茶树根系耐酸喜铝的生理和分子机制解析

Al toxicity and low pH are major plant nutritional problems limiting crop growth on acid soils. As a pioneer crop on acid soils, roots of tea plants have the characteristics with superior tolerance to Al (Aluminum) toxicity and low pH, however, its underlying physiological and molecular mechanisms have not been elucidated yet. Previously, we found that unlike most crops, growth of tea plant roots was facilitated by Al addition at low pH. In this project, we plan to employ various tea cultivars from different acid soils as plant materials to reveal the physiological mechanisms of Al promoting tea root growth through analyzing the changes of root morphology and architecture, root anatomical structure, root exudation and nutrient efficiency. Simultaneously, we will screen the candidate genes associated with Al and acidity tolerance using transcriptomics combined with bioinformatics. The key gene (s) will be identified through functional analysis so as to explore the comprehensive physiological and molecular mechanisms underlying Al beneficial roles and high acidity tolerance of tea tree roots. The results might directly guide to improve nutrient efficiency of tea tree plants, and also could provide theoretical basis and candidate gene resources for breeding more adaptive crops to acid soils through genetic modifications.

铝毒和低pH值是酸性土壤限制作物生长的主要植物营养问题。作为酸性土壤上的先锋作物，茶树根系具有喜铝和耐酸的特性，然而，其相应的生理及分子机理还未解析。我们的前期研究发现，与大多数作物不同，酸性供铝的条件能够促进茶树根系的生长发育。本项目将以不同酸性红壤上种植的茶树品种为研究对象，通过比较酸铝处理下根系形态构型、解剖学结构、分泌物和养分效率等指标，揭示酸铝促进茶树根系生长的生理机制；同时结合转录组学分析，筛选茶树根系耐酸喜铝的候选基因，并通过功能分析确定关键基因，从生理和分子角度综合解析茶树根系耐酸喜铝的机制。研究结果对提升茶树养分效率具有直接的指导意义，同时可为提高作物酸性土壤综合适应性的遗传改良提供理论基础与候选基因资源。

铝离子能够抑制一般植物根系的伸长，是酸性土壤上限制作物生长的主要因子之一，早期研究认为铝是茶树的有益元素，能够促进茶树根系的生长。本项目通过对茶园土壤进行考察，发现茶园都只分布在酸性土壤上，因此，认为铝可能是茶树的重要元素，本项目主要开展了茶树铝浓度和时间梯度处理、根尖细胞原位观察和转录组测序分析等试验。以五种主栽茶树品种作为供试植物，总根长作为评价指标，进行铝处理水培试验，结果表明缺铝条件下茶树根系几乎不能正常生长，明确了铝是茶树根系生长发育的必需营养元素；分别利用扫描电镜与透射电镜观察茶树根尖形态结构和细胞结构的变化，使用激光扫描共聚焦显微镜对茶树根尖细胞进行morin 和TUNEL 染色的原位观察，揭示了铝能够维持茶树根尖分生区细胞DNA的稳定性；采集根尖样品进行转录组学分析，进一步探究了茶树需铝的分子机制，可能是由于铝影响核酸物质的结合，从而调控DNA 损伤和修复基因的表达。本研究成果为建设优质高效生态茶园提供了科学的理论指导，茶园不宜施用过量有机肥，会影响茶树根系的正常生长。