Phosphorus Use Efficiency Research Articles

Roles, Regulation, and Agricultural Application of Plant Phosphate Transporters.

Phosphorus (P) is an essential mineral nutrient for plant growth and development. Low availability of inorganic phosphate (orthophosphate; Pi) in soil seriously restricts the crop production, while excessive fertilization has caused environmental pollution. Pi acquisition and homeostasis depend on transport processes controlled Pi transporters, which are grouped into five families so far: PHT1, PHT2, PHT3, PHT4, and PHT5. This review summarizes the current understanding on plant PHT families, including phylogenetic analysis, function, and regulation. The potential application of Pi transporters and the related regulatory factors for developing genetically modified crops with high phosphorus use efficiency (PUE) are also discussed in this review. At last, we provide some potential strategies for developing high PUE crops under salt or drought stress conditions, which can be valuable for improving crop yields challenged by global scarcity of water resources and increasing soil salinization.

Significance of the localization of phosphorus among tissues on a cross-section of leaf lamina of Bornean tree species for phosphorus-use efficiency

Abstract:A greater relative allocation of phosphorus (P) to photosynthetically active cells functions to maintain a rapid photosynthesis under P limitation, and may be a key mechanism of plants to use P efficiently. This mechanism has not been studied in tropical trees despite the productivity of tropical forests often being limited by P. In this study, the spatial distribution of P among tissues on a cross-section of leaf lamina was analysed for 13 tree species from P-limited sites on Mount Kinabalu, Borneo. Most species showed greater P concentration in palisade mesophyll than in spongy mesophyll and epidermal tissues, suggesting that tropical trees under P limitation localize foliar P in photosynthetic palisade mesophyll.

Effects of nitrogen and phosphorus addition on leaf thermal tolerance in different provenances of Quercus variabilis

To explore potential effects of soil nutrient on leaf thermal tolerance across geographical origins, five provenance, i.e., Chengbu of Hunan (CB), Zigui of Hubei (ZG), Neixiang of Henan (NX), Lincheng of Heibei (LC) and Pinggu of Beijing (PG), seedlings of Quercus variabilis were cultivated under nitrogen and phosphorus addition. Leaf thermal tolerance parameters (cold, heat and span), nutrient concentrations (nitrogen and phosphorus), nitrogen use efficiency (NUE) and phosphorus use efficiency (PUE), as well as non-structural carbohydrate (soluble sugar and starch) concentrations were analyzed. The results were shown as follows: Nutrient absorption and utilization efficiency varied between oak origins with no obvious geographical trends. PG had higher nutrient use efficiency (NUE and PUE), whereas NX had lower PUE under all treatments. CB had the highest PUE under phosphorus addition. Compared with the control, nutrient addition increased the cold tolerance of PG and LC, and to some extent, increased the heat tolerance of the three middle provenances (ZG, NX, LC). However, the thermal span was opposite to the cold tolerance, as nutrient addition decreased the thermal span of PG and LC but increased that of NX. The leaf cold tolerance had significantly positive correlation with soluble sugar concentration, while the heat tolerance negatively and positively correlated with leaf phosphorus and ratio of nitrogen to phosphorus, respectively. No significant correlation was found between leaf thermal span and leaf chemical substances. To sum up, nutrient use efficiency varying in provenances might be contributed by the original habitats and consequently presented with some local adaptation characteristics, which complicated the response of thermal tolerance to nutrient addition.

Promoting Growth, Yield, and Phosphorus-Use Efficiency of Crops in Maize–Wheat Cropping System by Using Polymer-Coated Diammonium Phosphate

ABSTRACTField experiments were conducted at Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan, to check the effect of polymer-coated diammonium phosphate (DAP) on maize–wheat cropping system. Different rates of polymer-coated and uncoated phosphorus (P) were applied first to maize then followed by wheat after harvesting of maize on same field. Results showed that application of 100% of recommended P from polymer-coated DAP increased plant height (10%), chlorophyll content (4%), biological yield (17%), grain yield (36%), agronomic efficiency (43%), and nitrogen, phosphorus, and potassium contents of maize produces, while in case of wheat 75% recommended P from polymer-coated DAP increased plant height (6%), chlorophyll content (18%), biological yield (20%), grain yield (14%), agronomic efficiency (72%), and nitrogen, phosphorus, and potassium contents of grains and straw as compared with uncoated DAP. So, it can be summarized that polymer-coated DAP can effectively improve growth, yield, and phosphorus-use efficiency of maize and wheat crop.

