From Charge to Spin: An In-Depth Exploration of Electron Transfer in Energy Electrocatalysis.

Catalytic materials play crucial roles in various energy-related processes, ranging from large-scale chemical production to advancements in renewable energy technologies. Despite a century of dedicated research, major enduring challenges associated with enhancing catalyst efficiency and durability, particularly in green energy-related electrochemical reactions, remain. Focusing only on either the crystal structure or electronic structure of a catalyst is deemed insufficient to break the linear scaling relationship (LSR), which is the golden rule for the design of advanced catalysts. The discourse in this review intricately outlines the essence of heterogenous catalysis reactions by highlighting the vital roles played by electron properties. The physical and electrochemical properties of electron charge and spin that govern catalysis efficiencies are analyzed. Emphasis is placed on the pronounced influence of external fields in perturbing the LSR, underscoring the vital role that electron spin plays in advancing high-performance catalyst design. The review culminates by proffering insights into the potential applications of spin catalysis, concluding with a discussion of extant challenges and inherent limitations. This article is protected by copyright. All rights reserved.

Trichoderma guizhouense NJAU4742 augments morphophysiological responses, nutrient availability and photosynthetic efficacy of ornamental Ilex verticillata.

Winterberry holly (Ilex verticillata [L.] A. Gray), a deciduous shrub producing glossy bright red berries, is a valuable ornamental and medicinal plant with good market prospects. However, the growth and development of I. verticillata are significantly affected by various stresses, and environmentally hazardous agrochemicals are often used to mitigate them. Trichoderma spp., ubiquitous soil-borne eco-friendly plant growth-promoting fungi, are potent biostimulants and biofertilizers and viable alternatives to agrochemicals for healthy and sustainable agriculture. In this study, the temporal efficacy of different dosages of the filamentous fungus Trichoderma guizhouense NJAU4742 in promoting morphophysiological responses of I. verticillata and the physicochemical properties and enzymatic activities of the substrate were investigated. Different concentrations of the strain T. guizhouense NJAU4742 spore suspension (C [0%], T1 [5%, v/m], T2 [10%, v/m] and T3 [15%, v/m]) were injected in the substrate contained in a pot in which 1-year-old I. verticillata was planted for temporal treatment (15, 45 and 75 days) under open-air conditions. The beneficial effects of T2 and/or T3 treatment for a long duration (75 days) were evident on the different root, aerial and photosynthetic traits; total contents of nitrogen (N), phosphorus (P) and potassium (K) in different tissues and the physicochemical properties of the substrate and its enzymatic activities (urease and invertase). Overall, the study revealed the potency of strain T. guizhouense NJAU4742 as a sustainable solution to improve the growth and development and ornamental value of I. verticillata.

Phosphate Transporter OsPT4, Ubiquitinated by E3 Ligase OsAIRP2, Plays a Crucial Role in Phosphorus and Nitrogen Translocation and Consumption in Germinating Seed.

Phosphorus (P) and nitrogen (N) are essential macronutrients necessary for plant growth and development. OsPT4 is a high-affinity phosphate (Pi) transporter that has a positive impact on nutrient uptake and seed development. In this study, the expression patterns of different Pi transporter genes in germinating seeds were determined, and the relative expression of OsPT4 was induced in Pi-deficient seeds and gradually increased with the passage of germination time. The analysis of P, N, Pi, and amino acid concentrations in germinating seeds of OsPT4 mutants showed that the OsPT4 mutation caused P and N retention and a continuous reduction in multiple amino acid concentrations in germinating seeds. Transcriptome analysis and qRT-PCR results also indicated that the OsPT4 mutation inhibits the expression of genes related to P and N transportation and amino acid synthesis in germinating seeds. In addition, the paraffin section and TUNEL assay of OsPT4 mutant germinating seeds suggests that OsPT4 mutation causes programmed cell death (PCD) delayed in the aleurone layer and inhibition of leaf outgrowth. Moreover, we also found that OsPT4 was ubiquitinated by OsAIRP2, which is a C3HC4-type RING E3 Ub ligase. Our studies illustrate that OsPT4 plays a crucial role in P and N collaborative translocation and consumption in germinating seeds. It also provides a theoretical basis for the molecules and physiological mechanisms of P and N cross-talk under suppressed Pi uptake conditions.

