Phosphorus deficiency affects multiple macromolecular biosynthesis pathways of Thalassiosira weissflogii

Phosphorus（P） is one of the key nutrients for the growth of phytoplankton. In this study, we used a method coupling label-free quantitation with liquid chromatography–mass spectrometry（LFQ–LC–MS/MS） to track the change of relative protein abundance between P-replete and P-deficient treatments in a non-model diatom, Thalassiosira weissflogii. Out of the 631 proteins identified, 132 were found to have significant changes in abundance（〉1.5 folds） between the two treatments, especially those proteins involved in macromolecular biosynthesis pathways. For example, the up-regulation of sulfolipid biosynthesis protein in the P-deficient culture suggested a switch from using phospholipids to sulfolipids. In addition, the ribosome subunits and tRNA synthetases were down-regulated, which might explain the decrease in protein content in the P-deficient culture. A vacuolar sorting receptor homologous protein was found to be 9.2-folds up-regulated under P-deficiency, indicating an enhancement in the vacuolar sorting pathway for protein degradation. Our results show that T. weissflogii has sophisticated responses in multiple macromolecular metabolism pathways under P-deficiency, a mechanism which can be critical for this species to survive under various levels of P availability in the environment

Effect of Phosphorus Deficiency on Leaf Photosynthesis and Carbohydrates Partitioning in Two Rice Genotypes with Contrasting Low Phosphorus Susceptibility

To study the effect of phosphorus （P） deficiency on leaf photosynthesis and carbohydrates partitioning and to determine whether the characteristics of leaf photosynthesis and carbohydrates partitioning are related to low P tolerance in rice plants, a hydroponic culture experiment supplied with either sufficient P （10 mg/L） or deficient P （0.5 mg/L） was conducted by using two rice genotypes different in their responses to low P stress. Results showed that the plant growth of Zhenongda 454 （low P tolerant genotype） was less affected by P deficiency compared with Sanyang＇ai （low P sensitive genotype）. Under P-deficient conditions, photosynthetic rates of Zhenongda 454 and Sanyang＇ai were decreased by 16% and 35%, respectively, and Zhenongda 454 showed higher photosynthetic rate than Sanyang＇ai. Phosphorus deficiency decreased the stomatal conductance for both genotypes, but had no significant influence on leaf internal CO2 concentration （Ci）, suggesting that the decrease in leaf photosynthetic rate of rice plants induced by P deficiency was not due to stomatal limitation. Phosphorus deficiency increased the concentration of soluble carbohydrates and sucrose in shoots and roots for both genotypes, and also markedly increased the allocation of soluble carbohydrates and sucrose to roots. Under deficient P supply, Zhenongda 454 had higher root/shoot soluble carbohydrates content ratio and root/shoot sucrose content ratio than Sanyang＇ai. In addition, phosphorus deficiency increased the concentration of starch in roots for both genotypes, whereas had no effect on the content of starch in shoots or roots. Compared to genotype Sanyang＇ai, the better tolerance to low-P stress of Zhenongda 454 can be explained by the fact that Zhenongda 454 maintains a higher photosynthetic rate and a greater ability to allocate carbohydrates to the roots under P deficiency.

A mitochondrial phosphate transporter,McPht gene,confers an acclimation regulation of the transgenic rice to phosphorus deficiency

