The active Fe chelator proline-2'-deoxymugineic acid enhances peanut yield by improving soil Fe availability and plant Fe status

From intercropping to monocropping: The effects of Pseudomonas strain to facilitate nutrient efficiency in peanut and soil

As an oilseed crop, the yield and quality of peanuts are severely constrained by nutrient deficiencies, particularly in calcareous soils in northern China. Maize-peanut intercropping is an effective strategy to enhance mineral nutrient efficiency in peanuts via plant-microbe interaction, but the underlying mechanisms remain elusive. Here, we conducted experiments using a Pseudomonas strain (Pse.IP6) with diverse beneficial characteristics, which was isolated from the rhizosphere of intercropped peanuts. Additionally, Pse.IP6 exhibits high phylogenetic similarity with the Amplicon Sequence Variants 48 (ASV48) which belongs to Pseudomonas and is positively correlated with Fe in plants and soil in intercropping. To confirm the plant growth-promoting potential of Pse.IP6 and its role in intercropping advantage, we constructed pot experiments. Results revealed that Pse.IP6 promoted shoot growth and root development, as well significantly enhanced SPAD value, net photosynthetic rate, stomatal conductance, and transpiration rate of peanut leaves. Moreover, the application of Pse.IP6 resulted in a notable accumulation of nitrogen (N), phosphorus (P), and potassium (K) in shoot and active iron (Fe) in leaves, accompanied by an increased K-N ratio. The primary reason for the nutrient promotion is the enhancement of the bioavailability of nitrate, ammonium, P, K, and Fe in the rhizosphere. Collectively, our findings demonstrate that Pse.IP6, enriched in intercropping peanut, is a plant growth-promoting bacteria, represented by transferring the intercropping advantage on nutrients activation to monocropping peanuts. Our results offer insights into plant-rhizobacteria interaction mechanisms and therefore provide a rhizobacteria-based pathway to improve nutrient efficiency and productivity of crops.

Molecular-based characterization and bioengineering of Sorghum bicolor to enhance iron deficiency tolerance in iron-limiting calcareous soils

Plant biomass can significantly contribute to alternative energy sources. Sorghum bicolor is a promising plant for producing energy, but is susceptible to iron deficiency, which inhibits its cultivation in iron-limiting calcareous soils. The molecular basis for the susceptibility of sorghum to iron deficiency remains unclear. Here, we explored the sorghum genome to identify genes involved in iron uptake and translocation. Iron deficiency-responsive gene expression was comparable to that in other graminaceous plants. A nicotianamine synthase gene, SbNAS1, was induced in response to iron deficiency, and SbNAS1 showed enzyme activity. Sorghum secreted 2'-deoxymugineic acid and other phytosiderophores under iron deficiency, but their levels were relatively low. Intercropping of sorghum with barley or rice rescued iron deficiency symptoms of sorghum. To produce bioengineered sorghum with enhanced tolerance to iron deficiency, we introduced four cassettes into sorghum: 35S promoter-OsIRO2 for activation of iron acquisition-related gene expression, SbIRT1 promoter-Refre1/372 for enhanced ferric-chelate reductase activity, and barley IDS3, and HvNAS1 genomic fragments for enhanced production of phytosiderophores and nicotianamine. The resultant single sorghum line exhibited enhanced secretion of phytosiderophores, increased ferric-chelate reductase activity, and improved iron uptake and leaf greenness compared with non-transformants under iron-limiting conditions. Similar traits were also conferred to rice by introducing the four cassettes. Moreover, these rice lines showed similar or better tolerance in calcareous soils and increased grain iron accumulation compared with previous rice lines carrying two or three comparable cassettes. These results provide a molecular basis for the bioengineering of sorghum tolerant of low iron availability in calcareous soils.

Integrated physiological, transcriptomic and metabolomic analyses reveal the mechanism of peanut kernel weight reduction under waterlogging stress

Waterlogging stress (WS) hinders kernel development and directly reduces peanut yield; however, the mechanism of kernel filling in response to WS remains unknown. The waterlogging-sensitive variety Huayu 39 was subjected to WS for 3 days at 7 days after the gynophores touched the ground (DAG). We found that WS affected kernel filling at 14, 21, and 28 DAG. WS decreased the average filling rate and kernel dry weight, while transcriptome sequencing and widely targeted metabolomic analysis revealed that WS inhibited the gene expression in starch and sucrose metabolism, which reduced sucrose input and transformation ability. Additionally, genes related to ethylene and melatonin synthesis and the accumulation of tryptophan and methionine were upregulated in response to WS. WS upregulated the expression of the gene encoding tryptophan decarboxylase (AhTDC), and overexpression of AhTDC in Arabidopsis significantly reduced the seed length, width, and weight. Therefore, WS reduced the kernel-filling rate, leading to a reduction in the 100-kernel weight. This survey informs the development of measures that alleviate the negative impact of WS on peanut yield and quality and provides a basis for exploring high-yield and high-quality cultivation, molecular-assisted breeding, and waterlogging prevention in peanut farming.

Deciphering the regulation of transporters and mitogen-activated protein kinase in arsenic and iron exposed rice

This study investigates the influence of arsenic (As) and iron (Fe) on the molecular aspects of rice plants. The mRNA-abundance of As (OsLsi, OsPHT, OsNRAMP1, OsABCC1) and Fe (OsIRT, OsNRAMP1, OsYSL, OsFRDL1, OsVIT2, OsSAMS1, OsNAS, OsNAAT1, OsDMAS1, OsTOM1, OsFER) related genes has been observed in 12-d old As and Fe impacted rice varieties. Analyses of phytosiderophores synthesis and Fe-uptake genes affirm the existence of specialized Fe-uptake strategies in rice with varieties PB-1 and Varsha favouring strategy I and II, respectively. Expression of OsNAS3, OsVIT2, OsFER and OsABCC1 indicated PB-1's tolerance towards Fe and As. Analysis of mitogen-activated protein kinase cascade members (OsMKK3, OsMKK4, OsMKK6, OsMPK3, OsMPK4, OsMPK7, and OsMPK14) revealed their importance in the fine adjustment of As/Fe in the rice system. A conditional network map was generated based on the gene expression pattern that unfolded the differential dynamics of both rice varieties. The mating based split ubiquitin system determined the interaction of OsIRT1 with OsMPK3, and OsLsi1 with both OsMPK3 and OsMPK4. In-silico tools also confirmed the binding affinities of OsARM1 with OsLsi1, OsMPK3 and OsMPK4, and of OsIDEF1/OsIRO2 with OsIRT1 and OsMPK3, supporting our hypothesis that OsARM1, OsIDEF1, OsIRO2 were active in the connections discovered by mbSUS.