Vitamin D status alters genes involved in ovarian steroidogenesis in muskrat granulosa cells.

This study aims to explore the relationship between altered vitamin D (VitD3) status and ovarian steroidogenesis in muskrats during the breeding and non-breeding seasons. During the breeding season, the ovaries of muskrats were observably enlarged and increased in weight, accompanied by elevated serum and ovarian VitD3 status. Vitamin D receptor (VDR), VitD3 metabolic molecules (CYP2R1, CYP27B1, and CYP24A1), and steroidogenic enzymes were immunolocalized in the ovarian cells of muskrats. The mRNA levels of VDR, CYP2R1, CYP27B1, and steroidogenic enzymes were considerably higher during the breeding season compared to the non-breeding season. RNA-seq analysis revealed a prominent enrichment of vitamin-related and ovarian steroidogenesis pathways. Furthermore, the addition of 1,25(OH)2D3 to the muskrat granulosa cells in vitro increased VDR and steroidogenic enzymes mRNA levels and enhanced the 17ß-estradiol level. Overall, these findings supported that VitD3 promotes the secretion of steroid hormones, thereby affecting seasonal changes in ovarian function in the muskrats.

EGFR-ERK1/2 signaling and mitochondrial dynamics in seasonal ovarian steroidogenesis of the muskrats (Ondatra zibethicus).

The dynamic systems of mitochondria, including mitochondrial fusion and fission, are essential for ovarian endocrine and follicular development. Meanwhile, ERK1/2 signaling is an important mechanism mediating altered mitochondrial dynamics and steroidogenesis. The purpose of this study was to investigate the seasonal changes in ovarian steroidogenesis concerning EGFR-ERK1/2 signaling and mitochondrial dynamics of the muskrats (Ondatra zibethicus). The results showed that follicular development in the muskrats remained in the tertiary follicular stage during the non-breeding season, accompanied by a significant decrease in serum and ovarian concentrations of 17ß-estradiol and progesterone from the breeding season to the non-breeding season. EGF, EGFR, ERK1/2, p-ERK1/2, and mitochondrial dynamics regulators were mainly localized in granulosa cells and theca cells of muskrats during the breeding and non-breeding seasons. The mRNA levels of Egfr, Erk1/2, Mfn1/2, Opa1, Drp1, and steroidogenic enzymes in the ovaries were remarkably higher during the breeding season. The 17ß-estradiol concentrations in the serum and ovaries as well as the relative levels of Mfn1/2, Opa1, and Drp1 were positively associated with each other. Furthermore, transcriptomic analysis of the ovaries revealed that differentially expressed genes might be linked to steroid biosynthesis, estrogen signaling pathway, and mitochondrial membrane-related pathways. In conclusion, these results suggest that the up-regulation of mitochondrial dynamics regulators during the breeding season is closely associated with enhanced ovarian steroidogenesis in the muskrats, which may be regulated by upstream EGFR-ERK1/2 signaling.

Isolation and Characterization of Phosphate Solubilizing Bacteria from Paddy Field Soils in Japan.

Phosphorus (P) is abundant in soil and is essential for plant growth and development; however, it is easily rendered insoluble in complexes of different types of phosphates, which may lead to P deficiency. Therefore, increases in the amount of P released from phosphate minerals using microbial inoculants is an important aspect of agriculture. The present study used inorganic phosphate solubilizing bacteria (iPSB) in paddy field soils to develop microbial inoculants. Soils planted with rice were collected from different regions of Japan. Soil P was sequentially fractionated using the Hedley method. iPSB were isolated using selective media supplemented with tricalcium phosphate (Ca-P), aluminum phosphate (Al-P), or iron phosphate (Fe-P). Representative isolates were selected based on the P solubilization index and soil sampling site. Identification was performed using 16S rRNA and rpoB gene sequencing. Effectiveness was screened based on rice cultivar Koshihikari growth supplemented with Ca-P, Al-P, or Fe-P as the sole P source. Despite the relatively homogenous soil pH of paddy field sources, three sets of iPSB were isolated, suggesting the influence of fertilizer management and soil types. Most isolates were categorized as ß-Proteobacteria (43%). To the best of our knowledge, this is the first study to describe the genera Pleomorphomonas, Rhodanobacter, and Trinickia as iPSB. Acidovorax sp. JC5, Pseudomonas sp. JC11, Burkholderia sp. JA6 and JA10, Sphingomonas sp. JA11, Mycolicibacterium sp. JF5, and Variovorax sp. JF6 promoted plant growth in rice supplemented with an insoluble P source. The iPSBs obtained may be developed as microbial inoculants for various soil types with different P fixation capacities.

Genetic Diversity and Characterization of Symbiotic Bacteria Isolated from Endemic Phaseolus Cultivars Located in Contrasting Agroecosystems in Venezuela.

