The lichen photobiont genus Rhizonema (cyanobacteria) exhibits diverse modes of branching, both false and true
The lichen photobiont genus Rhizonema (cyanobacteria) exhibits diverse modes of branching, both false and true
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地衣光生物根属（蓝细菌）表现出多种分支模式，包括假分支和真分支
DOI：
10.1111/jpy.13256
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发表时间：
2022
影响因子：
2.9
通讯作者：
Sanders William B.
中科院分区：
文献类型：
--
作者：
Masumoto Hiroshi;Sanders William B.
最近描述的根茎属是地衣共生中最重要的蓝藻伙伴之一，但其属诊断中的形态特征（T型的真实分支）似乎与一些已发表的显示错误分支的数据不一致。我们用光学显微镜研究了来自佛罗里达的两种担子地衣和一种来自日本的蓝藻生物分支和细胞分裂，包括后者的非共生培养材料。真菌生物体物种身份（Cyphhellostereum jamesianum、Dictyonema darwinianum 和 D. moorei）和光生物体属身份（Rhizonema）分别通过 ITS 和 rbcLX 序列得到证实。在所检查的所有三个菌株中，单个和成对的假分支普遍发生。假枝在坏死细胞或异形细胞附近发育，或者通过在毛状体的压缩褶皱处分离营养细胞而形成。在所检查的三种根茎菌株中的两种中观察到非横向细胞分裂，通常是倾斜的。 T型真分支有时是由这种分裂产生的，尽管分支细胞的倾斜生长常常导致不明确的分支连接。此外，Y型真枝似乎是从扭曲的细丝中生长出来的。在培养材料中，有时会从毛状体顶端释放出的单细胞或多细胞片段产生一种假分支。这些节段随后附着在细丝上并在那里生长为明显的分支。我们得出的结论是，根茎属具有相当大的形态灵活性，在单个菌株中可能具有多种分支模式。虽然真分枝或非横向分裂在可观察到时可能有助于区分根茎属和表型相似的细胞线属，但假分枝在两个属中常见，因此不能用于区分它们。
The recently described genusRhizonemais among the most important cyanobacterial partners in lichen symbioses, but its morphological characterization in the genus diagnosis—true branching of the T‐type—appears at odds with several published figures showing false branching. We investigated cyanobiont branching and cell division with light microscopy in two basidiolichens from Florida and one from Japan, including aposymbiotically cultured material of the latter. Mycobiont species identities (Cyphellostereum jamesianum,Dictyonema darwinianum, andD. moorei) and photobiont genus identity (Rhizonema) were corroborated with ITS andrbcLX sequences, respectively. Single and paired false branching occurred commonly in all three strains examined. False branches developed adjacent to necridic cells or heterocytes, or by separation of vegetative cells at compression folds in the trichome. Non‐transverse cell divisions, usually oblique, were observed in two of the threeRhizonemastrains examined. T‐type true branches sometimes arose from such divisions, although oblique growth from the branch cell often resulted in ambiguous branch junctions. Additionally, Y‐type true branches appeared to grow from contorted filaments. In cultured material, a kind of pseudo‐branch sometimes arose from single‐ or several‐celled segments liberated from trichome apices. The segments attached secondarily to filaments and grew there as apparent branches. We conclude thatRhizonemais a genus of considerable morphological flexibility, with multiple modes of branching possible in a single strain. While true branching or non‐transverse divisions, when observable, may help distinguishRhizonemafrom the phenotypically similarScytonema, false branching occurs commonly in both genera, and therefore cannot be used to distinguish them.