濒危红树杂交种海南海桑的杂种劣势与其根际微生物的关联分析

Association between rhizosphere microbiome and hybrid weakness of the endangered mangrove hybrid plant Sonneratia×hainanensis

【目的】研究杂交物种与亲本的形态生理特征差异,有助于理解物种的形成和进化机制。【方法】植物学研究发现红树植物杯萼海桑(Sonneratia alba)和卵叶海桑(Sonneratia ovata)的自然杂交后代海南海桑(Sonneratia×hainanensis)表现出明显的生长劣势,本研究通过Illumina高通量测序技术,分析杂交后代与亲本根际微生物细菌与真菌群落差异,解析子代杂种劣势原因。【结果】主坐标分析表明,虽然3种植物根际细菌和真菌群落不存在显著差异,但子代海南海桑根际群落结构和组成与生存力较强的母本差异较大,与父本更为相似。物种组成分析表明,细菌分布于76门320科388属,优势的假单胞菌门(Pseudomonadota)在3种植物根际相对丰度都超过41.00%,其中子代丰度为55.33%,高于其亲本。属水平上,脱硫球菌属(Desulfococcus,3.23%)和红游动菌属(Rhodoplanes,0.94%)等18个共有属占据测序总量15.77%,但在子代中,8个耐盐菌属的丰度明显降低,如深海弯曲杆菌属(Mariprofundus),可能影响到子代的盐耐受性。真菌群落中的子囊菌门(41.89%)与担子菌门(4.53%)为优势菌门,但在子代中的丰度均显著低于亲本,并且特征优势属也不同。原核生物分类单元功能注释(functional annotation of prokaryotic taxa,FAPROTAX)功能预测发现,红树林的原核微生物参与了硫代谢和氮代谢过程,但在细菌群落中,虽然子代的Shannon指数和Simpson指数均显著高于母本,但母本中一些与氮循环相关的高丰度类群并未在子代中得到继承,如B-42(unclassified Trueperaceae)、Mariprofundus和氧化硫单胞菌属(Sulfurimonas)。土壤理化性质也显示,子代全氮和全磷的含量均显著低于其母本,一些与氮含量呈显著正相关的类群,如细菌中的Mariprofundus和B-42,真菌中的曲霉属(Aspergillus)和红酵母属(Rhodotorula),在子代中均有所减少。【结论】本研究有助于从土壤根际微生物视角进一步了解海南海桑的杂种劣势原因。

[Objective]To study the morphological and physiological characteristics of hybrids compared with their parents and contribute to research on the mechanisms of speciation and evolution.[Methods]Sonneratia×hainanensis,a natural hybrid of the mangrove plants Sonneratia alba and S.ovata,usually presents hybrid weakness than its parents.In this study,Illumina high-throughput sequencing was employed to compare the rhizosphere microbiomes(including bacteria and fungi)between the hybrid and its parents,on the basis of which the reason for hybrid weakness was explored.[Results]The principal coordinate analysis(PCoA)revealed no significant difference in the rhizosphere bacterial or fungal community structure between the hybrid and its parents.However,the rhizosphere microbiome of the hybrid was different from that of the female parent S.alba with strong survival ability but similar to that of the male parent S.ovata.The rhizosphere bacteria belonged to 388 genera,320 families of 76 phyla.The dominant phylum Pseudomonadota had the relative abundance above 41.00%in the rhizosphere of the three plant species,reaching 55.33%in the hybrid,which was higher than that in the parents.At the genus level,18 common genera including Desulfococcus(3.23%)and Rhodoplanes(0.94%)in all the three mangrove plants showed the relative abundance of 15.77%.Among them,8 salt-tolerant genera such as Mariprofundus showed decreased relative abundance in the hybrid,which may affect the salt tolerance.The rhizosphere fungi were dominated by Ascomycota and Basidiomycota with the relative abundance of 41.89%and 4.53%,respectively,which was significantly lower than that in the parents.Moreover,the predominant fungal genera were different in the three mangrove plants.Functional annotation of prokaryotic taxa(FAPROTAX)predicted that the mangrove prokaryotes were involved in sulfur metabolism and nitrogen metabolism.Although the hybrid had higher Shannon and Simpson indexes of rhizosphere bacteria than S.alba,some dominant taxa such as B-42(unclassified Trueperaceae),Mariprofundus,and Sulfurimonas participating in the nitrogen cycle were not inherited by the hybrid.The soil total nitrogen(TN)and total phosphorus(TP)of the hybrid was significantly lower than that of S.alba.TN was significantly positively correlated with the relative abundance of Mariprofundus,B-42,Aspergillus,and Rhodotorula,which,however,demonstrated decreased relative abundance in the rhizosphere of the hybrid.[Conclusion]The results help to understand the mechanisms of hybrid weakness in Sonneratia×hainanensis.