巨菌草不同生长时期的内生固氮菌群组成分析

Endophytic diazotrophs composition of Pennisetum sp. at different growth stages

摘要:

【背景】禾本科植物中存在着丰富的内生固氮菌资源，可为植物的生长、营养利用、增强抗逆性等起到重要的促进作用。【目的】揭示巨菌草不同生长时期根、茎、叶内生固氮细菌的组成及其变化。【方法】采用高通量测序技术对不同生长时期的巨菌草根、茎、叶内生固氮菌群进行群落分析。【结果】不同生长时期巨菌草根、茎、叶的15个样本分别得到4?6万条有效序列，主要分布在360 bp左右。根部巨菌草内生固氮菌群在成熟期最高，茎部和叶部均为拔节期最高，同一生长时期则为根>叶>茎，变化趋势与巨菌草植物样本的固氮酶活性变化趋势一致，其主要的菌群门类为变形菌门(Proteobacteria)和蓝藻菌门(Cyanobacteria)，主要核心属为克雷伯氏菌属(Klebsiella)、草螺菌属(Herbaspirillum)和慢生根瘤菌(Bradyrhizobium)。整体上看，根、叶部来源的各自微生物菌群组成较为接近，茎部来源的菌群与根部、叶部有交叉，成熟期根部的联合固氮菌群种类和丰度最高。典范对应分析表明各来源样本固氮菌群的组成主要受环境温度影响，其次为湿度和pH。【结论】不同生长时期巨菌草根、茎、叶固氮菌群的组成及丰度存在着较大的差异，本研究可为巨菌草内生固氮菌群资源的开发和利用以及种质资源库的建立提供基础依据。

Abstract:

[Background] Many endophytic diazotrophs can be found in gramineous plants and play important roles in promoting plant growth, nutrient utilization and stress resistances. [Objective] This research aims to reveal the composition and variation of endophytic diazotrophs in roots, stems and leaves of Pennisetum sp. at different developmental stages. [Methods] High-throughput sequencing technology was used to analyze the endophytic diazotrophs flora in roots, stems and leaves at different growth stages of Pennisetum sp. [Results] About 40 000 to 60 000 useful sequences were obtained from 15 samples in the roots, stems and leaves of Pennisetum sp. at different growth stages, and were mainly distributed within about 360 bp. At maturity period, the abundance of endophytic diazotrophs from the root of Pennisetum sp. was the highest whereas at jointing period, the stem and leaf samples showed the highest abundance. In the same growth period, the trend in abundances was observed thus: root > leaf > stem. This trend of variation was consistent with the trend of nitrogenase activity in plant samples of Pennisetum sp. The major bacterial communities identified belong to the Proteobacteria, Cyanobacteria and Klebsiella, Herbaspirillum, Bradyrhizobium. As a whole, the composition of the microbial community present in root and leaf samples was similar, whereas that from the stems had a cross with the roots and leaves. At maturity period, the abundance of associated nitrogen-fixing bacteria was highest in the roots. CCA analysis showed that the endophytic diazotrophs from different samples were mainly affected by environmental temperature, followed by moisture and pH. [Conclusion] There were great differences in composition and abundance of endophytic diazotrophs from roots, stems and leaves at different growth stages of Pennisetum sp. Our findings provide important information for development and utilization of endophytic diazotrophs resources from Pennisetum sp.