To secure phosphorus (P) from soil, most land plants use a direct phosphate uptake pathway via root hairs and epidermis and an indirect phosphate uptake pathway via mycorrhizal symbiosis. The ...interaction between these two pathways is unclear. Here, we mapped a network between transcription factors and mycorrhizal symbiosis-related genes using Y1H. Intriguingly, this gene regulatory network is governed by the conserved P-sensing pathway, centered on phosphate starvation response (PHR) transcription factors. PHRs are required for mycorrhizal symbiosis and regulate symbiosis-related genes via the P1BS motif. SPX-domain proteins suppress OsPHR2-mediated induction of symbiosis-related genes and inhibit mycorrhizal infection. In contrast, plants overexpressing OsPHR2 show improved mycorrhizal infection and are partially resistant to P-mediated inhibition of symbiosis. Functional analyses of network nodes revealed co-regulation of hormonal signaling and mycorrhizal symbiosis. This network deciphers extensive regulation of mycorrhizal symbiosis by endogenous and exogenous signals and highlights co-option of the P-sensing pathway for mycorrhizal symbiosis.
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•A new map of the rice mycorrhizal symbiosis transcriptional regulatory network•PHR-centered network controls arbuscular mycorrhizal symbiosis•Phosphate regulates mycorrhizal symbiosis via the SPX-PHR-centered network•Co-option of the conserved P-sensing pathway for mycorrhizal symbiosis
An interconnected network of 266 transcription factors and promoters of 47 mycorrhiza-related genes highlights a PHR-centered arbuscular mycorrhizal symbiosis transcriptional regulatory network in rice, which connects the indirect mycorrhizal phosphate uptake pathway with the direct phosphate uptake pathway.
Plants encounter various microbes in nature and must respond appropriately to symbiotic or pathogenic ones. In rice, the receptor-like kinase OsCERK1 is involved in recognizing both symbiotic and ...immune signals. However, how these opposing signals are discerned via OsCERK1 remains unknown. Here, we found that receptor competition enables the discrimination of symbiosis and immunity signals in rice. On the one hand, the symbiotic receptor OsMYR1 and its short-length chitooligosaccharide ligand inhibit complex formation between OsCERK1 and OsCEBiP and suppress OsCERK1 phosphorylating the downstream substrate OsGEF1, which reduces the sensitivity of rice to microbe-associated molecular patterns. Indeed, OsMYR1 overexpression lines are more susceptible to the fungal pathogen
, whereas
mutants show higher resistance. On the other hand, OsCEBiP can bind OsCERK1 and thus block OsMYR1-OsCERK1 heteromer formation. Consistently, the
mutant displayed a higher rate of mycorrhizal colonization at early stages of infection. Our results indicate that OsMYR1 and OsCEBiP receptors compete for OsCERK1 to determine the outcome of symbiosis and immunity signals.
Plant roots associate with diverse microbes (including bacteria, fungi, archaea, protists, and viruses) collectively called the root-associated microbiome. Among them, mycorrhizal fungi colonize host ...roots and improve their access to nutrients, usually phosphorus and nitrogen. In exchange, plants deliver photosynthetic carbon to the colonizing fungi. This nutrient exchange affects key soil processes, the carbon cycle, and plant health and therefore has a strong influence on the plant and microbe ecosystems. The framework of nutrient exchange and regulation between host plant and arbuscular mycorrhizal fungi has recently been established. The local and systemic regulation of mycorrhizal symbiosis by plant nutrient status and the autoregulation of mycorrhizae are strategies by which plants maintain a stabilizing free-market symbiosis. A better understanding of the synergistic effects between mycorrhizal fungi and mycorrhizosphere microorganisms is an essential precondition for their use as biofertilizers and bioprotectors for sustainable agriculture and forestry management.
The one-pot dehydration/hydrolysis of mono- and disaccharides to 5-hydroxymethylfurfural (HMF) in the presence of several imidazolium ionic liquids was efficiently performed. The study aims to make a ...mechanistic insights on the direct transformation of sugars to HMF, including glucose, fructose, galactose, sucrose, maltose and lactose. With the catalyst of NMPHSO
4
, a HMF yield of 87 % was achieved from sucrose. In addition, AMIMCl revealed a remarkable catalytic activity for the transformation of fructose to HMF without other catalyst or co-solvent and the yield of HMF was 91.1 %. Theoretical calculation results showed that AMIMCl expressed a more efficient catalytic activity than BMIMCl.
Graphical Abstract
Fructose could directly convert into HMF in AMIMCl without catalyst. Behaviors of disaccharides are largely determined by their basic units. The mechanism to explain the activity of AMIMCl has been confirmed by using DFT method.