Mutation of OsLPR3 Enhances Tolerance to Phosphate Starvation in Rice.

Low Phosphate Root (LPR) encodes a protein localized to the endoplasmic reticulum (ER) and cell wall. This gene plays a key role in responding to phosphate (Pi) deprivation, especially in remodeling the root system architecture (RSA). An identification and expression analysis of the OsLPR family in rice (Oryza sativa) has been previously reported, and OsLPR5, functioning in Pi uptake and translocation, is required for the normal growth and development of rice. However, the role of OsLPR3, one of the five members of this family in rice, in response to Pi deficiency and/or in the regulation of plant growth and development is unknown. Therefore, in this study, the roles of OsLPR3 in these processes were investigated, and some functions were found to differ between OsLPR3 and OsLPR5. OsLPR3 was found to be induced in the leaf blades, leaf sheaths, and roots under Pi deprivation. OsLPR3 overexpression strongly inhibited the growth and development of the rice but did not affect the Pi homeostasis of the plant. However, oslpr3 mutants improved RSA and Pi utilization, and they exhibited a higher tolerance to low Pi stress in rice. The agronomic traits of the oslpr3 mutants, such as 1000-grain weight and seed length, were stimulated under Pi-sufficient conditions, indicating that OsLPR3 plays roles different from those of OsLPR5 during plant growth and development, as well as in the maintenance of the Pi status of rice.

Metabolome of flue-cured tobacco is significantly affected by the presence of leaf stem.

BACKGROUND: Leaves of tobacco (Nicotiana tabacum L.) are flue-cured to use as a key industrial supply in various parts of the world. The quality of tobacco leaves is dependent on chemical components and their proportions. Generally, the stem attached to tobacco leaf is detached before curing. However, the leaf stem remains green for an extended period of time (as compared to leaf) during flue-curing. Hence, it is expected to affect the quality of tobacco's final product. RESULTS: To understand the impact of the green stem of leaf on the metabolome of flue-cured tobacco, we employed a broad targeted metabolomics approach. We selected two tobacco cultivars (Yun87 and K326) and cultivated them in five geographic locations in China. For flue-curing, leaves were harvested without a stem (L) or with an attached stem (SPL). After metabolome analysis, a total of 1027 metabolites were annotated in these samples. A variable number of metabolites were differentially accumulated between both types of leaves (depending on geographic location or cultivar) representing an influence of environment or genotype. Interestingly, only 68 metabolites were differentially accumulated between L and SPL samples irrespective of the cultivar or geographic location. These differentially accumulated metabolites belonged to major groups of primary and secondary metabolites. We have discussed the importance of identified metabolites in terms of carbon, nitrogen, and polyphenolic metabolism. CONCLUSION: The present research is the first comprehensive description of several metabolites in tobacco leaves related to the contribution of leaf stem. The current study opens novel prospects for investigating the potential of such metabolites in improving the quality of flue-cured tobacco.

Knockout of OsSWEET15 Impairs Rice Embryo Formation and Seed-Setting.

We show that the knockout of a sugar transporter gene OsSWEET15 led to a significant drop in rice fertility with around half of the knockout mutant's spikelets bearing blighted or empty grains. The rest of the spikelets bore fertile grains with a slightly reduced weight. Notably, the ovaries in the blighted grains of the ossweet15 mutants expanded after flowering but terminated their development before the endosperm cellularization stage and subsequently aborted. ß- glucuronidase (GUS) and Green Fluorescent Protein (GFP) reporter lines representing the OsSWEET15 expression showed that the gene was expressed in the endosperm tissues surrounding the embryo, which supposedly supplies nutrients to sustain embryo development. These results together with the protein's demonstrated sucrose transport capacity and plasma membrane localization suggest that OsSWEET15 plays a prominent role during the caryopsis formation stage, probably by releasing sucrose from the endosperm to support embryo development. By contrast, the empty grains were probably caused by the reduced pollen viability of the ossweet15 mutants. Investigation of ossweet11 mutant grains revealed similar phenotypes to those observed in the ossweet15 mutants. These results indicate that both OsSWEET15 and OsSWEET11 play important and similar roles in rice pollen development, caryopsis formation and seed-setting, in addition to their function in seed-filling that was demonstrated previously.

