猪毛菜属C4木本种及其C3近缘种的C4光合进化研究

More C4 photosynthesis traits have been shown to exist and develop in some C3 desert plants with increasing drought in China in our previous studies, but the evolution process of C4 photosynthesis is still unclear. Chenopodiaceae and Salsola L. is the earliest one of the families and genera for occurrences of C4 plants, and also ranks among the most ecologically pioneer important genera covered species widely distributed in China's desert regions. Therefore, C4 species and its C3 sisters are the excellent materials to discover the evolution of C4 photosynthesis in C3 plants and the origin of C4 photosynthesis in C4 plants .We are going to focus on 11 species in Salsola L.distributed naturally in northwest desert regions, respectively. For newly generated sequences, three genetic markers were PCR amplified in chloroplast genome. The clear and robust molecular phylogeny for 3 species in C4 shrubs and 8 species in their C3 sisters in Salsola L. will be built. Comparative methods were adopted to investigate the conservation and variation of morphological and anatomical characteristics (i.e. stomatal traits, photosynthetic anatomy，pollen and micro-morphological features of seed-coat, physiological traits (i.e. gas exchange and the activities and contents of C4 key enzymes) and ecological parameters (i.e. relative growth rates, leaf longevity, leaf density, specific leaf area, above- and under-biomass, seed size and 1000-seeds weight) between C4 shrubs and C3 sisters. The obtained relationships between C4 shrubs and C3 sisters would provide a clear clarify for the important morphological and anatomical, physiological and ecological elements, and environmental factors during C4 photosynthetic origin using C3 sisters as reference, which will be beneficial to compel to the evolutional experimental of C4 photosynthesis by human-driven according to above parameters and foundation. Meanwhile it would reveal different C4 evolution process among C3 sisters using C4 shrubs as reference, which will be beneficial to define C3 sisters with more evolutionary stage closed to C4 and higher similarity with C4 species in all kinds of characteristics as the potential force of C4 photosynthesis for the recovery and reconstruction across the desert vegetation.

申请者已证实荒漠C3植物随干旱加剧出现愈加显著的C4光合途径特征，但对其C4光合进化进程不清楚。藜科猪毛菜属是最早出现C4植物的科属之一，又是我国荒漠区的建群种属，本属C4种及其C3近缘种成为研究C4植物C4光合起源和C3植物C4光合进化的极好材料。拟以我国西北荒漠区11种猪毛菜属植物为研究对象，利用叶绿体DNA的3个基因为遗传标记，建立3个C4木本种与8个C3近缘种亲缘关系明晰的系统进化树，比较分析C4种及其C3近缘种保守和更新的叶气孔、光合结构、花粉和种皮等形态解剖特征、气体交换和光合酶活性等生理特征以及相对生长速率、叶寿命、比叶面积、地上下生物量及种子千粒重等生态特征，阐明C4木本种C4光合起源的重要内外因素，为人为驱动C3近缘种的C4光合进化试验提供参数支持；揭示C3近缘种的C4光合进化进程，择更多C4光合进化程度较高的C3近缘种，作为C4光合的潜在力量优先用于荒漠植被恢复和重建。

藜科猪毛菜属C4种及其C3近缘种成为研究C4植物光合起源和C3植物C4光合进化的极好材料，木本的C4种类稀少，研究猪毛菜属木本种的C4进化更有意义。为了追溯C4木本种的C4光合进化起源和探寻C3木本种的C4光合进化进程，我们在基于叶绿体rbcL基因构建的C3和C4种的亲缘关系基础上，通过DNA条形码技术进一步细化和明确了猪毛菜属各个种之间的清晰系统进化关系，解决了本研究首先需要解决的关键科学问题，为该属C4木本种及其C3近缘种提供精确分类依据。一方面我们通过比较研究C4种及其近缘的C3-C4中间种和C3种在形态结构、生理和生态特征的保守和变异，发现C3木本种天山猪毛菜的叶片解剖结构与C3-C4中间型白枝猪毛菜的结构更相似，C3-C4中间型松叶猪毛菜和C4木本猪毛菜的结构更相近，C4东方猪毛菜和准噶尔猪毛菜则是典型的C4光合结构。揭示猪毛菜属C4木本种的C4光合进化最易起源于偏C4的C3-C4中间型，其次是偏C3的C3-C4中间型，最后是C3近缘种。另一方面比较降水梯度上的蒿叶猪毛菜形态和生理生态特征也显示趋近C4光合的特征，揭示了猪毛菜属C3木本种向C4光合进化的进程是需要干旱驱动的。因此广泛分布有天山猪毛菜的新疆拜城盐水沟和和静以及集中分布蒿叶猪毛菜的青海和甘肃大部分荒漠自然保护区是猪毛菜属植物向C4光合进化的天然温床，成为我们关注的典型区域，为人为驱动C3近缘种的C4光合进化试验提供结构、生理和环境的参数支持。而天山猪毛菜和蒿叶猪毛菜可作为具有C4光合潜力的用于荒漠植被恢复和重建的备选物种。至此顺利完成了本项目的2个研究目标，同时发表研究成果8篇，其中SCI论文5篇。未来2018-2019年还将有2-3篇高质量的猪毛菜光合进化研究的SCI论文发表。