RESUMO
Phosphorus (P) is an important nutrient for the growth and metabolism of algae. Although P typically limits the growth of algae, little is known regarding the molecular response of Microcystis aeruginosa under P starvation. The transcriptomic and physiological responses of Microcystis aeruginosa to P starvation were investigated in this study. P starvation affected the growth, photosynthesis, and Microcystin (MC) production of Microcystis aeruginosa and triggered cellular P-stress responses for 7 days. In terms of physiology, P starvation inhibited the growth and MC production, while the slight promotion of photosynthesis in Microcystis aeruginosa compared to P-replete. For transcriptome, the down-regulation of genes related to MC production controlled by mcy genes and ribosome metabolism (17 genes encoding ribosomal proteins) was observed while transport genes (sphX and pstSAC) were significantly upregulated. In addition, some other genes are related to photosynthesis and the use of other forms of P displayed increases or decreases in transcripts abundance. These results suggested that the limitation of P had a diverse performance on aspects of growth and metabolism in M. aeruginosa and obviously enhanced the ability to adapt to the P stress environment. They provide a comprehensive understanding of the P physiology of Microcystis aeruginosa and theoretical support for eutrophication.
Assuntos
Microcystis , Transcriptoma , Microcistinas/metabolismo , Pseudomonas aeruginosa/metabolismo , Fósforo/metabolismo , Perfilação da Expressão GênicaRESUMO
Increased root secretion of H+ is a known strategy in plant adaption to low phosphorus (P) stress as it enhances mobilization of sparingly soluble P sources in the soil. However, our knowledge of the full effects induced by this enhanced acidification of the rhizosphere remains incomplete. In this study we found that P deficiency increased the net H+ flux rate from soybean (Glycine max) roots. Among the eight H+-pyrophosphatase (GmVP) genes in the soybean genome, GmVP2 showed the highest expression level under low P conditions. Transient expression of a GmVP2-GFP construct in tobacco (Nicotiana tabacum) leaves, together with functional characterization of GmVP2 in transgenic soybean hairy roots demonstrated that it encodes a plasma-membrane transporter that mediates H+ exudation. Overexpression of GmVP2 in Arabidopsis resulted in enhanced root H+ exudation, promoted root growth, and improved the utilization of sparingly soluble Ca-P. The improved root growth caused by GmVP2-overexpression might be due to the differential expression of genes related to hormone and flavonoid metabolism, and to root development. Overexpression of GmVP2 also changed the structure of the rhizospheric microbial community, as reflected by a preferential accumulation of Acidobacteria. Overall, our results suggest that GmVP2 mediates H+ exudation in the root response to Pi starvation, and that this influences plant growth, the mobilization sparingly soluble P-sources, and the structure of the microbial community in a coordinated manner.
Assuntos
Arabidopsis , Fósforo , Fósforo/metabolismo , Solo/química , Prótons , Rizosfera , Raízes de Plantas/metabolismo , Arabidopsis/fisiologiaRESUMO
BACKGROUND: Phosphorus (P) is an essential macronutrient for plant growth and development. Upon P shortage, plant responds with massive reprogramming of transcription, the Phosphate Starvation Response (PSR). In parallel, the production of strigolactones (SLs)-a class of plant hormones that regulates plant development and rhizosphere signaling molecules-increases. It is unclear, however, what the functional link is between these two processes. In this study, using tomato as a model, RNAseq was used to evaluate the time-resolved changes in gene expression in the roots upon P starvation and, using a tomato CAROTENOID CLEAVAGE DIOXYGENASES 8 (CCD8) RNAi line, what the role of SLs is in this. RESULTS: Gene ontology (GO)-term enrichment and KEGG analysis of the genes regulated by P starvation and P replenishment revealed that metabolism is an important component of the P starvation response that is aimed at P homeostasis, with large changes occurring in glyco-and galactolipid and carbohydrate metabolism, biosynthesis of secondary metabolites, including terpenoids and polyketides, glycan biosynthesis and metabolism, and amino acid metabolism. In the CCD8 RNAi line about 96% of the PSR genes was less affected than in wild-type (WT) tomato. For example, phospholipid biosynthesis was suppressed by P starvation, while the degradation of phospholipids and biosynthesis of substitute lipids such as sulfolipids and galactolipids were induced by P starvation. Around two thirds of the corresponding transcriptional changes depend on the presence of SLs. Other biosynthesis pathways are also reprogrammed under P starvation, such as phenylpropanoid and carotenoid biosynthesis, pantothenate and CoA, lysine and alkaloids, and this also partially depends on SLs. Additionally, some plant hormone biosynthetic pathways were affected by P starvation and also here, SLs are required for many of the changes (more than two thirds for Gibberellins and around one third for Abscisic acid) in the gene expression. CONCLUSIONS: Our analysis shows that SLs are not just the end product of the PSR in plants (the signals secreted by plants into the rhizosphere), but also play a major role in the regulation of the PSR (as plant hormone).