Phosphate transporters play an important role in promoting the uptake and transport of phosphate in plants. In this study, the McPht gene from the Mesembryanthemum crystallinum, a mitochondrial phosphate transporter, was isolated and constructed onto a constitutive expression vector carrying 35S：：GFP, and the recombinant constructs were transferred into Oryza sativajaponica L. cv. Kitaake to investigate the regulatory role of the McPhtgene under phosphorus deficiency. The McPhtgene encodes a protein of 357 amino acids with six transmembrane domains and is located to the mitochondria, and the mRNAtranscripts of the McPht gene are highly accumulated in the shoots of M. crystallinum in response to phosphorus deficiency. However, more mRNA transcripts of the McPht gene were accumulated in the roots of the transgenic rice under phosphorus deficiency. Measurements showed that the transgenic rice demonstrated an enhanced promotion in the root development, the root activities, and phosphate uptake under phosphorus deficiency. Transcriptome sequencing showed that the transgenic rice exhibited total of 198 differentially expressed genes. Of these, total of 154 differentially expressed genes were up-regulated and total 44 genes were down-regulated comparing to the wild type in response to phosphorus deficiency. The selective six genes of the up-regulated differentially expressed genes showed an enhanced increase in mRNA transcripts in response to phosphorus deficiency, however, the transcripts of the mitochondrial carrier protein transporter in rice, a homologous gene of the McPht, in both the transgenic line and the wild type had no obvious differences. Functional enrichment analyses revealed that the most of the up-regulated genes are involved in the cytoplasmic membrane-bounded vesicle, and most of the down-regulated genes are involved in the mitochondrion and cytoplasmic membrane-bounded vesicle. The differentially expressed genes were highly enriched in plant secondary metabolisms and plant-pathogen interaction. These results indicated that the overexpression of the McPht gene might participate in the physiological adaptive modulation of the transgenic rice to phosphorus deficiency by up- or down-regulating the differentially expressed genes.

Molecular cytogenetic characterization of a novel wheat-Thinopyrum intermedium introgression line tolerant to phosphorus deficiency

Thinopyrum intermedium has been used as a resource for improving resistance to biotic and abiotic stresses and yield potential in common wheat. Wheat line SN304 was derived from a cross between common wheat cultivar Yannong 15 and Th. intermedium. Genomic in situ hybridization(GISH) produced no hybridization signal in SN304 using Th. intermedium genomic DNA as a probe, but fluorescence in situ hybridization(FISH) using oligonucleotides AFA-3, AFA-4, pAs1-1, pAs1-3, pAs1-4, pAs1-6, pSc119.2-1,and(GAA)10 as probes detected hybridization signals on chromosomes 2 A, 7 A, 2 B, 3 B, 6 B, and 7 B in SN304 that differed from Yannong 15. Results of specific markers also indicated that there were Th. intermedium chromatin introgressions on different chromosomes in SN304. In a hydroponic culture experiment, SN304 not only produced more biomass and higher stem and leaf dry weight but also accumulated more phosphorus than Yannong 15 under phosphorus-deficiency stress. Moreover, SN304 produced a lower pH and released more organic acids, especially oxalic acid, than Yannong 15, which suggests that SN304 exudates enabled more absorbance of P than Yannong 15 under comparable conditions.The results indicate that SN304 is a wheat-Th. intermedium introgression line with tolerance to phosphorus-deficiency stress.

Involvement of Antioxidative Defense System in Rice Seedlings Exposed to Aluminum Toxicity and Phosphorus Deficiency

Plants growing in acid soils may suffer both phosphorus （P） deficiency and aluminum （Al） toxicity.Hydroponic experiments were undertaken to assess the single and combination effects of Al toxicity and low P stress on seedling growth,chlorophyll and proline contents,antioxidative response and lipid peroxidation of two rice genotypes （Yongyou 8 and Xiushui 132） differing in Al tolerance.Al toxicity and P deficiency both inhibited rice seedling growth.The development of toxic symptoms was characterized by reduced chlorophyll content,increased proline and malondialdehyde contents in both roots and leaves,and increased peroxidase and superoxide dismutase activities in roots,but decreased in leaves.The stress condition induced more severe growth inhibition and oxidative stress in Yongyou 8,and Xiushui 132 showed higher tolerance to both Al toxicity and P deficiency.P deficiency aggravated Al toxicity to plant growth and induced more severe lipid peroxidation.