Effect of phosphorus on arsenic uptake and metabolism in rice cultivars differing in phosphorus use efficiency and response.

A hydroponic experiment was carried out to investigate the effect of phosphorus (P) nutrition on arsenic (As) uptake and translocation within the seedlings of rice cultivars. The experiment occurred in three stages: I 5 days of acclimatization (nutritive solution); II 10 days under P (0.0 and 0.09 mM) and As (0.0 and 100 mM) treatments; III 5 days under recovery. The As exposure had significant effect reducing dry weights of shoots or roots, resulted in elevated concentrations of As in shoot tissues. BR-IRGA 409 showed the highest susceptibility to As in biomass production and root system parameters regardless the P level. This cultivar showed contrasting responses of As translocation to shoot tissue dependent on P levels, with the highest As concentration under low P and lowest under normal P levels. P nutrition was most striking on plants recovery for all cultivars under As exposure. Clearer separation of cultivars for phosphorus use efficiency (PUE) occurred at lower shoot P contents, that was, at higher levels of P deficiency stress. IRGA 424 showed higher PUE as compared to the others cultivars. Our results go some way to understanding the role of P nutrition in controlling the effects of As in rice shoots.

Characterization of genotypic variability associated to the phosphorus bioavailability in peanut (Arachis hypogaea L.)

In order to assess genotypic variability in some peanut genotypes depending on phosphorus availability, both effects of tri-calcium phosphate (TCP) and inoculation by Bradyrhizobium strain (BR) on morphological and physiological parameters were studied in five peanut genotypes (Arachis hypogaea L.), originated from two Algerian areas (Northern and Southern). The results obtained during the flowering stage of crop development, confirmed the positive effect of the contribution of tri-calcium phosphate (TCP) with Bradyrhizobium strains on the morphological characters (shoot biomass, root biomass, nodular biomass and leaf) and the physiological (nitrogenase activity, phosphorus absorption efficiency by roots (RPAE) and phosphorus use efficiency (PUE)) for the peanut genotypes cultivated in this experiment. Among five genotypes tested, it was noted that the Southern genotypes were more efficient to use TCP in the presence of Bradyrhizobium strain after a screening of these local genotypes, in particular, with phosphorus use efficiency (PUE) and shoot biomass production.

Bacterial impregnation of mineral fertilizers improves yield and nutrient use efficiency of wheat.

The fertilizer use efficiency (FUE) of agricultural crops is generally low, which results in poor crop yields and low economic benefits to farmers. Among the various approaches used to enhance FUE, impregnation of mineral fertilizers with plant growth-promoting bacteria (PGPB) is attracting worldwide attention. The present study was aimed to improve growth, yield and nutrient use efficiency of wheat by bacterially impregnated mineral fertilizers. Results of the pot study revealed that impregnation of diammonium phosphate (DAP) and urea with PGPB was helpful in enhancing the growth, yield, photosynthetic rate, nitrogen use efficiency (NUE) and phosphorus use efficiency (PUE) of wheat. However, the plants treated with F8 type DAP and urea, prepared by coating a slurry of PGPB (Bacillus sp. strain KAP6) and compost on DAP and urea granules at the rate of 2.0 g 100 g-1 fertilizer, produced better results than other fertilizer treatments. In this treatment, growth parameters including plant height, root length, straw yield and root biomass significantly (P ≤ 0.05) increased from 58.8 to 70.0 cm, 41.2 to 50.0 cm, 19.6 to 24.2 g per pot and 1.8 to 2.2 g per pot, respectively. The same treatment improved grain yield of wheat by 20% compared to unimpregnated DAP and urea (F0). Likewise, the maximum increase in photosynthetic rate, grain NP content, grain NP uptake, NUE and PUE of wheat were also recorded with F8 treatment. The results suggest that the application of bacterially impregnated DAP and urea is highly effective for improving growth, yield and FUE of wheat. © 2017 Society of Chemical Industry.

