Downregulation of GeBP-like α factor by MiR827 suggests their involvement in senescence and phosphate homeostasis

Background Leaf senescence is a genetically controlled degenerative process intimately linked to phosphate homeostasis during plant development and responses to environmental conditions. Senescence is accelerated by phosphate deficiency, with recycling and mobilization of phosphate from senescing leaves serving as a major phosphate source for sink tissues. Previously, miR827 was shown to play a significant role in regulating phosphate homeostasis, and induction of its expression was also observed during Arabidopsis leaf senescence. However, whether shared mechanisms underlie potentially common regulatory roles of miR827 in both processes is not understood. Here, we dissect the regulatory machinery downstream of miR827. Results Overexpression or inhibited expression of miR827 led to an acceleration or delay in the progress of senescence, respectively. The transcriptional regulator GLABRA1 enhancer-binding protein (GeBP)-like (GPLα) gene was identified as a possible target of miR827. GPLα expression was elevated in miR827-suppressed lines and reduced in miR827-overexpressing lines. Furthermore, heterologous co-expression of pre-miR827 in tobacco leaves reduced GPLα transcript levels, but this effect was eliminated when pre-miR827 recognition sites in GPLα were mutated. GPLα expression is induced during senescence and its inhibition or overexpression resulted in senescence acceleration and inhibition, accordingly. Furthermore, GPLα expression was induced by phosphate deficiency, and overexpression of GPLα led to reduced expression of phosphate transporter 1 genes, lower leaf phosphate content, and related root morphology. The encoded GPLα protein was localized to the nucleus. Conclusions We suggest that MiR827 and the transcription factor GPLα may be functionally involved in senescence and phosphate homeostasis, revealing a potential new role for miR827 and the function of the previously unstudied GPLα. The close interactions between senescence and phosphate homeostasis are further emphasized by the functional involvement of the two regulatory components, miR827 and GPLα, in both processes and the interactions between them.

Isolation and Characterization of Phosphate Solubilizing Streptomyces Endemic From Sugar Beet Fields Of the Beni-Mellal Region In Morocco

In this research, we isolated and characterized Streptomyces strains, endemic from sugar beet fields of the Beni-Mellal region, able to use natural rock phosphate (RP) and tricalcium phosphate (TCP), as sole phosphate source. Ten Streptomyces isolates yielded a comparable biomass in the presence of these two insoluble phosphate sources, indicating that they were able to extract similar amount of phosphorus (P) from the latter for their own growth. Interestingly, five strains released soluble P in large excess from TCP in their culture broth whereas only two strains, BP, related to Streptomyces bellus and BYC, related to Streptomyces enissocaesilis, released a higher or similar amount of soluble P from RP than from TCP, respectively. This indicated that the rate of P released from these insoluble phosphate sources exceeded its consumption rate for bacterial growth and that most strains solubilized TCP more efficiently than RP. Preliminary results suggested that the solubilization process of BYC, the most efficient RP and TCP solubilizing strain, involves both acidification of the medium and excretion of siderophores. Actinomycete strains possessing such interesting RP solubilizing abilities may constitute a novel kind of intrans beneficial for plant nutrition and more environmentally friendly than chemical fertilizers in current use.

Synthesis of Calcium Phosphate Extracted from Eggshell Waste through Precipitation Method

Biomaterials for bone engineering applications are eagerly developing as traditional bone grafting methods show several drawbacks after and during operation. Eggshell waste contains high calcium suitable for developing biomaterials in hard tissue engineering as bone made up of calcium and phosphate. The precipitation method is one of the synthesis methods to produce calcium phosphate (CaP). In this work, calcium source was extracted from eggshell waste while phosphate source was from ortho-phosphoric acid. The synthesized CaP powder was calcined at different temperatures. X-ray diffraction (XRD) analysis shows two types of CaP patterns are hydroxyapatite (HA) and β-Tricalcium phosphate (β-TCP). Fourier transform infrared (FTIR) shows phosphate ion band in every sample while scanning electron microscopy (SEM) shows the transformation of structure from needle-like to more fluffy and rounded-edge structure from uncalcined to 1000°C. From the results obtained, CaP extracted from eggshell waste was successfully synthesized from the precipitation method. This method contributes to the materials processing cost reduction and increases the application of natural materials instead of synthetic ones.

