Adaptation of a Cyanobacterium to a Biochemically Rich Environment in Experimental Evolution as an Initial Step toward a Chloroplast-Like State

Chloroplasts originated from cyanobacteria through endosymbiosis. The original cyanobacterial endosymbiont evolved to adapt to the biochemically rich intracellular environment of the host cell while maintaining its photosynthetic function; however, no such process has been experimentally demonstrated. Here, we show the adaptation of a model cyanobacterium, Synechocystis sp. PCC 6803, to a biochemically rich environment by experimental evolution. Synechocystis sp. PCC 6803 does not grow in a biochemically rich, chemically defined medium because several amino acids are toxic to the cells at approximately 1 mM. We cultured the cyanobacteria in media with the toxic amino acids at 0.1 mM, then serially transferred the culture, gradually increasing the concentration of the toxic amino acids. The cells evolved to show approximately the same specific growth rate in media with 0 and 1 mM of the toxic amino acid in approximately 84 generations and evolved to grow faster in the media with 1 mM than in the media with 0 mM in approximately 181 generations. We did not detect a statistically significant decrease in the autotrophic growth of the evolved strain in an inorganic medium, indicating the maintenance of the photosynthetic function. Whole-genome resequencing revealed changes in the genes related to the cell membrane and the carboxysome. Moreover, we quantitatively analyzed the evolutionary changes by using simple mathematical models, which evaluated the evolution as an increase in the half-maximal inhibitory concentration (IC₅₀) and estimated quantitative characteristics of the evolutionary process. Our results clearly demonstrate not only the potential of a model cyanobacterium to adapt to a biochemically rich environment without a significant decrease in photosynthetic function but also the properties of its evolutionary process, which sheds light of the evolution of chloroplasts at the initial stage.     

Synthesis and Biological Action of a New Cyclic AMP Analogue

Abstract

A new cyclic AMP analogue, adenosine- 3′, 5′-cyclic methyl phosphonate (cAMP-Me) was chemically synthesized. This compound was not a substrate for phosphodiesterase, and it did not activate cAMP-dependent protein kinases (type I or type II). However, it inhibited cAMP phosphodiesterase and protein kinase at milimolar concentration levels. It also inhibited malignant cell proliferation in vitro.     

A peculiar new species in the genus Landouria Godwin-Austen, 1918 from China (Gastropoda: Heterobranchia: Stylommatophora: Camaenidae)

Landouria omphalostoma n. sp. is described from northern Yunnan, China. The new species is placed in the genus Landouria Godwin-Austen, 1918 based on the presence of tuberculated flagellum and swollen basal part in the bursa copulatrix, and on the absence of dart sacs and mucous glands. L. omphalostoma n. sp. is characterized by a horizontal aperture of the shell which is unique in the genus. This feature resembles those of only two other camaenid/bradybaenid taxa, species of the Chinese genus Pseudaspasita Möllendorff, 1902 and species of the Japanese genus Coelorus Pilsbry, 1900. This is the first verified record of the genus in China and the easternmost record of Landouria. This paper provides the taxonomic ground work for further studies of the repeated evolution of a horizontal aperture.     

Canopy‐scale relationships between stomatal conductance and photosynthesis in irrigated rice

Modeling stomatal behavior is critical in research on land–atmosphere interactions and climate change. The most common model uses an existing relationship between photosynthesis and stomatal conductance. However, its parameters have been determined using infrequent and leaf‐scale gas‐exchange measurements and may not be representative of the whole canopy in time and space. In this study, we used a top‐down approach based on a double‐source canopy model and eddy flux measurements throughout the growing season. Using this approach, we quantified the canopy‐scale relationship between gross photosynthesis and stomatal conductance for 3 years and their relationships with leaf nitrogen content throughout each growing season above a paddy rice canopy in Japan. The canopy‐averaged stomatal conductance (g_sc) increased with increasing gross photosynthesis per unit green leaf area (A_g), as was the case with leaf‐scale measurements, and 41–90% of its variation was explained by variations in A_g adjusted to account for the leaf‐to‐air vapor‐pressure deficit and CO₂ concentration using the Leuning model. The slope (m) in this model (g_sc versus the adjusted A_g) was almost constant within a 15‐day period, but changed seasonally. The m values determined using an ensemble dataset for two mid‐growing‐season 15‐day periods were 30.8 (SE = 0.5), 29.9 (SE = 0.7), and 29.9 (SE = 0.6) in 2004, 2005, and 2006, respectively; the overall mid‐season value was 30.3 and did not greatly differ among the 3 years. However, m appeared to be higher during the early and late growing seasons. The ontogenic changes in leaf nitrogen content strongly affected A_g and thus g_sc. In addition, we have discussed the agronomic impacts of the interactions between leaf nitrogen content and g_sc. Despite limitations in the observations and modeling, our canopy‐scale results emphasize the importance of continuous, season‐long estimates of stomatal model parameters for crops using top‐down approaches.     