Generation mean analysis of phosphorus-use efficiency in freely nodulating soybean crosses grown in low-phosphorus soil

Freely nodulating soybean genotypes vary in their phosphorus (P) uptake and P-use efficiency (PUE) in low-P soils. Understanding the genetic basis of these genotypes’ performance is essential for effective breeding. To study the inheritance of PUE, we conducted crosses using two high-PUE genotypes, two moderate-PUE genotypes and two inefficient-PUE genotypes, and obtained F1, F2, BC1 and BC2 populations. The inheritance of PUE was evaluated using a randomized complete block design. A generation mean analysis of phenotypic data showed that PUE was heritable, with complex inheritance patterns and the presence of additive, dominance and epistatic gene effects. Seed P, shoot P, root P, P-incorporation efficiency and PUE were largely quantitatively inherited traits. There were dominance, additive × additive and dominance × dominance gene effects on PUE, grain yield, shoot dry weight, 100-seed weight, root dry weight and shoot dry matter per unit P for populations grown under low-P conditions. Dominance effects were generally greater than additive effects on PUE-related indices. These PUE indices can be used to select P-efficient soybean genotypes from segregating populations.

Efficiency of Phosphorus Use for Dinitrogen Fixation Varies between Common Bean Genotypes under Phosphorus Limitation

Core Ideas Phosphorus use efficiency may be classified as trait for P‐deficiency tolerance. Low soil P availability is a limiting factor of the rhizobial symbiosis. The increase of P content may be involved in the regulation of nodulation. Low P availability in the soil is a major constraint to legume production, and efforts are being made to identify legume genotypes with tolerance to low P and greater phosphorus use efficiency (PUE) for N2 fixation. Common bean (Phaseolus vulgaris L.) genotypes vary in their adaptation to low‐P soils. To investigate to what extent this variation may be related to PUE for N2 fixation, six recombinant inbred lines (RILs) of common bean contrasting in PUE for symbiotic N2 fixation, namely RILs 147, 115, 104, 83, 34, and 29 were studied in the field conditions during four growing seasons from 2011 to 2015. We collected biomass (aboveground and belowground) at flowering stage, and both samples were analyzed P content. Results indicate that low‐P availability in the soil significantly limited plant growth, nodulation, and N2 fixation for all common bean RILs though with highest extent for common bean RILs 147, 83, and 29, whereas in this soil, common bean RILs 34 and 104 showed highest PUE for their N2 fixation. The genotypes with high PUE for N2 fixation showed greater mycorrhizal‐plant symbiosis activity rate than the genotypes with low PUE for N2 fixation. We also found a significant correlation between nodule biomass and nodule P content for all common bean RILs. We conclude that quantifying PUE for N2 fixation may contribute to characterize the level of adaptation of N2–fixing legumes to low‐P soils.

Phosphorus efficient potato cultivars for Nilgiris

Field experiments were conducted at Central Potato Research Station, Muthorai, the Nilgiris, Tamil Nadu forthree years with seven potato cultivars under four levels of phosphorus application to evaluate their phosphorususe efficiency. Cultivars Kufri Neelima and Kufri Swarna were found more P efficient because of their higherrelative biomass production, tuber yield efficiency index, harvest index, agronomic use efficiency (AUE) and Puptake efficiency. These two cultivars produced higher tuber yields under no P and at Pmax of standard variety. The cultivars Kufri Girdhari, Kufri Jyoti and Kufri Himalini proved P responsive as they responded well to itsapplication and produced very low yields under no P application. Higher root biomass in these two efficientcultivars could be the reason behind their higher P use efficiency in comparison to other cultivars. The two Pefficient potato cultivars also happened to be resistant to potato cyst nematode, which are very common andserious problem in Nilgiris. The mechanism to have resistance against PCN, whose cysts emerge only in thepresence of root exudates of susceptible potato cultivars, could also have benefitted those cultivars to showmore efficiency in native P utilization. Further investigations are required to find out the exact mechanism of Pefficiency in these two PCN resistant cultivars.

