Comparison on Responses of Different Phosphorus-Efficient Wheat Varieties to Phosphorus-Deficiency Stress

Six wheat (Triticum aestivum L.) varieties with different phosphorus (P) efficiency, selected according to their relative yield in P-deficient soil to that in P sufficient soil, were used to compare their responses to P deficiency in growth, root and shoot P content and P concentration in leaf phloem exudates in solution culture. Results showed that P deficiency repressed shoot growth, whereas stimulated root growth. Accordingly, root-shoot dry weight ratio of the P deficient plants was relatively larger than that of the P-sufficient plants. Comparing with P-inefficient varieties, the growth rate of shoot and roots of P-efficient varieties was relatively low both under P-sufficient and -deficient conditions. Phosphorus deficiency also resulted in decrease in shoot and root P content. The rate of decrease in shoot was faster than in root. Difference in P partitioning in shoot and root between P-efficient and -inefficient varieties could not be observed. However, a negative relationship between P concentration in leaf phloem exudates of nine-day-old seedlings of these wheat varieties and their degrees of P efficiency were found under the P-sufficient condition, with higher in P-inefficient varieties but lower in P-efficient varieties. The reduce rate of P concentration in leaf phloem exudates of P-efficient varieties was rather slower than that of P-inefficient varieties, showing higher relative P concentration in leaf phloem exudates. The relative P concentration in leaf phloem exudates under P deficiency ranged from 35.9% of the P-sufficient controls in P-inefficient varieties to 59.0% in P-efficient varieties on the 10th day after the treatments.

Diverse functions of GmNLA1 members in controlling phosphorus homeostasis highlight coordinate response of soybean to nitrogen and phosphorus availability

Nitrogen(N) and phosphorus(P) are two essential mineral nutrients for plant growth,which are required in relative high amount in plants.Plants have evolved a series of strategies for coordinately acquiring and utilizing N and P.However,physiological and molecular mechanisms underlying of N and P interactions remain largely unclear in soybean(Glycine max).In this study,interactions of N and P were demonstrated in soybean as reflected by significant increases of phosphate(Pi) concentration in both leaves and roots by N deficiency under Pi sufficient conditions.A total of four nitrogen limitation adaptation(NLA),encoding RING-type E3 ubiquitin ligase were subsequently identified in soybean genome.Among them,transcription of Gm NLA1-1 and Gm NLA1-3 was decreased in soybean by N starvation under Pi sufficient conditions,not for Gm NLA1-2.Suppression of all three Gm NLA1 members was able to increase Pi concentration regardless of the P and N availability in the growth medium,but decrease fresh weight under normal conditions in soybean hairy roots.However,comparted to changes in control lines at two N levels,N deficiency only resulted in a relatively higher increase of Pi concentration in Gm NLA1-1 or Gm NLA1-3 suppression lines,strongly indicating that Gm NLA1-1 and Gm NLA1-3 might regulate P homeostasis in soybean response to N starvation.Taken together,our result suggest that redundant and diverse functions present in Gm NLA1 members for soybean coordinate responses to P and N availability,which mediate P homeostasis.

Development of Root Phenotyping Platforms for Identification of Root Architecture Mutations in EMS-Induced and Low-Path-Sequenced Sorghum Mutant Population

Sorghum’s natural adaptation to a wide range of abiotic stresses provides diverse genetic reserves for potential improvement in crop stress tolerance. Growing interest in sorghum research has led to the expansion of genetic resources though establishment of the sorghum association panel (SAP), generation of mutagenized populations, and recombinant inbred line (RIL) populations, etc. Despite rapid improvement in biotechnological tools, lack of efficient phenotyping platforms remains one of the major obstacles in utilizing these genetic resources. Scarcity of efforts in root system phenotyping hinders identification and integration of the superior root traits advantageous to stress tolerance. Here, we explored multiple approaches in root phenotyping of an ethyl methanesulfonate (EMS)-mutagenized sorghum population. Paper-based growth pouches (PGP) and hydroponics were employed to analyze root system architecture (RSA) variations induced by mutations and to test root development flexibility in response to phosphorus deficiency in early growing stages. PGP method had improved capabilities compared to hydroponics providing inexpensive, space-saving, and high-throughput phenotyping of sorghum roots. Preliminary observation revealed distinct phenotypic variations which were qualitatively and quantitatively systemized for association analysis. Phenotypes/ideotypes with root architecture variations potentially correlated with Pi acquisition were selected to evaluate their contribution to P-efficiency (PE). Sand mixed with P-loaded activated alumina substrate (SAS) provided closely to natural but still controlled single-variable conditions with regulated Pi availability. Due to higher labor and cost input we propose SAS to be used for evaluating selected sorghum candidates for PE. The ability of rapidly screening root phenotypes holds great potential for discovering genes responsible for relevant root traits and utilizing mutations to improve nutrient efficiency and crop productivity.

