南亚热带森林中后期优势种幼叶变红的生理生态及分子机制及其与群落演替的关系

Several typical dominant tree species, including mid-successional species (MS) and late-successional species (LS), which represent plants at two successional periods in Dinghushan subtropical forest succession of southern China, will be studied to explore the ecophysiological and molecular response mechanisms of the reddening of young leaves from heliophyte and mesophyte dominant tree species. A combination of potting experiment and controlled field trial, using technologies of plant physiology and molecular biology, will elucidate changes in physiological and molecular indices. These indices will be measured and analyzed in young leaves at different development stages (from juvenile to mature leaves at the top of branch) and under different light intensities (given by the two light gradients of crown canopy and understory in the field trial, and the two light levels of natural and shaded sunlight in the potting experiment). They will include: contents of secondary metabolites, photosynthetic pigments and xanthophyll cycle components; modelling of photosynthesis, chlorophyll fluorescence and photoprotection; relationship of anthocyanin content to the related gene expressions (CHS, DFR and ANS genes); resistance to oxidation (determined by the scavenging of free radicals DPPH and ROS); simulated photooxidation catalyzed by methyl viologen (MV); and combined physiological and molecular responses of the overexpression or down-regulation of Arabidopsis’s CHS gene to changing light intensities. This study will explain the relationship between (1) spatiotemporal dynamics of anthocyanin biosynthesis and accumulation in young leaves of dominant species and (2) community succession in middle and later successional stages of a low subtropical forest.

以鼎湖山南亚热带常绿阔叶林群落演替中后期的具有代表性的阳生和中生性优势种为材料，野外试验与盆栽控制试验相结合，应用植物生理及分子生物学技术，探讨不同光照强度下（野外选择林冠与林下两个光强梯度；盆栽控制模拟野外光强变化设置自然光照和遮光等两个光强梯度）不同叶龄幼叶（从枝条顶端的新生幼叶到成熟叶）叶片中次生代谢产物、光合色素和叶黄素组分等物质含量的变化，光合作用和叶绿素荧光及光保护的响应模式，花色素苷含量变化与其合成相关基因（CHS、DFR、ANS）表达的关系，并通过清除活性氧自由基（清除DPPH和ROS）和甲基紫精（MV）模拟光氧化等室内实验测定抗氧化能力，并结合模式植物拟南芥CHS超表达和缺失突变体植株对光强变化的生理和分子响应实验，探究阳生及中生性优势种红色幼叶在变化的光环境中的生理生态和分子响应机制，阐明南亚热带森林演替中后期优势树种幼叶中花色素苷合成与积累时空动态变化与群落演替的关系

我们的野外调查发现南亚热带森林中有1/3的木本植物（包括多数的优势乔木）由于积累了花色素苷导致幼叶呈现红色，为了进一步阐明幼叶花色素苷的积累对南亚热带森林群落演替的影响，研究了不同季节、不同生长光强下，群落演替中后期优势种幼叶和成熟叶的生理及分子响应机理。夏季，分析了两种生长光强下（100%和30%自然光），中期优势种黧蒴（Castanopsis fissa）、锥栗（Castanopsis chinensis）、木荷（Schima superba）和后期优势种华润楠（Machilus chinensis）、厚壳桂（Cryptocarya chinensis）、黄果厚壳桂（Cryptocarya concinna）幼叶光合能力和光保护潜力的变化。两种不同的生长光强下，两个演替段植物幼叶的光保护潜力（类胡萝卜素和抗氧化物质与叶绿素的比值）皆呈现出显著的差异。从低光到高光，后期种幼叶的Car/Chl和Flav/Chl（类黄酮/叶绿素）比值及综合光保护潜力均大于中期种。进一步分析两种光强（100%和30%自然光）下中期种木荷和后期种黄果厚壳桂的转录组水平响应。两个物种幼叶和成熟叶间的差异表达基因在与次生代谢产物的生物合成相关的生物学通路上的富集水平最显著。相对于成熟叶，两种植物幼叶的光合磷酸化相关基因及卡尔文循环相关酶基因的表达量普遍下调，而类黄酮途径关键酶基因的表达量普遍上调。不同光强下，类黄酮途径中的UFGT基因表达水平的变化与两种植物叶片变红的表型和花色素苷含量的变化一致，说明UFGT基因是调控两种乔木花色素苷积累和叶片变红的关键基因。结果表明花色素苷的积累对于群落演替后期优势种在环境变化条件下幼叶的成功发育及其种间竞争力的提升、种群的扩大具有重要的生态意义。已经发表了有标注的研究论文24篇，其中SCI收录论文19篇（SCI一区论文3篇，二区论文4篇）。