Comparative Proteomic Analysis by Isobaric Tags for the Relative and Absolute Quantification Reveals the Responses of Tobacco (Nicotiana tabacum L.) Roots to Different Soil Types.

Tobacco (Nicotiana tabacum) root affects the yield and quality of tobacco leaves. To gain insight into the responses of the tobacco root system to different soil types, we integrated morphological characteristics, the physiological index, the metabolic pathways of the root system, and the aboveground biomass of tobacco cultivated in limestone soil (LS), paddy soil (PS), and red soil (RS). Compared with plants growing in LS and PS, the chemical composition of tobacco leaves in RS tended to be coordinated. Red soil facilitated the accumulation of aboveground and belowground biomass of flue-cured tobacco and had the most significant effect on the dry matter quality of the roots. In addition, it promoted an increased root length, root surface area (RSA), root volume, and a higher number of root forks and improved root vigor and nitrate reductase (NR) activity; however, the activities of superoxide dismutase (SOD) and peroxidase (POD) were decreased. We studied differentially the abundant proteins (DAPs) of the flue-cured tobacco roots cultivated in different soil types by isobaric tags for the relative and absolute quantification (iTRAQ) of the proteomic profiles of cultivar. In total, 699, 650, and 569 differentially abundant proteins (DAPs) were identified from limestone soil (LS) vs. PS, LS vs. RS, and PS vs. RS, respectively, including 412/287, 291/359, and 323/246 up-/downregulated proteins, respectively. These DAPs were mainly involved in starch and sucrose metabolism, phenylalanine metabolism, the biosynthesis of secondary metabolites, microbial metabolism in different environments, and ribosomes. The parallel reaction monitoring (PRM) and quantitative reverse transcription PCR (qRT-PCR) analysis showed that the results of the iTRAQ proteomics were reliable. Overall, our study facilitates a new understanding of the responses of tobacco roots to different soil types at the protein level.

Differential efficacy of water lily cultivars in phytoremediation of eutrophic water contaminated with phosphorus and nitrogen.

Excessive inputs of phosphorus (P) and nitrogen (N) trigger eutrophication of the water bodies, which promotes the undesirable growth of algal bloom and deterioration of the water quality, and aquatic biodiversity. Macrophytes provide an environmentally benign and economically viable paradigm for the ecological restoration of eutrophic aquatic ecosystems. Water lily (Nymphaea) is largely used as ornamental plant for landscaping, and it has been documented that water lily possesses the potentiality in mitigating polluted aquatic environments. In the present study, water lily cultivars Nymphaea Texas Dawn (NTD), Nymphaea Colorado (NC), Nymphaea Madame Wilfron Gonnère (NMWG), and Nymphaea Sunshine Princess (NSP) were investigated for their potency in alleviating the eutrophication. The concentrations of total P and total N were significantly higher in the leaves of NC and NSP compared with NTD and NMWG. Therefore, NC and NSP were selected for subsequent studies to decipher their recuperation efficacy on eutrophic waters at different growth stages. NC and NSP significantly reduced the concentrations of eutrophication indicators i.e., total P, NH4+-N, and chemical oxygen demand in different gradients of the simulated eutrophic water in a growth-dependent manner. On the contrary, NC and NSP triggered a significant increase in the concentration of dissolved oxygen particularly at the seedling stage. Notably, the concentrations of total P (shoot and root) and total N (root) were relatively higher in NSP than NC. The study thus revealed a growth-dependent differential efficacy of NSP and NC in mitigating the different eutrophic waters.

Does Sulfoquinovosyl Diacylglycerol Synthase OsSQD1 Affect the Composition of Lipids in Rice Phosphate-Deprived Root?

