Sanders William B, Hernández Maurizio, Pérez-Ortega Sergio, de Los Ríos Asunción
Department of Biological Sciences, Florida Gulf Coast University, Ft. Myers, 33965 USA, FL.
Departamento de Biogeoquímica y Ecología Microbiana, Museo Nacional de Ciencias Naturales (CSIC), Madrid, E-28006, Spain.
Am J Bot. 2025 Aug;112(8):e70080. doi: 10.1002/ajb2.70080. Epub 2025 Aug 6.
Lichen-forming fungi of genus Botryolepraria build no compact thalli, yet elevate and display algal symbionts upon their open, aerial mycelium. Although Botryolepraria occurs worldwide, the construction of its unique somatic form has not been examined in detail. We applied light microscopy and SEM to better understand how it is built and stabilized and how phycobionts are distributed during development.
Specimens were examined with light microscopy, conventional SEM, and cryo-field emission SEM. Symbiont identity was corroborated by obtaining and comparing nucleotide sequences with those in the NCBI database.
Hyphal branches grew centripetally toward clusters of algal symbionts, while other branches grew centrifugally outward before further bifurcating to produce additional hyphal branches that reoriented centripetally toward algal clusters. Anastomosis of hyphae, tip to tip or laterally via short bridging connections, occurred frequently. The lichen was irregularly but often densely covered with thread-like hydrophobic materials that resemble certain forms of plant epicuticular waxes. Repeated interpenetration of suspended algal clusters by anastomosing mycobiont hyphae separated and distributed phycobiont cells within the expanding reticulum. Fungal ITS and LSU and algal rbcL sequences suggest closest proximity of mycobiont and phycobiont to Botryolepraria neotropica and Pseudostichococcus monallantoides, respectively, for the material studied.
Anastomosis of hyphae, in regions where algae are absent and at the surfaces of expanding phycobiont clusters, stabilizes the soma of Botrylopraria as a three-dimensional lattice. The dense covering of hydrophobic materials over an open aerial mycelium suggests adaptation to avoid surface condensation and optimize gas exchange.
葡萄衣属的地衣形成真菌不会形成紧密的叶状体，但会在其开放的气生菌丝体上提升并展示藻类共生体。尽管葡萄衣属真菌分布于全球，但尚未对其独特体细胞形式的构建进行详细研究。我们应用光学显微镜和扫描电子显微镜，以更好地了解其构建和稳定方式，以及在发育过程中藻菌共生体是如何分布的。
使用光学显微镜、传统扫描电子显微镜和低温场发射扫描电子显微镜对标本进行检查。通过获取藻菌共生体核苷酸序列并与NCBI数据库中的序列进行比较，来确证共生体的身份。
菌丝分支向藻类共生体簇向心生长，而其他分支则离心向外生长，然后进一步分叉产生更多向藻类簇向心重新定向的菌丝分支。菌丝间的吻合，无论是尖端对尖端还是通过短的桥接连接进行侧向吻合，都频繁发生。地衣不规则但通常密集地覆盖着丝状疏水物质，这些物质类似于某些形式的植物表皮蜡。吻合的菌根菌丝对悬浮藻类簇的反复穿插，在不断扩展的网状结构中分离并分布了藻菌共生体细胞。对于所研究的材料，真菌的ITS和LSU以及藻类的rbcL序列表明，菌根共生体和藻菌共生体分别与新热带葡萄衣和单异极伪针球藻关系最为密切。
在没有藻类的区域以及在不断扩展的藻菌共生体簇表面，菌丝的吻合将葡萄衣的体细胞稳定为三维晶格。开放气生菌丝体上密集覆盖的疏水物质表明其适应方式是避免表面凝结并优化气体交换。
