔菌属对类黄酮和木质素苷的代谢;另一方面中国白蜡通过一些特异菌属和共有菌属的增殖参与代谢,如乳杆菌属Lactobacillus和放线菌属Actinomycetes对类黄酮、乳球菌属对简单酚类、鞘氨醇杆菌属Sphingobacterium对香豆素及其衍生物、放线菌属和肠球菌属对木质素苷的代谢。生物碱在中国白蜡中的含量低于洋白蜡,未发现特殊菌属降解该类物质。推测相对于洋白蜡,取食中国白蜡后光肩星天牛肠道菌群更具特异性和多样化,可以帮助光肩星天牛快速代谢相关次生物质,顺利完成其在中国白蜡上的生活史。

The spatiotemporal characteristics of spring phenophase changes of Fraxinus chinensis in China from 1952 to 2007

We selected widely distributed and well observed plant species Fraxinus chinensis to study the formation mechanism of geographical distribution of the plant phenophase changes and revealed their spatiotemporal dynamics in China. Based on the first leaf date （FLD） data at 12 sites derived from Chinese Phenological Observation Network （CPON） and related meteoro- logical data, we developed and validated the process-based model of FLD for Fraxinus chinensis. After reconstructing data series of FLD for Fraxinus chinensis over the study area from 1952 to 2007, we analyzed different spatiotemporal patterns of phenophase changes of this species. The results suggested that the process-based model was able to simulate the FLD accu- rately for Fraxinus chinensis on large spatial and temporal scales, because of the consideration of different budding rate re- sponded to the air temperatures during the dormancy and the quiescence in accordance with the physiological mechanism of plants. The geographical distribution of the spring phenology in temperate regions was determined by the spatial pattern of daily average air temperature. The changes of FLD for Fraxinus chinensis revealed significant phenological advances in most areas. However, it showed delayed trends in a few sites. The overall average change trend was -1 .l days/decade. This result was consistent with the advanced trend in other regions of the North Hemisphere. The changes of FLD showed a noticeable regional variation with clearer advance in the north than in the south. The FLD in northern China showed an average ad- vance as high as -2.0 days/decade （P〈0.01）. And the advance in northeastern and northwestern China was respectively -1.5 and -1.4 days/decade （P〈0.01）. Furthermore, eastern and central regions showed a minor trend, which was -1.0 days/decade （P〈0.05）. The smallest and non-significant advance appeared in southwestern and southern China.