Physiological and molecular responses of invasive cyanobacterium Raphidiopsis raciborskii to ambient phosphorus deficiency

Raphidiopsis raciborskii can cause harmful cyanobacterial blooms when concentrations of environme ntal pho sphorus(P)are very low,thus the physiological and molecular mechanisms involved in the acclimation to P need to be characterized better.The growth,chlorophyll fluorescence,alkaline phosphatase,and expression of genes directly involved in P assimilation were compared in the R.raciborskii FACHB1496 strain grown with and without inorganic P.The specific growth rate(μ),Chl a,and six fluorescence parameters(minimal fluorescence(F),maximal fluorescence(F),maximal variable fluorescence(F),electron transport flux(further than QA)per RC(ET/RC),quantum yield of the electron transport in PSⅡ(?),and the probability that an electron from a trapped exciton is moved into the electron transport chain beyond Q~-(Ψ))markedly decreased in R.raciborskii in response to experimental P-deficiency.In contrast,the relative variable fluorescence at the J-step(V),trapped energy flux(leading to QA reduction)per RC(TR/RC),and alkaline phosphatase activity significantly increased.In addition,gene expressions involved in the alkaline phosphatase(phoAl and phoA2),high-affinity inorganic P transporter(pstSl),phosphonate transporter and metabolism(phnD and phnM),and nucleotidase(nucH)were significantly upregulated under P deficiency.However,physiological and molecular responses were resumed rapidly after P re-supplementation following P-deficient conditions.Our results highlight that R.raciborskii can perform coordinated and complex cellular and physiological responses to cope with P deficiency,reflecting R.raciborskii’s multi-faceted machinery to respond to environmental P fluctuations.

Effect of dietary calcium or phosphorus deficiency on bone development and related calcium or phosphorus metabolic utilization parameters of broilers from 22 to 42 days of age

This experiment was conducted to investigate the effect of dietary calcium(Ca)or phosphorus(P)deficiency on bone development and related Ca or P metabolic utilization parameters of broilers from 22 to 42 days of age based on our previous study,which indicated that dietary Ca or P deficiency impaired the bone development by regulating related Ca or P metabolic utilization parameters of broilers from 1 to 21 days of age.A total of 504 one-day-old Arbor Acres male broilers were randomly assigned to 1 of 4 treatments with 7 replicates in a completely randomized design,and fed the normal control and Ca-or P-deficient diets from 1 to 21 days of age.At 22 days of age,the broilers were further fed the normal control diet(0.90%Ca+0.35%non-phytate P(NPP)),the P-deficient diet(0.90%Ca+0.18%NPP),the Ca-deficient diet(0.30%Ca+0.35%NPP)or the Ca and P-deficient diet(0.30%Ca+0.18%NPP),respectively.The results showed that dietary Ca or P deficiency decreased(P<0.05)tibia bone mineral density(BMD),bone breaking strength(BBS),ash content,tibia ash Ca content and serum P content on days 28 and 42,but increased(P<0.05)tibia alkaline phosphatase(ALP)activity of broilers on day 42 compared with the control group.Furthermore,the broilers fed the P-deficient diet had the lowest(P<0.05)tibia BMD,BBS,ash content,serum P content and the highest(P<0.05)serum Ca content on day 28 compared with those fed the Ca-deficient or Ca and P-deficient diets.The results from the present study indicated that the bone development and related Ca or P metabolic utilization parameters of broilers were the most sensitive to dietary P deficiency,followed by dietary Ca deficiency or Ca and P-deficiency;dietary Ca or P deficiency impaired the bone development possibly by regulating serum Ca and P contents as well as tibia Ca content and ALP activity of broilers from 22 to 42 days of age.

Responses of Legumes to Phosphorus Deficiency

Phosphorus deficiency is a universal problem in most world soils. Furthermore, of all nutrients, shortage of phosphorus has the biggest impact on legumes, therefore, lots of studies were carried out for identifying responses of legumes to shortage of phosphorus. They concluded that to maintain improved growth under phosphorus defioiency oonditions plants develop two major mechanisms： （i） Phosphorus acquisition （root morphology, root exudation and phosphorus uptake mechanisms）, （ii） Phosphorus utilization （internal mechanisms associated with better use of absorbed phosphorus at cellular level）. The aim of this brief review is to elucidate root morphological ohanges and rhizophere aoidification to phosphorus deficiency.

