内生菌在水生蕨类植物满江红大孢子果发育过程中的结构特征和细胞响应  

Structural Characteristics and Cellular Response of the Endobacteria Within the Developing Megasporocaps of Water Fern Azolla

作　　者：吴志华[1] 郑斯平[2] 陈坚[2] 陈彬[2] 郑伟文[2] WU Zhi-Hua;ZHENG Si-Ping;CHEN Jian;CHEN Bin;ZHENG Wei-Wen(Sino-German Joint Research Institute,Nanchang University,Nanchang 330047,China;Institute of Biotechnology,Fujian Academy of Agricultural Sciences,Fuzhou 350003,China)

机构地区：[1]南昌大学中德联合研究院,南昌330047 [2]福建省农业科学院生物技术研究所,福州350003

出　　处：《农业生物技术学报》2021年第7期1378-1388,共11页Journal of Agricultural Biotechnology

基　　金：江西省主要学科学术和技术带头人资助计划(2017BCB22003);福建省农科院科技计划项目(A2012-2)。

摘　　要：水生植物满江红(Azolla)是蕨类、蓝藻(Cyanobacterium)和细菌的共生体。在满江红营养生长期,共生藻和内生菌共生于宿主的叶腔中。在满江红孢子果形成期,共生藻会移居到满江红的孢子果内。本研究借助超薄切片、荧光原位杂交和免疫金标记技术,通过荧光显微镜和电子显微镜观察,以揭示内生菌在满江红结孢期间的菌体形态特征和细胞响应。结果表明,内生菌伴随共生藻进入发育中的大孢子果并最终被定位在大孢子果顶端区域内。大约43%进入果腔的内生菌分泌胞外泡囊,有的还释放出DNA和多糖类似物等,25%的内生菌形成荚膜,17%的内生菌细胞质中累积了聚β羟基丁酸颗粒,9%的细菌呈现类似自噬性或坏死性的细胞死亡。大孢子果完全成熟时大部分的细菌栖身在类似生物被膜的基质中。本研究阐明了内生菌在宿主有性繁殖阶段形态结构特征和细胞响应,进而保持与宿主同步发育的节奏,以过渡到新的共生世代。这将为人工构建作物-微生物共生固氮体系提供新的思路。Aquatic plant Azolla is a mutualistic association among fern, Cyanobacterium and bacteria. At vegetative growth phase of Azolla, cyanobiont and bactbiont reside in the leaf cavity and symbiotically associate with the host plant. During the sexual reproduction of Azolla, cyanobiont was found to migrate into the sporocarp of Azolla. The presentt study aimed to explore the morphological and structural characteristics of the endo-bacteria during the sporocarp formation based on fluorescent microspcopic and electron microscopic observations using ultrathin sectioning, fluorescent in situ hybridazation and immno-gold labeling techniques.The results showed that the bacteria migrated into the developing sporocarp with cyanobiont and were positioned in the top area of pre-mature megasporocap. About 43% of the bacteria secreted numerous outer membrane vesicles. Some of them released DNA and fiberous polysaccharide-like substance, which became the main components of the matrix for the biofilm-like structure formed in the indusium of the megasporocarp.Around 25% bacterial cells were coated by the capsule, 17% of them accumulated poly-β-hydroxybutyrate granules in their cytoplasms, 9% of the bacteira appeared autophage-like or necrosis-like cell death. As megasporocarp matured completely, most of the bacteria were found to be inhabited in the biofilm-like matrix.These results illustrated that during the sporocarp formation of Azolla, the morphological and structural characteristics and cellular response of the endo-bactria might benefit them to keep the rhythm of the synchronous development with the host, then transfered to next symbiotic generation. Present study provides a new idea for artificial construction of crop-microbe symbiotic N2-fixing system.

关 键 词：满江红 蓝藻 细菌 超微结构 分泌 生物被膜 

分 类 号：S184[农业科学—农业基础科学] S188