毛竹苗期对低磷环境的适应及其机理研究

Phosphate (Pi) deficiency in soils is a key factor that limits plant development. A substantial body of studies have thoroughly investigated the responses of plant to deficient soil Pi on crops and a few model plant species. However, there is still a lack of understanding on how moso bamboo (Phyllostachys edulis Carr.), native to the subtropical China where the soils are subjected to heavy Pi deficiency in soil, responded and/or get coupled with low Pi in soils. Furthermore, more information is needed on how soil microorganism activities in combination with plant physiological and biochemical courses affects the process of P utilization in this region. In the current study, moso bamboo seedlings were used to estimate their responses to the interactions between P deficiency and microorganism condition. We intended to clarify the underlying mechanism via assessing differences in seedling morphological and physiological attributes, molecular biology foundation and gene expression and the synergies of microbial combination communities. Concomitantly, we expected to explore the possibilities for moso bamboo seedlings to utilize P more efficiently, as well as to screen and isolate functional microbial populations for phosphorus utilization. The study would improve the understanding on tree plant physiology and molecular biology processes related to P efficiency, and would also be valuable to cultivate varieties of P effective and increase efficiency of P fertilizer application in bamboo seedling production.

土壤有效磷匮乏对植物生长的限制是全球关注的热点问题。我国亚热带地区普遍存在的低磷环境对毛竹生长的影响以及毛竹低磷适应机制尚不十分清楚，土壤微生物介导毛竹磷素利用的生理生态学机理知之更为匮乏。本项目拟以毛竹幼苗为研究试材，通过多梯度磷胁迫和土壤微生物环境模拟交互试验，研究毛竹苗期对低磷环境的适应机理，包括：1）形态表现及生理适应机制；2）分子生物学调控机理；3）微生物协同效应。在此基础上发掘毛竹苗木自身磷高效利用潜力，筛选分离磷利用关键功能微生物种群。预期成果将丰富植物磷营养的生理学和分子生物学知识体系，为磷高效林木品种的培育和高效磷利用技术手段的开发应用提供科学依据和技术基础。

低磷土壤环境在生态系统中是一个普遍存在的现象，我国亚热带地区普遍存在的低磷环境对毛竹生长的影响以及毛竹低磷适应策略及其微生物协同机制尚不清楚。本研究通过竹林地土壤溶磷微生物筛选与功能分析以及盆栽控制实验，从形态表现与生理适应机制、异质性磷养分影响机制、分子生物调控机制和微生物协同调控机制角度揭示毛竹苗期对低磷环境的适应机制。结果表明，不同程度低磷胁迫对毛竹分蘖生长、叶片数量及各组织生物量的影响存在差异性持续影响效应。随苗木生长阶段的推进，5 mg·kg-1土壤有效磷对毛竹地上部生长的抑制性影响逐渐减弱，而2.69 mg‧kg-1低磷土壤的抑制性影响持续加强。随着低磷胁迫环境的延续，毛竹幼苗根系生长量的增加显著大于地上部，进而提高其对磷养分的捕获能力。在异质性磷养分环境条件下，毛竹幼苗通过高磷空间内根系不断高效吸收利用磷养分，并优先运输供应地上部分生长。转录组学分析发现，16508个毛竹特异基因参与低磷调控，其中11个关键功能基因（MYC2、RHR2、PHT-1、SCL1、WRKY6、SCR、WRKY51-2、bZIP29、PHT1-8、PHT1-4、WRKY51-1）受到低磷胁迫诱导，且发现共表达转录因子MYB20、CIGR1-1、CIGR1-2和ERF110激活SCR启动子，参与毛竹低磷响应初期调控。此外，通过竹林功能性溶磷微生物筛选获得36株溶磷菌株，包括假单胞菌属、伯克霍尔德菌属、肠杆菌属、预研菌属、克吕沃尔菌属、埃希氏菌、西地西菌属、泛菌属、毛霉菌属等，其发酵液有效磷含量在185-581.33 mg‧L-1之间，且溶磷过程伴随发酵液pH降低，表明溶磷微生物活化难溶性磷养分或矿化有机磷养分过程伴随质子释放和有机酸的分泌。通过微生物菌株接种试验，发现丛枝菌根和溶磷细菌混合接种通过激发毛竹幼苗细胞进程、单细胞代谢过程、刺激反应、生物调、ATP结合、催化活性、核酸结合转录因子活性等生物功能以适应低磷胁迫，进而显著促进毛竹幼苗磷养分吸收利用与苗木生长。研究成果为毛竹磷高效利用策略及其微生物调控途径的开发提供理论依据与技术支撑。