Small RNA Profiling Reveals Phosphorus Deficiency as a Contributing Factor in Symptom Expression for Citrus Huanglongbing Disease

Huanglongbing （HLB） is a devastating citrus disease that is associated with bacteria of the genus ＇Candidatus Liberibacter＇ （Ca. L.）. Powerful diagnostic tools and management strategies are desired to control HLB. Host small RNAs （sRNA） play a vital role in regulating host responses to pathogen infection and are used as early diagnostic markers for many human diseases, including cancers. To determine whether citrus sRNAs regulate host responses to HLB, sRNAs were profiled from Citrus sinensis 10 and 14 weeks post grafting with Ca. L. asiaticus （Las）-positive or healthy tissue. Ten new microRNAs （miRNAs）, 76 conserved miRNAs, and many small interfering RNAs （siRNAs） were discovered. Several miRNAs and siRNAs were highly induced by Las infection, and can be potentially developed into early diagnosis markers of HLB. miR399, which is induced by phosphorus starvation in other plant species, was induced specifically by infection of Las but not Spiroplasma citri that causes citrus stubborn--a disease with symptoms similar to HLB. We found a 35% reduction of phosphorus in Las-positive citrus trees compared to healthy trees. Applying phosphorus oxyanion solutions to HLB-positive sweet orange trees reduced HLB symptom severity and significantly improved fruit production during a 3-year field trial in south-west Florida. Our molecular, physiological, and field data suggest that phosphorus deficiency is linked to HLB disease symptomology.

Aerenchyma Formed Under Phosphorus Deficiency Contributes to the Reduced Root Hydraulic Conductivity in Maize Roots

Root hydraulic conductivity has been shown to decrease under phosphorus （P） deficiency. This study Investigated how the formation of aerenchyma is related to this change. Root anatomy, as well as root hydraulic conductivity was studied In maize （Zea mays L.） roots under different phosphorus nutrition conditions. Plant roots under P stress showed enhanced degradation of cortical cells and the aerenchyma formation was associated with their reduced root hydraulic conductivity, supporting our hypothesis that air spaces that form in the cortex of phosphorusstressed roots Impede the radial transport of water in a root cylinder. Further evidence came from the variation In aerenchyma formation due to genotypic differences. Five maize inbred lines with different porosity in their root cortex showed a significant negative correlation with their root hydraulic conductivity. Shoot relative water content was also found lower In P-deficient maize plants than that in P-sufficient ones when such treatment was prolonged enough, suggesting a limitation of water transport due to lowered root hydraulic conductivity of P-deficient plants.

NaCl Facilitates Cell Wall Phosphorus Reutilization in Abscisic Acid Dependent Manner in Phosphorus Deficient Rice Root

Phosphorus(P) starvation in rice facilitates the reutilization of root cell wall P by enhancing the pectin content. NaCl modulates pectin content, however, it is still unknown whether NaCl is also involved in the process of pectin regulated cell wall P remobilization in rice under P starved conditions. In this study, we found that 10 mmol/L NaCl increased the shoot and root biomasses under P deficiency to a remarkable extent, in company with the elevated shoot and root soluble P contents in rice. Further analysis indicated that exogenous NaCl enhanced the root cell wall P mobilization by increasing the pectin methylesterase activity and uronic acid content in pectin suggesting the involvement of NaCl in the process of cell wall P reutilization in P starved rice roots. Additionally, exogenous NaCl up-regulated the expression of P transporter OsPT6, which was induced by P deficiency, suggesting that NaCl also facilitated the P translocation prominently from root to shoot in P starved rice. Moreover, exogenous abscisic acid(ABA) can reverse the NaCl-mediated mitigation under P deficiency, indicating the involvement of ABA in the NaCl regulated root cell wall P reutilization. Taken together, our results demonstrated that NaCl can activate the reutilization of root cell wall P in P starved rice, which is dependent on the ABA accumulation pathway.