Assuntos
Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Compostos Heterocíclicos com 3 Anéis/metabolismo , Lactonas/metabolismo , Fósforo/deficiência , Fósforo/metabolismo , Raízes de Plantas/metabolismo , Solanum lycopersicum/genética , Solanum lycopersicum/metabolismo , Produtos Agrícolas/genética , Produtos Agrícolas/metabolismo , Variação Genética , Genótipo , Raízes de Plantas/genética , Fatores de Transcrição/metabolismoRESUMO
Embothrium coccineum produces cluster roots (CR) to acquire sparingly soluble phosphorus (P) from the soil through the exudation of organic compounds. However, the physiological mechanisms involved in carbon drainage through its roots, as well as the gene expression involved in the biosynthesis of carboxylates and P uptake, have not been explored. In this work, we evaluated the relationship between carboxylate exudation rate and phosphoenolpyruvate carboxylase (PEPC) activity in roots of E. coccineum seedlings grown in a nutrient-poor volcanic substrate. Second, we evaluated CR formation and the expression of genes involved in the production of carboxylates (PEPC) and P uptake (PHT1) in E. coccineum seedlings grown under three different P supplies in hydroponic conditions. Our results showed that the carboxylate exudation rate was higher in CR than in non-CR, which was consistent with the higher PEPC activity in CR. We found higher CR formation in seedlings grown at 5 µM of P supply, concomitant with a higher expression of EcPEPC and EcPHT1 in CR than in non-CR. Overall, mature CR of E. coccineum seedlings growing on volcanic substrates poor in nutrients modify their metabolism compared to non-CR, enhancing carboxylate biosynthesis and subsequent carboxylate exudation. Additionally, transcriptional responses of EcPEPC and EcPHT1 were induced simultaneously when E. coccineum seedlings were grown in P-limited conditions that favored CR formation. Our results showed, for the first time, changes at the molecular level in CR of a species of the Proteaceae family, demonstrating that these root structures are highly specialized in P mobilization and uptake.
Assuntos
Fósforo , Proteaceae , Expressão Gênica , Raízes de Plantas , SoloRESUMO
Phosphorus is an essential nutrient required for soybean growth but is bound in phytic acid which causes negative effects on both the environment as well as the animal nutrition. Lowering of phytic acid levels is associated with reduced agronomic characteristics, and relatively little information is available on the response of soybean plants to phosphorus (P) starvation. In this study, we evaluated the effects of different P starvation concentrations on the phytic acid content, growth, and yield of seven mutant genotypes along with the unirradiated control, JS-335, in a hydroponics growth system. The low phytic acid containing mutant genotypes, IR-JS-101, IR-DS-118, and IR-V-101, showed a relatively high growth rate in low P concentration containing nutrient solution (2 µM), whereas the high P concentration (50 µM) favored the growth of IR-DS-111 and IR-DS-115 mutant genotypes containing moderate phytate levels. The mutant genotypes with high phytic acid content, IR-DS-122, IR-DS-114, and JS-335, responded well under P starvation and did not have any significant effect on the growth and yield of plants. Moreover, the reduction of P concentration in nutrient solution from 50 to 2 µM also reduced the phytic acid content in the seeds of all the soybean genotypes under study. The desirable agronomic performance of low phytic acid containing mutant genotype IR-DS-118 reported in this study suggested it to be a P-efficient genotype which could be considered for agricultural practices under P limiting soils.