Age-related morphological and physiological responses of irrigated rice to declined soil phosphorus and potassium availability

Inorganic fertilisers need to be applied only when the inherent soil fertility alone cannot supply the plant nutrient demand for rice. When managing such systems, identification of the most sensitive morphological and/or physiological characteristics of a rice plant and the growth stage at which those responses appear when soil phosphorus (P) and potassium (K) availabilities have declined are important. Such a practice will increase fertiliser-use efficiency and enhance environmental sustenance. Experiment was conducted in a field differing in initial soil P and K availabilities due to the application of four fertiliser treatments for three consecutive seasons. Observations in this experiment were made in the fourth season. Four fertiliser treatments were the application of (i) both P and K (P1K1), (ii) only P (P1K0), (iii) only K (P0K1), and (iv) no P and K (P0K0). Rice variety Bg300 was grown. Shoot samples were obtained at two-week intervals, while root and soil samples were collected using a soil core up to 80 cm depth at physiological maturity. At physiological maturity, root length, diameter, and root length density were not responsive to the declined soil P and K availability, whereas the total above-ground dry weight (DW) reduced in P- and K-deficient plots. Shoot physiological responses [i.e. reduced green leaf P and K concentrations, and increased phosphorus-use efficiency (PUE) and potassium-use efficiency (KUE)] were more prominent than shoot morphological responses (i.e. plant height, number of tillers, and total above-ground DW), throughout the growth cycle. The intensity (i.e. statistical significance) and duration of the appearance of K deficiency symptoms were lower than those of P. The most sensitive growth stage of rice to slight deficiencies of P and K was the tillering stage. This knowledge on the morphological and physiological shoot and root responses that can be observed during the lifecycle of a rice plant, and the growth stage(s) at which those responses are prominent in response to declining soil P and K availability can be used when identifying the development of soil P and K limitations hindering the optimal growth of rice plant, and sustaining rice cropping systems.

Strand-specific RNA-Seq transcriptome analysis of genotypes with and without low-phosphorus tolerance provides novel insights into phosphorus-use efficiency in maize.

BackgroundPhosphorus (P) stress is a global problem in maize production. Although macro/microarray technologies have greatly increased our general knowledge of maize responses to P stress, a greater understanding of the diversity of responses in maize genotypes is still needed.ResultsIn this study, we first evaluated the tolerance to low P of 560 accessions under field conditions, and selected the low P-tolerant line CCM454 and the low P-sensitive line 31778 for further research. We then generated 24 strand-specific RNA libraries from shoots and roots of CCM454 and 31778 that had been subjected to P stress for 2 and 8 days. The P deficiency-responsive genes common to CCM454 and 31778 were involved in various metabolic processes, including acid phosphatase (APase) activity. Determination of root-secretory APase activities showed that the induction of APase by P stress occurred much earlier in CCM454 than that in 31778. Gene Ontology analysis of differentially expressed genes (DEGs) and CAT/POD activities between CCM454 and 31778 under P-sufficient and -deficient conditions demonstrated that CCM454 has a greater ability to eliminate reactive oxygen species (ROS) than 31778. In addition, 16 miRNAs in roots and 12 miRNAs in shoots, including miRNA399s, were identified as DEGs between CCM454 and 31778.ConclusionsThe results indicate that the tolerance to low P of CCM454 is mainly due to the rapid responsiveness to P stress and efficient elimination of ROS. Our findings increase the understanding of the molecular events involved in the diversity of responses to P stress among maize accessions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0903-4) contains supplementary material, which is available to authorized users.

Regulation of phosphorus uptake and utilization: transitioning from current knowledge to practical strategies.

Phosphorus is a poorly bioavailable macronutrient that is essential for crop growth and yield. Overuse of phosphorus fertilizers results in low phosphorus use efficiency (PUE), has serious environmental consequences and accelerates the depletion of phosphorus mineral reserves. It has become extremely challenging to improve PUE while preserving global food supplies and maintaining environmental sustainability. Molecular and genetic analyses have revealed the primary mechanisms of phosphorus uptake and utilization and their relationships to phosphorus transporters, regulators, root architecture, metabolic adaptations, quantitative trait loci, hormonal signaling and microRNA. The ability to improve PUE requires a transition from this knowledge of molecular mechanisms and plant architecture to practical strategies. These could include: i) the use of arbuscular mycorrhizal fungal symbioses for efficient phosphorus mining and uptake; ii) intercropping with suitable crop species to achieve phosphorus activation and mobilization in the soil; and iii) tissue-specific overexpression of homologous genes with advantageous agronomic properties for higher PUE along with breeding for phosphorus-efficient varieties and introgression of key quantitative trait loci. More effort is required to further dissect the mechanisms controlling phosphorus uptake and utilization within plants and provide new insight into the means to efficiently improve PUE.