Lipids are the essential components of the cell intracellular and plasma membranes. Sulfoquinovosyldiacylglycerol (SQDG) is a glycolipid; glycolipids can replace phospholipids in maintaining phosphate (Pi) homeostasis in plants which are undergoing Pi starvation. Sulfoquinovosyl diacylglycerol synthase 1 (OsSQD1) is a critical enzyme in the first step of catalyzation in the formation of SQDG in rice. In this study, the expression pattern of different zones in roots of OsSQD1 in response to different Pi conditions is examined, and it is found that OsSQD1 is highly expressed in lateral roots under Pi-sufficient and -deficient conditions. The root phenotype observation of different OsSQD1 transgenic lines suggests that the knockout/down of OsSQD1 inhibits the formation and growth of lateral roots under different Pi conditions. Additionally, the lipid concentrations in OsSQD1 transgenic line roots indicate that OsSQD1 knockout/down decreases the concentration of phospholipids and glycolipids in Pi-starved roots. The OsSQD1 mutation also changes the composition of different lipid species with different acyl chain lengths, mainly under Pi-deprived conditions. The relative transcript expression of genes relating to glycolipid synthesis and phospholipid degradation is estimated to help study the mechanism by which OsSQD1 exerts an influence on the alteration of lipid composition and concentration in Pi-starved roots. Moreover, in Pi-starved roots, the knockout of OsSQD1 decreases the unsaturated fatty acid content of phospholipids and glycolipids. To summarize, the present study demonstrates that OsSQD1 plays a key role in the maintenance of phospholipid and glycolipid composition in Pi-deprived rice roots, which may influence root growth and development under Pi-deprived conditions.

Overexpression of OsPHR3 improves growth traits and facilitates nitrogen use efficiency under low phosphate condition.

Phosphorus (P) and nitrogen (N) are both essential macronutrients for maintaining plant growth and development. In rice (Oryza sativa L.), OsPHR3 is one of the four paralogs of PHR1, which acts as a central regulator of phosphate (Pi) homeostasis, as well being involved in N homeostasis. However, the functions of OsPHR3 in N utilization under different Pi conditions have yet to be fully studied. In this study, we aimed to dissect the effect of OsPHR3-overexpression on N utilization under Pi deficient regimes. Biochemical, molecular and physiological assays were performed to determine the N-influx, translocation, and accumulation in OsPHR3-overexpressing rice lines, grown under Pi-sufficient and -deficient conditions, in both hydroponic and soil systems. Furthermore, important agronomic traits of these plants were also evaluated. The overexpression of OsPHR3 increased N uptake under Pi stress regimes. Increased N uptake also elevated total N concentrations in these plants by inducing N transporter genes expression. Furthermore, overexpression of OsPHR3 increased N use efficiency, 1000-grain weight and grain yield under different Pi conditions. We established new findings that OsPHR3-overexpression facilitates N utilization under Pi deficient conditions. This will help achieving higher yields by coordinating the utilization of N and P.

Sulfoquinovosyl diacylglycerol synthase 1 impairs glycolipid accumulation and photosynthesis in phosphate-deprived rice.

Phosphate (Pi)-starved crops utilize phospholipids as a source for internal Pi supply by replacing non-phosphorus glycolipids. In rice, sulfoquinovosyl diacylglycerol synthase 1 (OsSQD1) functions as a key enzyme in the first step to catalyze sulfoquinovosyldiacylglycerol (SQDG) formation. Here we study differential expression of OsSQD1 in response to Pi, nitrogen, potassium, and iron-deficiencies in rice. Electrophoretic mobility shift assay suggested that OsSQD1 is regulated by OsPHR2 (Phosphate Starvation Response2), a MYB (v-myb avian myeloblastosis viral oncogene homolog) domain-containing transcription factor. The concentrations of different lipid species in ossqd1 knockout mutant demonstrated that OsSQD1 silencing increased the phospholipid content and altered fatty acid composition under Pi-deficiency. Moreover, OsSQD1 silencing reduces glycolipid accumulation under Pi-deficiency, and triggered the saturation of fatty acids in phospholipids and glycolipids treated with different Pi regimes. Relative amounts of transcripts related to phospholipid degradation and glycolipid synthesis were assessed to explore the mechanism by which OsSQD1 exerts an effect on lipid homeostasis under P-deficiency. Furthermore, OsSQD1 silencing inhibited photosynthesis, especially under Pi-deficient conditions, by down-regulating glycolipids in rice shoots. Taken together, our study reveals that OsSQD1 plays a key role in lipid homeostasis, especially glycolipid accumulation under Pi-deficiency, which results in the inhibition of photosynthesis.