The production of 5-hydroxymethylfurfural (HMF) from carbohydrates has been reported intensively in recent years. HMF is believed to be a versatile platform chemical and the focus of synthesizing it ...has especially been on the development of efficient catalysts, such as Lewis and Brønsted Acids. On the contrary, herein, we report a novel catalytic system that consists of 1-allyl-3-methylimidazolium chloride (AMIMCl) and N,N-Dimethylformamide (DMF) without any additional metal salts or acids, which leads to reasonable HMF yields (84.9%) and selectivities. In addition, the degradation mechanism of fructose catalyzed by AMIMCl is also proposed in this communication.
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•Simple and efficient ionic liquid/DMF binary reaction media is used.•A high yield (84%) of HMF is obtained from fructose.•Investigation of recovery method for HMF from media•AMIMCl played an important role in the fructose conversion mechanism.
Most land plants form symbiotic associations with arbuscular mycorrhizal (AM) fungi. These are the most common and widespread terrestrial plant symbioses, which have a global impact on plant mineral ...nutrition. The establishment of AM symbiosis involves recognition of the two partners and bidirectional transport of different mineral and carbon nutrients through the symbiotic interfaces within the host root cells. Intriguingly, recent discoveries have highlighted that lipids are transferred from the plant host to AM fungus as a major carbon source. In this review, we discuss the transporter-mediated transfer of carbon, nitrogen, phosphate, potassium and sulfate, and present hypotheses pertaining to the potential regulatory mechanisms of nutrient exchange in AM symbiosis. Current challenges and future perspectives on AM symbiosis research are also discussed.
This review summarizes transporter-mediated transfer of carbon (especially lipids) and mineral nutrients between arbuscular mycorrhizal fungi and their plant hosts and presents hypotheses pertaining to the potential regulatory mechanisms of nutrient exchange during AM symbiosis. Current challenges and future perspectives on AM symbiosis research are also discussed.
Summary
Most land plants associate with arbuscular mycorrhizal (AM) fungi to secure mineral nutrient acquisition, especially that of phosphorus. A phosphate starvation response (PHR)‐centered network ...regulates AM symbiosis.
Here, we identified 520 direct target genes for the rice transcription factor OsPHR1/2/3 during AM symbiosis using transcriptome deep sequencing and DNA affinity purification sequencing. These genes were involved in strigolactone biosynthesis, transcriptional reprogramming, and bidirectional nutrient exchange.
Moreover, we identified the receptor‐like kinase, Arbuscule Development Kinase 1 (OsADK1), as a new target of OsPHR1/2/3. Electrophoretic mobility shift assays and transactivation assays showed that OsPHR2 can bind directly to the P1BS elements within the OsADK1 promoter to activate its transcription. OsADK1 appeared to be required for mycorrhizal colonization and arbuscule development. In addition, hydroponic experiments suggested that OsADK1 may be involved in plant Pi starvation responses.
Our findings validate a role for OsPHR1/2/3 as master regulators of mycorrhizal‐related genes involved in various stages of symbiosis, and uncover a new RLK involved in AM symbiosis and plant Pi starvation responses.
Legumes, unlike other plants, have the ability to establish symbiosis with nitrogen-fixing rhizobia. It has been theorized that a unique property of legume root cortical cells enabled the initial ...establishment of rhizobial symbiosis
. Here we show that a SHORTROOT-SCARECROW (SHR-SCR) stem cell program in cortical cells of the legume Medicago truncatula specifies their distinct fate. Regulatory elements drive the cortical expression of SCR, and stele-expressed SHR protein accumulates in cortical cells of M. truncatula but not Arabidopsis thaliana. The cortical SHR-SCR network is conserved across legume species, responds to rhizobial signals, and initiates legume-specific cortical cell division for de novo nodule organogenesis and accommodation of rhizobia. Ectopic activation of SHR and SCR in legumes is sufficient to induce root cortical cell division. Our work suggests that acquisition of the cortical SHR-SCR module enabled cell division coupled to rhizobial infection in legumes. We propose that this event was central to the evolution of rhizobial endosymbiosis.
The direct transformation of cellulose and carbohydrates into 5-(hydroxymethyl)furfural (HMF) in the solvent BMIMCl using dual-core sulfonic acid ionic liquids (ILs) as catalysts and metal salts as ...co-catalysts was investigated, aiming at a more environmentally friendly process not involving chromium. From the high throughput screening of various metal salts, a combination of bi-C sub(3)SO sub(3)HMIMCH sub(3)SO sub(3) (IL-2) and manganese chloride (MnCl sub(2)) was found to be the most effective catalyst. HMF was directly afforded from cellulose in 66.5% yield. Thus, synthesis of HMF was successfully performed from cellulose using ILs and MnCl sub(2). Following the principles of green engineering, we recycled the catalyst in our system for cellulose hydrolysis and this catalyst maintained its good performance even after four runs. Furthermore, various sugars and lignocellulosic raw materials could be directly converted into HMF in reasonable yields under these conditions. The mechanism that explains the high activity of ILs in combination with MnCl sub(2) is also proposed.
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