Soil Fertility Survey in Western Usambara Mountains, Northern Tanzania

Soil samples from thirty sites representing four agro-ecological zones in the Western Usambara Mountains (WUM) of the Lushoto District in northern Tanzania were collected and analyzed for different nutrients. The results suggested that the major soil fertility constraint was P deficiency. On the basis of critical levels established in other areas, 90% of the soils were ranked as P deficient. This was followed by N, which was ranked as inadequate in 73% of the sites. Magnesium, K, and Ca also appeared limiting with 67%, 53% and 50% of the soils falling below the established critical values, respectively. A few soils (10%) were also found to contain exchangeable Al. The metallic micronutrients (Cu, Fe, and Zn) were adequate in all soils. Two sites had excessive Mn that could lead to toxicity in crops, and one was Mn deficient.

Genetic diversity for mycorrhizal symbiosis and phosphate transporters in rice

Phosphorus （P） is a major plant nutrient and developing crops with higher P-use efficiency is an important breeding goal. In this context we have conducted a comparative study of irrigated and rainfed rice varieties to assess genotypic differences in colonization with arbuscular mycorrhizal （AM） fungi and expression of different P trans- porter genes. Plants were grown in three different soil samples from a rice farm in the Philippines. The data show that AM symbiosis in all varieties was established after 4 weeks of growth under aerobic conditions and that, in soil derived from a rice paddy, natural AM populations recovered within 6 weeks. The analysis of AM marker genes （AM1, AM3, AM14） and P transporter genes for the direct Pi uptake （PT2, PT6） and AM-mediated pathway （PTll, PT13） were largely in agreement with the observed root AM colonization providing a useful tool for diversity studies. Interestingly, delayed AM colonization was observed in the aus-type rice varieties which might be due to their different root structure and might confer an advantage for weed competition in the field. The data further showed that P-starvation induced root growth and expression of the high-affinity P transporter PT6 was highest in the irrigated variety IR66 which a]so maintained grain yield under P-deficient field conditions.

Sex-specifically responsive strategies to phosphorus availability combined with different soil nitrogen forms in dioecious Populus cathayana

Aims Phosphorus(P)availability and efficiency are especially important for plant growth and productivity.However,the sex-specific P acquisition and utilization strategies of dioecious plant species under different N forms are not clear.Methods This study investigated the responsive mechanisms of dioecious Populus cathayana females and males based on P uptake and allocation to soil P supply under N deficiency,nitrate(NO3−)and ammonium(NH4+)supply.Important Findings Females had a greater biomass,root length density(RLD),specific root length(SRL)and shoot P concentration than males under normal P availability with two N supplies.NH4+supply led to higher total root length,RLD and SRL but lower root tip number than NO3−supply under normal P supply.Under P deficiency,males showed a smaller root system but greater photosynthetic P availability and higher leaf P remobilization,exhibiting a better capacity to adaptation to P deficiency than females.Under P deficiency,NO3−supply increased leaf photosynthesis and P use efficiency(PUE)but reduced RLD and SRL in females while males had higher leaf P redistribution and photosynthetic PUE than NH4+supply.Females had a better potentiality to cope with P deficiency under NO3−supply than NH4+supply;the contrary was true for males.These results suggest that females may devote to increase in P uptake and shoot P allocation under normal P availability,especially under NO3−supply,while males adopt more efficient resource use and P remobilization to maximum their tolerance to P deficiency.

Symbionts in Mucuna pruriens stimulate plant performance through nitrogen fixation and improved phosphorus acquisition

Aims South Africa is mainly dominated by savanna and grasslands ecosystems which have been previously reported to be acidic and nutrient deficient,specifically with regard to phosphorus(P)and nitrogen(N).Mucuna pruriens(L.)DC,commonly known as velvet bean,is an indigenous legume in most African countries and has been reported to withstand these adverse soil conditions.The legume is used in many countries of the world for their medicinal value as well as for soil fertilization purposes.Although there are reports on M.pruriens growth and establishment in nutrient stressed ecosystems,no investigation has been conducted on M.pruriens symbiotic interactions,N source preference and associated growth carbon costs when subjected to P deficiency.In this study,we determined the impact of microbial symbionts on N nutrition and growth carbon costs of M.pruriens under P deficiency.Methods Microbe inoculation soils were collected from four geographical distinct KwaZulu-Natal locations.Thereafter,seeds were germinated in these natural soils and in early stages of nodule development,then seedlings were transferred in sterile quartz sand and supplied with Long Ashton nutrient media with varying P concentrations.Important Findings The 16S RNA sequence results revealed that M.pruriens was nodulated by Burkholderia sp.,Paenibacillus sp.and Bacillus irrespective of P concentrations.Even though P deficiency resulted in decreased overall biomass/growth,the root biomass,nodule number and carbon costs increased.In addition,low P supplied saplings showed the highest arbuscular mycorrhiza fungi percentage root colonization.In M.pruriens,nitrogen derived from atmosphere had a positive correlation with P level and the saplings had a dual reliance on atmospheric derived N and soil derived N with increased reliance on soil N in low P supplied plants.Therefore,M.pruriens exhibited different morphological and microbial symbiosis when subjected to P deficiency.