Seedling growth responses to phosphorus reflect adult distribution patterns of tropical trees.

Soils influence tropical forest composition at regional scales. In Panama, data on tree communities and underlying soils indicate that species frequently show distributional associations to soil phosphorus. To understand how these associations arise, we combined a pot experiment to measure seedling responses of 15 pioneer species to phosphorus addition with an analysis of the phylogenetic structure of phosphorus associations of the entire tree community. Growth responses of pioneers to phosphorus addition revealed a clear tradeoff: species from high-phosphorus sites grew fastest in the phosphorus-addition treatment, while species from low-phosphorus sites grew fastest in the low-phosphorus treatment. Traits associated with growth performance remain unclear: biomass allocation, phosphatase activity and phosphorus-use efficiency did not correlate with phosphorus associations; however, phosphatase activity was most strongly down-regulated in response to phosphorus addition in species from high-phosphorus sites. Phylogenetic analysis indicated that pioneers occur more frequently in clades where phosphorus associations are overdispersed as compared with the overall tree community, suggesting that selection on phosphorus acquisition and use may be strongest for pioneer species with high phosphorus demand. Our results show that phosphorus-dependent growth rates provide an additional explanation for the regional distribution of tree species in Panama, and possibly elsewhere.

Water, nitrogen and phosphorus use efficiencies of four tree species in response to variable water and nutrient supply

Background and Aims The commonly observed trade-off between plant water use efficiency (WUE) and nitrogen use efficiency (NUE) has been attributed to physiological constraints in the leaf. We examined if a similar trade-off can occur between WUE and phosphorus use efficiency (PUE) and if changes in NUE and PUE in response to water and nutrient supply can be related to microbial N and P immobilisation.

Genetic variations and correlation analysis of N and P traits in Pinus massoniana under combined conditions of N deposition and P deficiency

Significant genetic variations in N and P nutritional traits exist under combined conditions of soil P deficiency and N deposition and interactively contribute to growth benefits. Forest ecosystems encounter combined conditions of soil phosphorus (P) deficiency and atmospheric nitrogen (N) deposition. As such, determining genetic variations and interactions of N and P nutritional traits is important for silviculture. Low N (LN) and high N (HN) were combined with three P treatments in a pot experiment with five full-sib families of Masson pine (Pinus massoniana). The three P treatments are: low P in soil profile (low-P condition, LP), enriched P in topsoil and poor P in subsoil (medium–low-P condition, MLP), and high P in soil profile (high-P condition, HP). P acquisition was more significant for growth benefits than P utilization under LP. Growth response to N was higher under MLP and HP than that under LP because of more balanced plant N:P ratios in the two former conditions. Under HN, there were significant correlation between nitrogen acquisition efficiency (NAE) and phosphorus use efficiency (PUE) and they interactively contributed to growth promotion under N deposition. Significant genetic variations, as well as large heritability of growth and N and P nutritional traits, were detected under all N–P conditions. This finding indicated the feasibility of breeding families with improved nutrient efficiency under N–P conditions.

Scaling-up of toria (Brassica campestris) productivity using diverse agro-techniques in eastern Himalayan region

Field experimentation on toria (Brassica campestris L.) was carried out with the major objective of utilizing the fallow land after rainy season by following suitable management practices in the region. Results revealed that under conventional tillage, roots were 39.1% longer and 36.8% heavier biomass, contrarily no tillage had 6% more soil organic carbon. The seed yield improved by 44.8% with minimum tillage over no tillage. Crop sown on 15 October obtained 16.9-47.6% additional seed yield over before and after sown crops, but line sowing evidenced 22.1% higher seed yield than the broadcasting. Planting geometry with 30x15 cm noticed 3.1-32.9% more seed yield. Nitrogen application at 75 kg/ha had 5.3-47% improvement of seed yield, whereas nitrogen use efficiency was highest with 50 kg/ha. Phosphorus application at 50 kg/ha added 61.5% more yield, whereas phosphorus-use efficiency was highest at 25 kg/ha. Twice irrigation at 30 and 60 days after sowing (DAS) noticed 40.5% extra seed yield, contrary water-use efficiency was highest with single irrigation at 30 DAS over no irrigation. Hand weeding twice at 25 and 50 DAS supplemented the seed yield by 52.6% with 55.7% weed control efficiency over no weeding. Adoption of better package of practices in newer area under existing cropping system will play a key role in future yield improvement. Therefore, as per the resource availability feasible technologies may harness higher seed yield of toria in eastern Himalayas.

