Chow, W. S. | bioRxiv Science

bioRxiv2024

A negative correlation between the rate coefficient of repair after photoinhibition of cold acclimated plants and the mean annual temperature of the habitats of Arabidopsis thaliana ecotypes

Both the activity of photosynthesis and the repair of damaged photosystems decline in cold environments, which may increase the extent of the damage of photosynthetic machinery by light, namely photoinhibition. We hypothesized that plants in colder habitats may possess greater tolerance to photoinhibition, especially in low temperature conditions. We measured the rate of photoinhibition, rate of photoinhibition repair and other thylakoid activities in cold environments using 298 Arabidopsis thaliana ecotypes and studied the relationships among the indicators of photoinhibition tolerance and climatic data of the habitat of each ecotype. The plants acclimated to cold conditions (12{degrees}C) for three days showed a negative correlation between the rate of photoinhibition repair at 5{degrees}C and the mean annual temperature of habitats, although we could not see this correlation with the control plants grown in 22{degrees}C. This result would indicate that the acclimation capacity of photoinhibition tolerance in cold conditions can affect the distribution of plants especially in colder regions.

plant biology↗

bioRxiv2021

The prevalence, predominance, and metabolic potentials of Candidatus Prochlorobium terpiosii in the coral-killing sponge, Terpios hoshinota

Terpios hoshinota is a ferocious, space-competing sponge that kills a variety of stony corals by overgrowth. Outbreaks of this species have led to intense coral reef damage and declines in living corals on the square kilometer scale in many geographical locations. Our large-scale 16S rRNA gene survey across three oceans revealed that the core microbiome of T. hoshinota included operational taxonomic units (OTUs) related to Prochloron, Endozoicomonas, Pseudospirillum, SAR116, Magnetospira, and Ruegeria. A Prochloron- related OTU was the most dominant cyanobacterium in T. hoshinota in the western Pacific Ocean, South China Sea, and Indian Ocean. The complete metagenome-assembled genome of the Prochloron-related cyanobacterium and our pigment analysis revealed that this bacterium had phycobiliproteins and phycobilins and lacked chlorophyll b, inconsistent with the iconic definition of Prochloron. Furthermore, the phylogenetic analyses based on 16S rRNA genes and 120 single-copy genes demonstrated that the bacterium was phylogenetically distinct to Prochloron, strongly suggesting that it should be a sister taxon to Prochloron; we therefore proposed this symbiotic cyanobacterium as a novel species under a new genus: Candidatus Paraprochloron terpiosii. With the recovery of the complete genome, we characterized the metabolic potentials of the novel cyanobacterium in carbon and nitrogen cycling and proposed a model for the interaction between Ca. Pp. terpiosi LD05 and T. hoshinota. In addition, comparative genomics analysis revealed that Ca. Paraprochloron and Prochloron showed distinct features in transporter systems and DNA replication. ImportanceThe finding that one species predominates cyanobacteria in T. hoshinota from different geographic locations indicates that this sponge and Ca. Pp. terpiosi LD05 share a tight relationship. This study builds the foundation for T. hoshinotas microbiome and paves a way for understanding the ecosystem, invasion mechanism, and causes of outbreak of this coral-killing sponge. Also, the first Prochloron-related complete genome enables us to study this bacterium with molecular approaches in the future and broadens our knowledge of the evolution of symbiotic cyanobacteria.

ecology↗