The ferroxidase LPR5 functions in the maintenance of phosphate homeostasis and is required for normal growth and development of rice.

Members of the Low Phosphate Root (LPR) family have been identified in rice (Oryza sativa) and expression analyses have been conducted. Here, we investigated the functions of one of the five members in rice, LPR5. qRT-PCR and promoter-GUS reporter analyses indicated that under Pi-sufficient conditions OsLPR5 was highly expressed in the roots, and specific expression occurred in the leaf collars and nodes, and its expression was increased under Pi-deficient conditions. In vitro analysis of the purified OsLPR5 protein showed that it exhibited ferroxidase activity. Overexpression of OsLPR5 triggered higher ferroxidase activity, and elevated concentrations of Fe(III) in the xylem sap and of total Fe in the roots and shoots. Transient expression of OsLPR5 in Nicotiana benthamiana provided evidence of its subcellular localization to the cell wall and endoplasmic reticulum. Knockout mutation in OsLPR5 by means of CRISPR-Cas9 resulted in adverse effects on Pi translocation, on the relative expression of Cis-NATOsPHO1;2, and on several morphological traits, including root development and yield potential. Our results indicate that ferroxidase-dependent OsLPR5 has both a broad-spectrum influence on growth and development in rice as well as affecting a subset of physiological and molecular traits that govern Pi homeostasis.

OsSQD1 at the crossroads of phosphate and sulfur metabolism affects plant morphology and lipid composition in response to phosphate deprivation.

In phosphate (Pi)-deprived Arabidopsis (Arabidopsis thaliana), phosphatidylglycerol (PG) is substituted by sulfolipid for maintaining Pi homeostasis. Sulfoquinovosyl diacylglycerol1 (AtSQD1) encodes a protein, which catalyzes uridine diphosphate glucose (UDPG) and sulfite (SO32- ) to UDP-sulfoquinovose, which is a key component in the sulfolipid biosynthetic pathway. In this study, a reverse genetics approach was employed to decipher the function of the AtSQD1 homolog OsSQD1 in rice. Differential expressions of OsSQD1 in different tissue and response to -P and -S also detected, respectively. The in vitro protein assay and analysis suggests that OsSQD1 is a UDP-sulfoquinovose synthase. Transient expression analysis showed that OsSQD1 is located in the chloroplast. The analyses of the knockout (ossqd1) and knockdown (Ri1 and Ri2) mutants demonstrated reductions in Pi and total P concentrations, 32 Pi uptake rate, expression levels of Pi transporters and altered developmental responses of root traits, which were accentuated during Pi deficiency. The inhibitory effects of the OsSQD1 mutation were also evident in the development of reproductive tissue. Furthermore, OsSQD1 differently affects lipid composition under different Pi regime affects sulfur (S) homeostasis. Together, the study revealed that OsSQD1 affects Pi and S homeostasis, and lipid composition in response to Pi deprivation.

OsPDR2 mediates the regulation on the development response and maintenance of Pi homeostasis in rice.

Inorganic orthophosphate (Pi), a major form of essential macronutrient phosphorus (P), is available in rhizosphere for acquisition and assimilation by plants. However, the limited availability of Pi in soils affects the growth and development of plants. In Arabidopsis thaliana (Arabidopsis), Phosphate Deficiency Response2 (AtPDR2), interacts genetically with Low Phosphate Root1 (AtLPR1) in the endoplasmic reticulum (ER) and plays a key role in the inhibition of primary root growth (PRG) during Pi deficiency. However, the role of OsPDR2, the homolog of AtPDR2, either in roots response to Pi deficiency and/or in growth and development has not been elucidated as yet. Therefore, qRT-PCR was employed to determine the spatiotemporal effects and the availability of Pi on the expression of OsPDR2. OsPDR2 showed variable levels of relative expression pattern in vegetative and/or reproductive tissues analyzed at different stages of growth and development (5-17 weeks). Transient expression analysis revealed its subcellular localization to the ER. Further, the reverse genetics approach was employed for determining the function of OsPDR2 by generating RNAi lines (Ri2, Ri9, and Ri18). The study revealed significant inhibitory effects of RNAi-mediated suppression of OsPDR2 on the development of root, male reproductive traits, and yield. Moreover, 32P isotope labeling and split-root experiments under different Pi regime with RNAi lines revealed the function of OsPDR2 in regulating homeostasis of Pi.

