濒危红树植物红榄李濒危机制与回归引种实验研究

Lumnitzera littore (Jack.) Voigt is a species of endangered mangrove plants and listed as State Major Protected Wildlife (Category II) in China. L. littore only be found in Hainan Island in China with the few numbers and without natural renewal. It could be the first true mangrove plant going extinction without the protective research. But until now, the endangered mechanism of L. littore in China has been covered. Early experiments showed that the zero germination rate of L. littore before. Through the method of artificial supplementary pollination on the flowers of L. littore, the seeds germination rate has been obviously improved. During the lasted four years, the germinated seeds were planted in the native area, and then the seedlings were found which cannot be found in the early field investigation about ten years. Furthermore, in the laboratory, two hundreds seedlings of L. littore were cultivated through the seeds germination experiments and seedlings breeding research. Whether can we realize the restoration of the L. littore population in China by the artificial assisted breeding methods? Our team will research the endangered mechanism of L. littore of both the environmental factors and the biotic factors with the methods：field survey and location observation, control experiments, determination of physiological and biochemical indexes and molecular experiments of genecology and conversation biology. The test will be designed to analysis the geographical distribution, individual reproductive ecology, the biodiversity and population genetic background, the seeds germination characters and the rule of individual and population growth and development of L. littore. The results of the project will test the realization of L. littore repopulation in our country by the artificial germplasm resources saving technology and provide the scientific basis for the protection of endangered mangrove plants.

国家二级保护植物——濒危红树植物红榄李在我国目前仅见于海南岛，由于环境和生物的因素导致红榄李濒临灭绝。前期研究发现通过人工辅助授粉能显著降低红榄李种子空胚率，同时提高种子萌发率；萌发后的红榄李种子回种于原生地可以得到红榄李幼苗，因此人工辅助育种可能是最终实现恢复我国红榄李种群的有效手段。本项目拟从红榄李种群分布地的环境因子和生物因子两方面，采用样地调查与定位观测，控制实验、生理生化指标测定和分子验证等种群生态学和保护生物学的研究方法，分析红榄李的地理分布与种群生物学特性、个体生殖生态学特征、生物多样性及居群遗传背景，种子萌发特性、种群内个体及群体生长发育规律等内容。以阐明我国红榄李的致危机理，并据此进行红榄李的回归引种实验设计。以期通过人工种质资源挽救技术手段最终实现红榄李在我国的种群恢复和重建，为濒危红树植物资源的保护提供科学依据。

国家一级保护植物——濒危红树植物红榄李在我国目前仅见于海南岛，由于环境和生物因素导致红榄李濒临灭绝。本项目采用样地调查与定位观测，控制实验、生理生化指标测定和分子验证等种群生态学和保护生物学的研究方法，全面梳理了红榄李的致危机制：（1）红榄李为嗜热窄分布种，对温度极为敏感限制了其宜林地的范围。（2）红榄李存在严重有性生殖障碍，无性繁育不能产生新个体。（3）生境破坏，宜林地过度的人为干扰，是导致红榄李濒危的重要因素。（4）生物竞争导致花期红榄李授粉途径受阻，虫害威胁是造成红榄李种子败育的重要原因；通过人工辅助育种手段获得红榄李种子收集及幼苗繁育最优方法，设计回归引种实验，将红榄李回归引种至铁炉港和陵水原生地，并跟踪监测，发现回归引种地水系变化导致潮位过高对红榄李苗木的生长造成了一定的影响，同时造成了部分苗木的死亡。红榄李是位于高潮带红树植物，种植地高程是影响其成活的重要因素；基于叶绿体基因组信息分析红榄李在使君子科植物中的进化地位，红榄李叶绿体基因组全长159,687bp，编码130个基因，包括36个36tRNA, 8个rRNA 和 86个蛋白编码基因。与同科的榄李和拉关木叶绿体基因组比较分析发现，三个叶绿体基因组有高度保守的基因编码区、基因顺序和边界区。但基因rpl2和rps19在边界区有明显的差异。选择压主要集中于基因ycf2,ycf1和matK序列区域；通过转录组学和蛋白质组学手段揭示红榄李败育调控基因和蛋白的作用机制，筛选出12条红榄李MADS-box差异表达基因，通过过表达功能验证，LlMADS1基因参与调控花瓣和雄蕊的发育，LlMADS11影响花期。在不同育性的红榄李果实中发现23,513个差异表达基因，其中12.1%的基因与植物繁育相关；5.94%的基因与植物激素信号转导、糖代谢和氮代谢相关。共鉴定2,380个差异表达蛋白，其中1.86%与生殖发育的生物学过程密切相关。以上研究成果将为最终实现红榄李在我国的种群恢复和重建，为濒危红树植物资源的保护提供科学依据。