新疆极端盐渍环境一年生藜科盐生植物-异子蓬幼苗迟滞发育机理研究

The seedling stage is the most fragile and vulnerable stage in life cycle of the annual plant, it may determine the survival of individuals and reproduction and thriving of the populations. Plant species which can survive adverse circumstances must have developed successful adaptation strategies in seedling stage. To explore the mechanism of seedling survival of adversity is of great significance for us to understand the unique strategy of plant to stress environment in the whole life cycle. However, so far, the understanding to mechanism of salt tolerance of seedling, especially the survival strategy of seedling in extremely adverse habitats, is far from enough. Suaeda aralocaspica is an annual halophyte distributed in extremely saline environment in Xinjiang desert, we found in field investigation that its seedling presented a phenotype of significantly developmental delay in high salinity (concomitant with other stresses) environment, this characteristic is closely related to the adaptability of the seedling to harsh habitat. So, in the present project, based on our previous investigation we plan to study on phenomenon of seedling developmental delay of S. aralocaspica at three different aspects as: inner micro-structure basis, physiological and biochemical responses, and different expression levels of relevant genes under salt stress, by observation of cellular/subcellular structure in seedling development; assay of the key parameters on photosynthesis, antioxidant system, osmosis regulation system, and phyto-hormone; analysis of gene response by cDNA-AFLP and 2-D gel electrophoresis techniques. With these work we expect to gain an insight into the mechanism of seedling developmental delay of the annual halophyte- S. aralocaspica, and its correlation with salt (adverse) tolerance, and finally provide theoretical evidence for improvement of saline-alkaline land in Xinjiang.

幼苗是一年生植物生活周期中最脆弱的阶段，它决定着植物个体的生存和种群繁衍。能在逆境下生存的植物，必然具有其成功的苗期适应对策。而对此进行探索将对我们深入理解植物整个生长周期应对逆境的独特策略具有重要意义。然而目前对植物苗期耐盐机制特别是极端环境幼苗的生存基础研究很有限。异子蓬是分布于新疆极端盐渍荒漠的一年生盐生植物，调查发现其幼苗在高盐（伴随其他胁迫）生境中有着显著迟滞发育的表型特征，这与其幼苗对恶劣生境的适应密切相关。鉴于此，本项目基于前期研究基础，拟通过发育中细胞/亚细胞结构观察；光合、抗氧化、渗调系统及激素水平关键指标测定；相关基因应答的cDNA-AFLP及双向电泳技术分析等方面，开展盐胁迫下异子蓬幼苗迟滞发育的内在结构基础、生理生化响应、相关基因不同水平应答三个不同层面的研究，期望初步阐明一年生盐生植物异子蓬幼苗迟滞发育机制及其与耐盐（逆）的相关性，并为新疆盐碱地改良提供理论依据。

异子蓬是新疆极端盐渍荒漠的一年生盐生植物，调查发现其幼苗在高盐生境中有显著迟滞发育的表型。本项目通过幼苗发育的形态结构观察、光合/抗氧化/渗调系统关键指标和激素水平测定、幼苗发育过程的基因响应等的研究，初步阐释了一年生盐生植物异子蓬幼苗迟滞发育机制。主要结果如下：① 异子蓬幼苗随发育及盐胁迫下的形态结构观察显示，非处理幼苗形态结构变化不明显；高盐胁迫下异子蓬幼苗生长点叶原基发育较对照快；盐胁迫下子叶结构变化不明显；根部木质部数量随盐浓度升高而增多。② 异子蓬幼苗不同发育时间子叶的渗调系统、抗氧化系统、光合关键酶活性测定结果显示，除了叶绿素含量和PEPC酶活性显著升高，各系统的关键指标均呈降低趋势或不变，特别是渗调质和抗氧化酶等指标。对盐胁迫下幼苗中四种激素水平的测定显示，GA、IAA在整个测定期含量较高，ZT 总含量较低；ABA在整个幼苗期子叶中的含量均较低且不稳定。高盐具有降低激素含量的趋势。③ cDNA-AFLP技术对基因的差异表达分析显示：从异子蓬幼苗中共获得312个有同源序列的差异片段（TDFs），从中选取了30多个进行转录水平分析（qPCR），结果显示多数基因的表达随子叶的发育呈上升趋势，特别是与生长、光合及盐胁迫相关的基因。其结构、生理、激素水平及基因表达趋势分析暗示，随幼苗的发育其抗逆结构增强，而渗调及抗氧化系统等逆境相关指标活性逐渐降低，生长激素在子叶中维持相对稳定水平，且调节子叶生长活力的基因上调表达，从而使子叶能够合成更多产物提供幼苗快速生长发育以及形态建成之需。也由此反映出幼苗阶段的子叶对异子蓬植株发育有重要作用。④ 异子蓬幼苗的净光合率显著高于藜科盐生植物费尔干猪毛菜；其PEPC酶活性随盐浓度呈显著上升且呈单峰的日变化规律；PEPC/RUBPC比率在5-20倍之间。⑤ 通过本项目与剑桥大学植物科学系建立了互访关系；与中国农业大学武维华院士建立了联合培养博士向；共发表论文8篇，其中SCI收录3篇。培养硕、博士研究生7名，5名已获得硕士学位。