Phaseolus vulgaris is a grain cultivated in vast areas of different countries. It is an excellent alternative to the other legumes in the Venezuelan diet and is of great agronomic interest due to its resistance to soil acidity, drought, and high temperatures. Phaseolus establishes symbiosis primarily with Rhizobium and Ensifer species in most countries, and this rhizobia-legume interaction has been studied in Asia, Africa, and the Americas. However, there is currently no evidence to show that rhizobia nodulate the endemic cultivars of P. vulgaris in Venezuela. Therefore, we herein investigated the phylogenetic diversity of plant growth-promoting and N2-fixing nodulating bacteria isolated from the root nodules of P. vulgaris cultivars in a different agroecosystem in Venezuela. In comparisons with other countries, higher diversity was found in isolates from P. vulgaris nodules, ranging from α- and ß-proteobacteria. Some isolates belonging to several new phylogenetic lineages within Bradyrhizobium, Ensifer, and Mesorhizobium species were also specifically isolated at some topographical regions. Additionally, some isolates exhibited tolerance to high temperature, acidity, alkaline pH, salinity stress, and high Al levels; some of these characteristics may be related to the origin of the isolates. Some isolates showed high tolerance to Al toxicity as well as strong plant growth-promoting and antifungal activities, thereby providing a promising agricultural resource for inoculating crops.

Characterization of Rhizobia for the Improvement of Soybean Cultivation at Cold Conditions in Central Europe.

In central Europe, soybean cultivation is gaining increasing importance to reduce protein imports from overseas and make cropping systems more sustainable. In the field, despite the inoculation of soybean with commercial rhizobia, its nodulation is low. In many parts of Europe, limited information is currently available on the genetic diversity of rhizobia and, thus, biological resources for selecting high nitrogen-fixing rhizobia are inadequate. These resources are urgently needed to improve soybean production in central Europe. The objective of the present study was to identify strains that have the potential to increase nitrogen fixation by and the yield of soybean in German soils. We isolated and characterized 77 soybean rhizobia from 18 different sampling sites. Based on a multilocus sequence analysis (MLSA), 71% of isolates were identified as Bradyrhizobium and 29% as Rhizobium. A comparative analysis of the nodD and nifH genes showed no significant differences, which indicated that the soybean rhizobia symbiotic genes in the present study belong to only one type. One isolate, GMF14 which was tolerant of a low temperature (4°C), exhibited higher nitrogen fixation in root nodules and a greater plant biomass than USDA 110 under cold conditions. These results strongly suggest that some indigenous rhizobia enhance biological nitrogen fixation and soybean yield due to their adaption to local conditions.

Burkholderia and Paraburkholderia are Predominant Soybean Rhizobial Genera in Venezuelan Soils in Different Climatic and Topographical Regions.

The climate, topography, fauna, and flora of Venezuela are highly diverse. However, limited information is currently available on the characterization of soybean rhizobia in Venezuela. To clarify the physiological and genetic diversities of soybean rhizobia in Venezuela, soybean root nodules were collected from 11 soil types located in different topographical regions. A total of 395 root nodules were collected and 120 isolates were obtained. All isolates were classified in terms of stress tolerance under different concentrations of NaCl and Al3+. The tolerance levels of isolates to NaCl and Al3+ varied. Based on sampling origins and stress tolerance levels, 44 isolates were selected for further characterization. An inoculation test indicated that all isolates showed the capacity for root nodulation on soybean. Based on multilocus sequence typing (MLST), 20 isolates were classified into the genera Rhizobium and Bradyrhizobium. The remaining 24 isolates were classified into the genus Burkholderia or Paraburkholderia. There is currently no evidence to demonstrate that the genera Burkholderia and Paraburkholderia are the predominant soybean rhizobia in agricultural fields. Of the 24 isolates classified in (Para) Burkholderia, the nodD-nodB intergenic spacer regions of 10 isolates and the nifH gene sequences of 17 isolates were closely related to the genera Rhizobium and Bradyrhizobium, respectively. The root nodulation numbers of five (Para) Burkholderia isolates were higher than those of the 20 α-rhizobia. Furthermore, among the 44 isolates tested, one Paraburkholderia isolate exhibited the highest nitrogen-fixation activity in root nodules.

Isolation and Screening of Indigenous Plant Growth-promoting Rhizobacteria from Different Rice Cultivars in Afghanistan Soils.

To develop biofertilizers for rice in Afghanistan, 98 plant growth-promoting rhizobacteria were isolated from rice plants and their morphological and physiological characteristics, such as indole-3-acetic acid production, acetylene reduction, phosphate and potassium solubilization, and siderophore production, were evaluated. The genetic diversity of these bacteria was also analyzed based on 16S rRNA gene sequences. Of 98 bacteria, 89.7% produced IAA, 54.0% exhibited nitrogenase activity, and 40% showed phosphate solubilization and siderophore production. Some isolates assigned to Pseudomonas (brassicacearum, chengduensis, plecoglossicida, resinovorans, and straminea) formed a relationship with rice, and P. resinovorans and P. straminea showed nitrogen fixation. Rhizobium borbori and R. rosettiformans showed a relationship with rice plants and nitrogen fixation. Among the isolates examined, AF134 and AF137 belonging to Enterobacter ludwigii and P. putida produced large amounts of IAA (92.3 µg mL-1) and exhibited high nitrogenase activity (647.4 nmol C2H4 h-1), respectively. In the plant growth test, more than 70% of the inoculated isolates showed significantly increased root and shoot dry weights. Highly diverse bacterial isolates showing promising rice growth-promoting traits were obtained from Afghanistan alkaline soils.