Expression of New Pteris vittata Phosphate Transporter PvPht1;4 Reduces Arsenic Translocation from the Roots to Shoots in Tobacco Plants.

Arsenic-hyperaccumulator Pteris vittata is efficient in As uptake, probably through phosphate transporters (Pht). Here, for the first time, we cloned a new PvPht1;4 gene from P. vittata and investigated its role in arsenate (AsV) uptake and transport in yeast and transgenic tobacco plants. On the basis of quantitative real-time polymerase chain reaction (qRT-PCR), PvPht1;4 was abundantly expressed in P. vittata fronds and roots, with its transcripts in the roots being induced by both P deficiency and As exposure. PvPht1;4 was localized to the plasma membrane, which complemented a yeast-mutant defective in P uptake and showed higher P transport affinity than PvPht1;3. Under AsV exposure, PvPht1;4 yeast transformants showed comparable tolerance as PvPht1;3, but higher As accumulation than PvPht1;2 transformants, indicating that PvPht1;4 had considerable AsV and P transport activity. However, in soil and hydroponic experiments, PvPht1;4 expressing tobacco lines accumulated 26-44 and 37-55% lower As in the shoots than wild type plants, with lower root-to-shoot As translocation. In the roots of PvPht1;4 lines, higher glutathione (GSH) contents and expression levels of GSH synthetase gene NtGSH2 were observed. In addition, the transcripts of AsIII-GSH transporter NtABCC1 in PvPht1;4 lines were upregulated. The data suggested that PvPht1;4 lines probably detoxified As by reducing AsV to AsIII, which was then complexed with GSH and stored in the root vacuoles, thereby reducing As translocation in transgenic tobacco. Given its strong AsV transport capacity, expression of PvPht1;4 provides a new molecular approach to reduce As accumulation in plant shoots.

Mutation of the chloroplast-localized phosphate transporter OsPHT2;1 reduces flavonoid accumulation and UV tolerance in rice.

Phosphorus (P) is an essential macronutrient required for plant development and production. The mechanisms regulating phosphate (Pi) uptake are well established, but the function of chloroplast Pi homeostasis is poorly understood in Oryza sativa (rice). PHT2;1 is one of the transporters/translocators mediating Pi import into chloroplasts. In this study, to gain insight into the role of OsPHT2;1-mediated stroma Pi, we analyzed OsPHT2;1 function in Pi utilization and photoprotection. Our results showed that OsPHT2;1 was induced by Pi starvation and light exposure. Cell-based assays showed that OsPHT2;1 localized to the chloroplast envelope and functioned as a low-affinity Pi transporter. The ospht2;1 had reduced Pi accumulation, plant growth and photosynthetic rates. Metabolite profiling revealed that 52.6% of the decreased metabolites in ospht2;1 plants were flavonoids, which was further confirmed by 40% lower content of total flavonoids compared with the wild type. As a consequence, ospht2;1 plants were more sensitive to UV-B irradiation. Moreover, the content of phenylalanine, the precursor of flavonoids, was also reduced, and was largely associated with the repressed expression of ADT1/MTR1. Furthermore, the ospht2;1 plants showed decreased grain yields at relatively high levels of UV-B irradiance. In summary, OsPHT2;1 functions as a chloroplast-localized low-affinity Pi transporter that mediates UV tolerance and rice yields at different latitudes.

OsSIZ2 regulates nitrogen homeostasis and some of the reproductive traits in rice.

