Characterization of Molecular Diversity and Organization of Phycobilisomes in Thermophilic Cyanobacteria

Abstract

Thermophilic cyanobacteria are cosmopolitan and abundant in the thermal environment. Their light-harvesting complexes, phycobilisomes (PBS), are highly important in photosynthesis. To date, there is limited information on the PBS composition of thermophilic cyanobacteria whose habitats are challenging for survival. Herein, genome-based methods were used to investigate the molecular components of PBS in 19 well-described thermophilic cyanobacteria. These cyanobacteria are from the genera Leptolyngbya, Leptothermofonsia, Ocullathermofonsia, Thermoleptolyngbya, Trichothermofonsia, Synechococcus, Thermostichus, and Thermosynechococcus. According to the phycobiliprotein (PBP) composition of the rods, two pigment types are observed in these thermophiles. The amino acid sequence analysis of different PBP subunits suggests several highly conserved cysteine residues in these thermophiles. Certain amino acid contents in the PBP of thermophiles are significantly higher than their mesophilic counterparts, highlighting the potential roles of specific substitutions of amino acid in the adaptive thermostability of light-harvesting complexes in thermophilic cyanobacteria. Genes encoding PBS linker polypeptides vary among the thermophiles. Intriguingly, motifs in linker apcE indicate a photoacclimation of a far-red light by Leptolyngbya JSC-1, Leptothermofonsia E412, and Ocullathermofonsia A174. The composition pattern of phycobilin lyases is consistent among the thermophiles, except for Thermostichus strains that have extra homologs of cpcE, cpcF, and cpcT. In addition, phylogenetic analyses of genes coding for PBPs, linkers, and lyases suggest extensive genetic diversity among these thermophiles, which is further discussed with the domain analyses. Moreover, comparative genomic analysis suggests different genomic distributions of PBS-related genes among the thermophiles, indicating probably various regulations of expression. In summary, the comparative analysis elucidates distinct molecular components and organization of PBS in thermophilic cyanobacteria. These results provide insights into the PBS components of thermophilic cyanobacteria and fundamental knowledge for future research regarding structures, functions, and photosynthetic improvement.

Genome-scale identification and comparative analysis of transcription factors in thermophilic cyanobacteria

“…A total of 22 thermophilic cyanobacteria were compiled into the genome dataset. These thermophilic cyanobacteria were previously verified by the literatures [ 16 – 18 ]. Briefly, the 22 thermophiles were taxonomically assigned to six families, including Leptolyngbyaceae: Leptodesmis sichuanensis A121 [ 19 ] and Leptothermofonsia sichuanensis E412 [ 20 ]; Oculatellaceae: Leptolyngbya sp.…”

The Unique Light-Harvesting System of the Algal Phycobilisome: Structure, Assembly Components, and Functions

“…Their PBS is very important for the adaptation of these cyanobacteria to high-temperature environments. A comparative analysis elucidated distinct molecular components and organization of PBSs in thermophilic cyanobacteria and revealed several highly conserved amino acid sequence motifs of the PBP subunit [7]. PBPs and phycocyanin from extreme environments show great potential as antioxidant, anti-inflammatory, anticancer, antibacterial, antiplatelet, and antiviral compounds [8].…”