不同根构型杉木能否通过根系挥发物介导根系亲缘识别？

Previous studies found that there was a similar phenomenon of "root kin recognition" between different geographical and ecological genotypes of Chinese fir. Accordingly, in order to verify the conception of the kin recognition between neighboring Chinese fir seedlings can be mediated by root-emitted volatile organic compounds (VOCs), the two root architectures of 'umbrella type' and 'inverted umbrella type' of Chinese fir genotypes are used as experimental materials in this project. We supply the tested seedlings with three phosphorus (P) levels, and set up two P competitive environments with the same kind of root architectures to form a 'neighbors kinship relations' and different root architectures to form 'non-neighbor kinship relations', after feeding the two neighboring plants with 13C and 14C isotope gas respectively. Based on the root culture system designed independently, the technologies of VOCs situ collection and C isotope tracers are used to analyze the root system in situ and physiological process of the tested seedlings. We determine the amount and types of VOCs in the soil released by the neighboring plants under different treatments and the 13C and 14C content in plants, using isotope tracer technique and the in collecting VOCs situ, and detect the physiological and metabolic changes, such as endogenous hormones, glycolytic pathway, and so on. The above conception will be verified after analyzing the root growth taxis by adjusting the spatial architecture. Therefore, it is uncovered for the internal mechanism on kin recognition behavior between the root systems of Chinese fir genotypes with different root architecture under P competition conditions. This study will provide a scientific basis for revealing the interesting natural evolutionary mysteries of kin recognition behavior in plants and conducting the rational allocation and high-efficient cultivation of Chinese fir plantation.

前期研究发现不同地理生态类型杉木之间存在类似“根系亲缘识别”的现象，据此，我们提出猜想：不同地理生态类型杉木能够通过根系挥发物介导根系亲缘识别。为验证这个猜想，本项目选择不同根构型杉木为材料，分别构建“亲缘邻居关系”和“非亲缘邻居关系”的磷素竞争环境，采用自主设计根箱培养系统，利用原位收集根系挥发物及C同位素示踪等技术，通过根系原位观测系统和生理过程分析手段，测定分析双方对亲缘/非亲缘根系释放C源化学信息物质的吸收和分配，探讨不同根构型杉木对根系亲缘识别的信息物质的感知与交流通讯能力，分析不同组织磷转运蛋白、内源激素、糖酵解等生理代谢指标的变化，结合不同杉木根系形态学特征和生物量分配格局的变化，阐明不同邻株亲缘关系中根系的生长趋向性，揭示出杉木通过根系挥发物介导根系亲缘识别的内在机理，为进一步阐明植物亲缘识别这一有趣的自然进化奥秘，以及杉木人工林“种内混交”合理配置及高效培育提供科学依据。

杉木(Cunninghamia lanceolata)作为分布我国南方17个省区的速生造林树种，因生境差异大及生态遗传隔绝，在长期系统发育过程中形成了不同的地理生态类型。特别是南方红壤中有效磷易被Fe2+、Al3+等固定，造成土壤有效磷含量低，形成了不同地理态类型杉木对土壤磷素不足的不同适应性。为揭示杉木根系对土壤有限磷素资源的竞争及觅食机制，前期研究发现不同地理生态类型杉木之间存在类似“根系亲缘识别”的现象，据此，我们提出猜想：不同地理生态类型杉木能够通过根系挥发物（VOCs）介导根系亲缘识别。为验证这个猜想，本项目选择不同杉木无性系幼苗为材料，构建“亲缘邻居关系”和“非亲缘邻居关系”的磷素竞争环境，采用自主设计根箱培养系统，利用C同位素示踪等技术，研究发现：低磷处理下，非亲缘组木荷幼苗叶13C丰度分别显著高于亲缘组的No.32号杉木、近亲缘组的No.28号杉木（p<0.05）。不供磷条件下同亲缘组的根系分泌物相对表达量均为下调，而相对的非亲缘组表达量上调的化合物包括了氨基酸及其衍生物类10种、黄酮类有机物10种、有机酸类11种、醇类2种、酚类3种及其它类物质25种。通过添加1-丁烯、正癸烷模拟外源根系亲缘识别VOCs对杉木根系生理代谢的影响，在不供磷条件下分别筛选出615个、699个差异蛋白，这些蛋白主要参与了细胞过程、代谢过程、应激过程等生物过程，与苯丙素的生物合成、氰基氨基酸、淀粉和蔗糖代谢等通路密切相关。结合不同亲缘关系处理中，杉木体内抗氧化酶系统、养分分配格局等调整变化规律，表明杉木能够通过根系分泌的碳源物质来影响邻近植株，从而诱导杉木和邻株幼苗形态上的可塑性变化，对不同亲缘关系的邻株磷素竞争环境作出响应，验证了本项目提出的科学猜想，这为进一步阐明植物亲缘识别这一有趣的自然进化奥秘，以及杉木人工林“种内混交”合理配置及高效培育提供科学依据。