Effect of phosphorus and biofertilizers on phosphorus use efficiency, biological N-Fixation and yield of pigeonpea (Cajanus cajan L.)

A field experiment was conducted during rainy seasons of 2013–14 and 2014–15 at the Rajola Krishi Research Farm, Faculty of Agricultural Sciences, Mahatma Gandhi Chitrakoot Gramodaya Vishwa Vidyalaya, Chitrakoot-Satna, Madhya Pradesh, India to study the effect of phosphorus and biofertilizers on phosphorus use efficiency (PUE) and biological N-fixation (BNF) yield of pigeonpea Qajanus cajan L.) variety UPAS-120. The agronomical and physiological PUE and its recovery were found significantly higher (10.40, 44.83 and 13.09 respectively) under the lowest level of phosphorus (P30). The reserve was true in case of P90. Dual biofertilizers (Rhizobium + PSB) gave significantly higher physiological PUE over single biofertilizer; where as agronomical PUE and recovery were found identical. Application of phosphorus up to 90 kg P2O5/ha gave maximum grain yield (16.06 q/ha). The dual biofertilizers also gave maximum yield up to 15.56 q/ha. The BNF was highest in these treatments. Hence the N-balance in soil was maximum (230 kg/ha).

Band-application of phosphorus with farm manure improves phosphorus use efficiency, productivity, and net returns of wheat on sandy clay loam soil

Phosphorus use efficiency (PUE) is very low in alkaline calcareous soils; however, it can be improved by using suitable application methods along with farm manure (FM). The present field study was conducted to optimize phosphorus (P) levels and application methods in order to maximize wheat yield, PUE, and net returns on calcareous soils with and without FM application. Five P soil solution levels, i.e. 0.00, 0.05, 0.10, 0.20, and 0.30 mg P L-1, were maintained according to the Freundlich model through the application of 0, 36, 61, 104, and 142 kg P2O5 ha-1, respectively. The calculated P (0, 36, 61, 104, and 142 kg P2O5 ha-1) was applied by broadcasting, band-placement, and top-dressing, with or without 300 kg ha-1 well-rotted FM. The results revealed that the band-placement technique at 104 kg P2O5 ha-1 improved PUE and wheat output with and without FM application. Furthermore, wheat grain and straw P uptake was high at 142 kg P2O5 ha-1. In addition, protein content and Olsen P were high at 142 kg P2O5 ha-1. The band-placement technique at 104 kg P2O5 ha-1 increased net returns and the cost/benefit ratio. FM application further augmented the productivity, PUE, and net returns under various P levels and application techniques. In conclusion, band-placement of P at 104 kg P2O5 ha-1 with FM improved yield, PUE, and net returns of wheat sown on sandy clay loam calcareous soils.

Screening of inbred popcorn lines for tolerance to low phosphorus.

Increasing phosphorus use efficiency in agriculture is essential for sustainable food production. Thus, the aims of this study were: i) to identify phosphorus use efficiency (PUE) in popcorn lines during the early plant stages, ii) to study the relationship between traits correlated with PUE, and iii) to analyze genetic diversity among lines. To accomplish this, 35 popcorn lines from Universidade Estadual de Maringá breeding program were studied. The experiment was conducted in a growth chamber using a nutrient solution containing two concentrations of phosphorus (P): 2.5 μM or low P (LP) and 250 μM or high P (HP). After 13 days in the nutrient solution, root morphology traits, shoot and root dry weight, and P content of the maize seedlings were measured. A deviance analysis showed there was a high level of genetic variability. An unweighted pair group method with arithmetic mean (UPGMA) clustering analysis identified three groups for the LP treatment (efficient, intermediate, and inefficient) and three groups for the HP treatment (responsive, moderately responsive, and unresponsive). The results of a principal component analysis and selection index were consistent with the UPGMA analysis, and lines 1, 2, 13, 17, 26, and 31 were classified as PUE.