Identify Non-mutational p53 Functional Deficiency in Human Cancers

An accurate assessment of p53's functional statuses is critical for cancer genomic medicine.However,there is a significant challenge in identifying tumors with non-mutational p53 inactivation which is not detectable through DNA sequencing.These undetected cases are often misclassified as p53-normal,leading to inaccurate prognosis and downstream association analyses.To address this issue,we built the support vector machine(SVM)models to systematically reassess p53's functional statuses in TP53 wild-type(TP53^(WT))tumors from multiple The Cancer Genome Atlas(TCGA)cohorts.Cross-validation demonstrated the good performance of the SVM models with a mean area under the receiver operating characteristic curve(AUROC)of 0.9822,precision of 0.9747,and recall of 0.9784.Our study revealed that a significant proportion(87%-99%)of TP53^(WT) tumors actually had compromised p53 function.Additional analyses uncovered that these genetically intact but functionally impaired(termed as predictively reduced function of p53 or TP53^(WT)-pRF)tumors exhibited genomic and pathophysiologic features akin to TP53-mutant tumors:heightened genomic instability and elevated levels of hypoxia.Clinically,patients with TP53^(WT)-pRF tumors experienced significantly shortened overall survival or progression-free survival compared to those with predictively normal function of p53(TP53^(WT)-pN)tumors,and these patients also displayed increased sensitivity to platinum-based chemotherapy and radiation therapy.

Effect of Biochar Addition on Maize Growth and Nitrogen Use Efficiency in Acidic Red Soils

Biochar added to soil can improve crop growth through both direct and indirect effects, particularly in acidic, highly weathered soils in subtropical and tropical regions. However, the mechanisms of biochar improving crop growth are not well understood. The objectives of this study were i) to determine the crop responses to biochar addition and ii) to understand the effect of biochar addition on N use efficiency. Seven acidic red soils varying in texture, p H, and soil nutrient were taken from southern China and subjected to four treatments: zero biochar and fertilizer as a control(CK), 10 g kg-1biochar(BC), NPK fertilizers(NPK), and 10 g kg-1biochar plus NPK fertilizers(BC+NPK).15N-labeled fertilizer was used as a tracer to assess N use efficiency. After a 46-d pot experiment,biochar addition increased soil p H and available P, and decreased soil exchangable Al3+, but did not impact soil availabe N and cation exchange capacity(P > 0.05). The N use efficiency and N retained in the soil were not significantly affected by biochar application except for the soil with the lowest available P(3.81 mg kg-1) and highest exchanageable Al3+(4.54 cmol kg-1). Greater maize biomass was observed in all soils amended with biochar compared to soils without biochar(BC vs. CK, BC+NPK vs. NPK). This agronomic effect was negatively related to the concentration of soil exchangeable Al3+(P < 0.1). The results of this study implied that the liming effect of biochar improved plant growth through alleviating Al toxicity and P deficiency, especially in poor acidic red soils.

Influence of Arbuscular Mycorrhizal Fungi on Growth, Mineral Nutrition and Chlorogenic Acid Content of Lonicera confusa Seedlings Under Field Conditions

Lonicera confusa, a traditional Chinese medicine herb for treating cold, flu, acute fever, and so forth, is often grown artificially in acidic soils and suffers from phosphorus (P) deficiency. A five-year field experiment was carried out to study the colonization rate, growth, nutrition, and chlorogenic acid content of Lonicera confusa seedlings inoculated with arbuscular mycorrhizal (AM) fungi, Glomus etunicatum and Glomus intraradices. Before transplanting into a field, both AM-inoculated and uninoculated control plants were cultured in nursery beds. In the plants inoculated with the AM fungi, the colonization rate decreased linearly with time and a greater decrease was observed in the plants inoculated with G. intraradices than with G. etunicatum, while the AM colonization increased from 0% to 12.1% in the uninoculated control plants 5 years after transplanting. Plant height, crown diameter, number of new branches, and flower yield increased significantly by AM inoculation as compared to the uninoculated control. Phosphorus concentrations in leaves and flowers increased, and plant uptake of nutrients, e.g., nitrogen (N), P, and potassium (K), was also enhanced significantly by AM inoculation. The Lonicera confusa seedlings had a better response to inoculation of G. intraradices than G. etunicatum in both growth and chlorogenic acid content in flowers. In contrast, both plant P uptake and P concentrations in leaves and flowers were similar between two fungal inoculations. The positive responses of Lonicera confusa to AM inoculation in growth, nutrient uptake, flowering, and chlorogenic acid content in flowers suggested that AM inoculation in nursery beds could promote the plant growth and increase chlorogenic acid content in flowers of Lonicera confusa when grown on acidic and P-deficient soils.