Successful Treatment of Breakthrough Trichosporon asahii Fungemia by the Combination Therapy of Fluconazole and Liposomal Amphotericin B in a Patient with Follicular Lymphoma

Mycopathologia - Invasive trichosporonosis is a rare and lethal fungal infection that occurs in immunocompromised patients. Breakthrough trichosporonosis can occur in patients treated with...     

Tet1 regulates epigenetic remodeling of the pericentromeric heterochromatin and chromocenter organization in DNA hypomethylated cells

Pericentromeric heterochromatin (PCH), the constitutive heterochromatin of pericentromeric regions, plays crucial roles in various cellular events, such as cell division and DNA replication. PCH forms chromocenters in the interphase nucleus, and chromocenters cluster at the prophase of meiosis. Chromocenter clustering has been reported to be critical for the appropriate progression of meiosis. However, the molecular mechanisms underlying chromocenter clustering remain elusive. In this study, we found that global DNA hypomethylation, 5hmC enrichment in PCH, and chromocenter clustering of Dnmt1-KO ESCs were similar to those of the female meiotic germ cells. Tet1 is essential for the deposition of 5hmC and facultative histone marks of H3K27me3 and H2AK119ub at PCH, as well as chromocenter clustering. RING1B, one of the core components of PRC1, is recruited to PCH by TET1, and PRC1 plays a critical role in chromocenter clustering. In addition, the rearrangement of the chromocenter under DNA hypomethylated condition was mediated by liquid-liquid phase separation. Thus, we demonstrated a novel role of Tet1 in chromocenter rearrangement in DNA hypomethylated cells.     

15-Deoxy-Δ(12,14)-prostaglandin J(2) interferes inducible synthesis of prostaglandins E(2) and F(2α) that suppress subsequent adipogenesis program in cultured preadipocytes

Cultured preadipocytes enhance the synthesis of prostaglandin (PG) E(2) and PGF(2α) involving the induction of cyclooxygenase (COX)-2 during the growth phase upon stimulation with a mixture of phorbol 12-myristate 13-acetate, a mitogenic factor, and calcium ionophore A23187. Here, we studied the interactive effect of 15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)) on the inducible synthesis of the endogenous PGs in cultured preadipocytes and its implication in adipogenesis program. 15d-PGJ(2) interfered significantly the endogenous synthesis of those PGs in response to cell stimuli by suppressing the induction of COX-2 following the attenuation of NF-κB activation. In contrast, Δ(12)-PGJ(2) and troglitazone had almost no inhibitory effects, indicating a mechanism independent of the activation of peroxisome proliferator-activated receptor γ for the action of 15-PGJ(2). Pyrrolidinedithiocarbamate (PDTC), an NF-κB inhibitor, effectively inhibited on the inducible synthesis of those PGs in preadipocytes. Endogenous PGs generated by preadipocytes only during the growth phase in response to the cell stimuli autonomously attenuated the subsequent adipogenesis program leading to the differentiation and maturation of adipocytes. These effects were prevented by additional co-incubation of preadipocytes with either 15d-PGJ(2) or PDTC although 15d-PGJ(2) alone has no stimulatory effect. Moreover, 15d-PGJ(2) did not block the inhibitory effects of exogenous PGE(2) and PGF(2α) on the adipogenesis program in preadipocytes. Taken together, 15d-PGJ(2) can interfere the COX pathway leading to the induced synthesis of endogenous PGs that contribute to negative regulation of adipogenesis program in preadipocytes.     

Composition of aquatic invertebrates associated with macrophytes in Lake Tonle Sap,Cambodia

Faunal composition of aquatic invertebrate communities associated with submerged parts of several species of macrophytes were studied in different areas in littoral Lake Tonle Sap in Cambodia, with special reference to those in root systems (interrhizon) of a free-floating water hyacinth (Eichhornia crassipes). Nine phyla of invertebrates were collected, of which oligochaetes, shrimps and Limnoperna mussels were abundant along with meiobenthic crustaceans. The macrophyte-associated invertebrates in Lake Tonle Sap might be unique in having abundant sessile animals, such as sponges, bryozoans and Limnoperna mussels. The Limnoperna mussels attached to macrophytes were more abundant in offshore and inundated forest than in secluded vegetational stands toward the shoreline. It suggests that water movement can be an important factor determining the distribution and abundance of the sessile animals by controlling larval dispersions and might be associated with the hydrological characteristic of the lake, i.e., the lake opens to the large Mekong River with drastic seasonal changes in water level.     

Abnormal networks of immune response-related molecules in bone marrow cells from patients with rheumatoid arthritis as revealed by DNA microarray analysis

Introduction  

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic synovitis that progresses to destruction of cartilage and bone. Bone marrow (BM) cells have been shown to contribute to this pathogenesis. In this study, we compared differentially expressed molecules in BM cells from RA and osteoarthritis (OA) patients and analyzed abnormal regulatory networks to identify the role of BM cells in RA.