Small ubiquitin-related modifier (SUMO) is a post-translational modification of proteins that has important roles in plant growth and development as well as nutrition study. OsSIZ1, a SUMO E3 ligase in rice (Oryza sativa), exerts regulatory influence on nitrogen (N) homeostasis. Here, we investigated the biological function of OsSIZ2, a paralog of OsSIZ1, in the responses to nitrogen, anther dehiscence, and seed length using a reverse genetics approach. The expression of OsSIZ2 was increased during N deficiency. Under -N condition, total N concentration in the root of OsSIZ2-Ri plants and ossiz2 was significantly increased compared with wild type. Further, 15N-labelled uptake assay revealed the role of OsSIZ2 in acquisition and mobilization of N. Moreover, qRT-PCR analyses revealed that several genes involved in the maintenance of N homeostasis were altered in OsSIZ2 mutants. In addition, ossiz2 indicated obvious defects in anther dehiscence, pollen fertility, and seed set percentage. Interestingly, however, the seed length was longer in the mutant compared with wild type. Overall, these results suggest pivotal roles of OsSIZ2 in regulating homeostasis of N and different agronomic traits including anther and seed development.

OsPHR3 affects the traits governing nitrogen homeostasis in rice.

BACKGROUND: Phosphate (Pi) and Nitrogen (N) are essential macronutrients required for plant growth and development. In Arabidopsis thaliana (Arabidopsis), the transcription factor PHR1 acts as a Pi central regulator. PHL1 is a homolog of PHR1 and also plays a role in maintaining Pi homeostasis. In rice (Oryza sativa), OsPHR1-4 are the orthologs of PHR1 and have been implicated in regulating sensing and signaling cascades governing Pi homeostasis. RESULTS: Here the role of OsPHR3 was examined in regulating the homeostasis of N under different Pi regimes. Deficiencies of different variants of N exerted attenuating effects on the relative expression levels of OsPHR3 in a tissue-specific manner. For the functional characterization of OsPHR3, its Tos17 insertion homozygous mutants i.e., osphr3-1, osphr3-2, and osphr3-3 were compared with the wild-type for various morphophysiological and molecular traits during vegetative (hydroponics with different regimes of N variants) and reproductive (pot soil) growth phases. During vegetative growth phase, compared with the wild-type, OsPHR3 mutants showed significant variations in the adventitious root development, influx rates of 15N-NO3- and 15N-NH4+, concentrations of total N, NO3- and NH4+ in different tissues, and the relative expression levels of OsNRT1.1a, OsNRT2.4, OsAMT1;1, OsNia1 and OsNia2. The effects of the mutation in OsPHR3 was also explicit on the seed-set and grain yield during growth in a pot soil. Although Pi deficiency affected total N and NO3- concentration, the lateral root development and the relative expression levels of some of the NO3- and NH4+ transporter genes, its availability did not exert any notable regulatory influences on the traits governing N homeostasis. CONCLUSIONS: OsPHR3 plays a pivotal role in regulating the homeostasis of N independent of Pi availability.

Characterization of the loss-of-function mutant NH101 for yield under phosphate deficiency from EMS-induced mutants of rice variety Nagina22.

In earlier studies at IIRR, Hyderabad, screening of ∼2000 EMS mutants of the rice variety Nagina22 (N22) resulted in the identification of 11 loss-of-function mutants with zero grain yield in Pi-deprived soil under field condition. Among these mutants, NH101 was selected for comparative analyses with N22 for various morphophysiological and/or molecular traits during growth in a hydroponic system (7 d) and in a pot soil (50% flowering) under different Pi regime. The total length of the seminal and adventitious roots, agronomic traits (panicle length and unfilled spikelet/panicle), activities of the antioxidant enzymes (SOD, POD, and APX), and the relative expression levels of the genes involved in the maintenance of Pi homeostasis (MPH) i.e., OsPHR2, SPX1/2 OsPT4, 6, and 8 showed significant increase in the Pi-deprived mutant compared with N22. Whereas, some of the traits showed significant reduction in NH101 than N22 such as number of tillers and filled spikelets/panicle, yield, contents of Pi and externally secreted APase, activity of CAT, and the relative expression levels of MPH genes i.e., OsmiR399a, OsPHO1;2, OsIPS1, OsPAP10a, OsPT2, 9, and 10. The study highlighted wide spectrum differential effects of the mutation in NH101 on various traits that play important roles governing the maintenance of Pi homeostasis. This mutant thus provides a rich repository of genetic material amenable for the identification of the genes that are pivotal for Pi use efficiency.