红树植物拟海桑及其亲本的根际细菌群落特征分析

Analysis of rhizosphere bacterial community characteristics of mangrove plant Sonneratia×gulngai and its parents

植物根际微生物群落能够从亲本传递给子代,从而影响植物的表型。野外调查发现,海桑属(Sonneratia)红树植物自然杂交杂种拟海桑在野外通常比亲本生长更为强壮,表现出极强的生存优势。为探究这一现象的原因,本研究从根际微生物角度出发,利用细菌16SrRNA基因高通量测序技术,对采自海南省东寨港的三种红树植物拟海桑(S.×gulngai)及其亲本海桑(S. caseolaris)和杯萼海桑(S. alba)的根际土壤进行根际细菌群落特征分析。结果表明,三种红树植物根际细菌群落多样性高,种类丰富,分属于30门242科351属,其中变形菌门(Proteobacteria)为最优势门,在各个样本中丰度超过40%,子代拟海桑继承亲本的根际微生物多数都属于这一类群。研究发现,子代拟海桑与两亲本的根际细菌类群组成在门水平存在显著差异,其中酸杆菌门(Acidobacteria)和放线菌门(Actinobacteria)在子代拟海桑中丰度分别为4.3%和6.5%,显著高于亲本1%~2%的含量;在亲本杯萼海桑中,丰度高达19.8%的栖热菌门(Thermi)在子代中丰度仅有1%,而热袍菌门(Thermotogae)(5%)甚至消失。总之,子代拟海桑与亲本杯萼海桑的根际微生物群落组成相对于亲本海桑表现出更大的差异性。土壤理化性质分析发现,子代拟海桑的土壤全氮(total nitrogen, TN)含量显著低于亲本,含量相差3倍以上,相关性分析表明,TN浓度与菌群中的浮霉菌门(Planctomycetes)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)丰度显著负相关。通过功能预测分析发现,子代拟海桑微生物群落中与基础代谢相关的碳水化合物、氨基酸、能量以及脂质代谢相关的功能基因丰度显著都高于亲本,表现出代谢能力的增强。本研究认为,子代拟海桑对亲本的根际土壤微生物进行了选择性继承,菌群组成更为合理,在保持菌群高度多样性的同时,一些根际促生菌的含量增加,使菌群基础代谢能力增加,更有利于子代拟海桑的生长。

Plant rhizosphere microbes can be transferred directly from mother to offspring, these vertically-transmitted organisms can affect host phenotype. Field investigation revealed that Sonneratia × gulngai, a natural hybrid of mangrove plants of the genus Sonneratia, usually grew stronger than its parents, and showed stronger survival advantage. In order to explore the reasons for this phenomenon, the offspring’s microbiome composition(S. × gulngai) was compared with its parents S. caseolaris and S. alba by the bacterial 16S rRNA gene high-throughput sequencing technology. The sediment samples were collected from the Dongzhaigang Mangrove National Nature Reserve of Hainan Island. The result showed the rhizosphere bacterial communities of the three mangroves were highly diverse and rich, and distributed into 30 phyla, 242 families and 351genera. Proteobacteria contributed to 40% of all reads and constituted the predominant members, most of the inherited rhizosphere microbiome belonged to this phylum. Significant differences were also observed at the phylum level. In offspring S. ×gulngai, the abundance of Actinobacteria and Acidobacteria was 4.3% and 6.5% respectively, which are significantly higher than parent’s 1%~2%;Thermi species were enriched to be dominant populations with relative abundances of 19.8% in the parent S. alba, but the numbers was only 1% in the offspring S. × gulngai, and found Thermotogae phylum(5%) was absent in the rhizosphere bacterial community of S.× gulngai. In short, microbiome composition differed more strongly between offspring S. × gulngai and the parent S. alba than S. caseolaris. The analysis of soil physical and chemical properties found that the soil total nitrogen(TN) content of S. × gulngai was significantly lower than that of the parent, with a difference of more than 3 times. Correlation analysis showed that the concentration of TN was significantly negatively correlated with the abundance of Planctomycetes, Actinobacteria, and Acidobacteria. Through functional prediction, some functional genes related to the basic metabolism in the offspring S. × gulngai microbial community were greatly enriched, S.× gulngai’s metabolic capacity was enhanced. These findings showed that the selectively inherited some the rhizosphere soil microorganisms from their parents, which made the offspring’s microbiome composition more reasonable and maintained higher diversity, some rhizosphere growth-promoting bacteria particularly enriched and increased the basal metabolic capacity,these changes promoted S. × gulngai to grow better than its parent.