Concurrent occurrence of electrochemical dissolution/deposition of cobalt–calcium phosphate composite

Solid phase of phosphate source (hydroxyapatite) is utilized for the electrochemical preparation of cobalt–calcium phosphate composite (CCPC) film.

Medium optimization for exopolysaccharides production by Bacillus Zhangzhouensis BZ 16 strain isolated from Khnifiss Lagoon

The increased demand for natural polymers for diverse industrial applications in last years has led to a renovated interest in exopolysaccharides (EPS) production by microorganisms. Ecological roles of EPS especially for those isolated from extreme habitats such as hypersaline ponds have been reported in several studies. A moderate halophilic strain producing exopolysaccharide (EPS) has been isolated earlier. However, the EPS production of the strain (2 g/L) was relatively low to exploit it at the industrial level. In the present work, the strain was identified as Bacillus zhangzhouensis and named as BZ 16 and the optimal medium was studied to boost the EPS production. Maximum EPS production was obtained in medium with 125 g/L sucrose, 30 g/L yeast extract. Phosphate source inhibited EPS production even if it increased the growth. Under optimal medium composition, EPS was produced at 12.37 g/L, which was 6 times greater than the production yield achievable without optimizing conditions.

Isolation, identification and characterization of phosphate solubilizing bacteria in soils of coal mines landfills of Chhattisgarh

Phosphate solubilizing bacteria have the ability to solubilize the insoluble phosphates and to improve the quality of soil health and fertility. Efficacy of phosphate solubilizing microorganisms has been identified on the basis of kinetics and phosphorus accumulation. In this study, twenty eight soil samples were collected from different coal mines landfills of Chhattisgarh and occurrence of phosphate solubilizing bacteria (PSB) was isolated, purified and identified. In addition, the phosphate solubilizing capacity of bacteria based on the formation of visible or halo zone on Pikovskaya agar plates (PVK) and broth having tricalcium phosphate (TCP) and rock phosphate (RP) as a phosphate source was estimated at Dr. C.V. Raman University, Kota, Bilaspur (Chhattisgarh). The result revealed dominance of Pseudomonas syringae as major phosphate solubilizers, along with Bacillus subtillis followed by Pantoea dispersa, Bacillus circulans. Use of these PSB as bioinoculants increased the available P in soil to the extent of 194 and 246 µg/ml of P. the soluble P in case of rock phosphate was less than tricalcium phosphate. The maximum solubilization was observed after 15 days follow by a decrease in amount of soluble P.

Inorganic Phosphate Solubilization by Rhizosphere Bacterium Paenibacillus sonchi: Gene Expression and Physiological Functions

Due to the importance of phosphorus (P) in agriculture, crop inoculation with phosphate-solubilizing bacteria is a relevant subject of study. Paenibacillus sonchi genomovar Riograndensis SBR5 is a promising candidate for crop inoculation, as it can fix nitrogen and excrete ammonium at a remarkably high rate. However, its trait of phosphate solubilization (PS) has not yet been studied in detail. Here, differential gene expression and functional analyses were performed to characterize PS in this bacterium. SBR5 was cultivated with two distinct P sources: NaH2PO4 as soluble phosphate source (SPi) and hydroxyapatite as insoluble phosphate source (IPi). Total RNA of SBR5 cultivated in those two conditions was isolated and sequenced, and bacterial growth and product formation were monitored. In the IPi medium, the expression of 68 genes was upregulated, whereas 100 genes were downregulated. Among those, genes involved in carbon metabolism, including those coding for subunits of 2-oxoglutarate dehydrogenase, were identified. Quantitation of organic acids showed that the production of tricarboxylic acid cycle-derived organic acids was reduced in IPi condition, whereas acetate and gluconate were overproduced. Increased concentrations of proline, trehalose, and glycine betaine revealed active osmoprotection during growth in IPi. The cultivation with hydroxyapatite also caused the reduction in the motility of SBR5 cells as a response to Pi depletion at the beginning of its growth. SBR5 was able to solubilize hydroxyapatite, which suggests that this organism is a promising phosphate-solubilizing bacterium. Our findings are the initial step in the elucidation of the PS process in P. sonchi SBR5 and will be a valuable groundwork for further studies of this organism as a plant growth-promoting rhizobacterium.