Phosphorus Starvation Tolerance in Rice Through Combined Physiological,Biochemical,and Proteome Analyses

Phosphorus(P) deficiency limits the growth,development,and productivity of rice.To better understand the underlying mechanisms in P-deficiency tolerance and the role of Pup1 QTL in enhancing P use efficiency(PUE) for the development of P-efficient rice cultivars,a pair of contrasting rice genotypes(Pusa-44 and NIL-23) was applied to investigate the morpho-physio-biochemical and proteomic variation under P-starvation stress.The rice genotypes were grown hydroponically in a PusaRich medium with adequate P(16 mg/kg,+P) or without P(0 mg/kg,-P) for 30 d.P-starvation manifested a significant reductions in root and shoot biomass,shoot length,leaf area,total chlorophyll,and P,nitrogen and starch contents,as well as protein kinase activity.The stress increased root-to-shoot biomass ratio,root length,sucrose content,and acid phosphatase activity,particularly in the P-tolerant genotype(NIL-23).Comparative proteome analysis revealed several P metabolism-associated proteins(including OsCDPKs,OsMAPKs,OsCPKs,OsLecRK2,and OsSAPks) to be expressed in the shoot of NIL-23,indicating that multiple protein kinases were involved in P-starvation/deficiency tolerance.Moreover,the up-regulated expression of OsrbcL,OsABCG32,OsSUS5,OsPoll-like B,and ClpC2 proteins in the shoot,and OsACA9,OsACA8,OsSPS2F,OsPP2C15,and OsBiP3 in the root of NIL-23,indicated their role in P-starvation stress control through the Pup1 QTL. Thus,our findings indicated that-P stress-responsive proteins,in conjunction with morpho-physio-biochemical modulations,improved PUE and made NIL-23 a P-deficiency tolerant genotype due to the introgression of the Pup1 QTL in the Pusa-44 background.

Genetic improvement of legume roots for adaption to acid soils

Acid soils occupy approximately 50% of potentially arable lands.Improving crop productivity in acid soils,therefore,will be crucial for ensuring food security and agricultural sustainability.High soil acidity often coexists with phosphorus(P) deficiency and aluminum(Al) toxicity,a combination that severely impedes crop growth and yield across wide areas.As roots explore soil for the nutrients and water required for plant growth and development,they also sense and respond to below-ground stresses.Within the terrestrial context of widespread P deficiency and Al toxicity pressures,plants,particularly roots,have evolved a variety of mechanisms for adapting to these stresses.As legumes,soybean(Glycine max) plants may acquire nitrogen(N) through symbiotic nitrogen fixation(SNF),an adaptation that can be useful for mitigating excessive N fertilizer use,either directly as leguminous crop participants in rotation and intercropping systems,or secondarily as green manure cover crops.In this review,we investigate legumes,especially soybean,for recent advances in our understanding of root-based mechanisms linked with root architecture modification,exudation and symbiosis,together with associated genetic and molecular strategies in adaptation to individual and/or interacting P and Al conditions in acid soils.We propose that breeding legume cultivars with superior nutrient efficiency and/or Al tolerance traits through genetic selection might become a potentially powerful strategy for producing crop varieties capable of maintaining or improving yields in more stressful soil conditions subjected to increasingly challenging environmental conditions.

Aetiology and Pathogenesis Studies on Osteoporosis in Bactrian Camel

A disease characterized by emaciation, pica, lameness and liability to fracture in bactrian camel from gravel desert pasture was described. Analyses of mineral elements in soil, water and forage from the affected and normal areas as well as in blood, hair and parts of tissues from normal and diseased camel, together with a pathological study were carried out to define the nature and major causes of the disease. The related blood indices were also measured. The result indicated that copper and phosphorus in the soil and forage from the affected area were significantly lower than those of the normal area (P<0.01). The levels of phosphorus in the blood, hair and rib reduced significantly in affected camels. The concentrations of PTH, T3, T4, creat-inine(Crt) and the activities of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) in serum rose markedly (P<0.01). Bone injury was characterized by osteoporosis. The degenerative and necrotic lesions of liver and kidney were common. In addition, slight demylination of brains and spinal cords were showed by histopathological and ultrastructural studies. It is concluded that the disease is caused mainly by phosphorus deficiency in the food chain.

Effects of low pH and aluminum stresses on common beans (Phaseolus vulgaris) differing in low-phosphorus and photoperiod responses

Using common beans differing greatly in the response to photoperiod and low-phosphorus(P)stress,we investigated their responses to acidity and aluminum(Al)toxicity and the relationship between Al tolerance and organic acid exudation under Al or low P stress.A genotype Ginshi was found to be sensitive to low pH treatment.When exposed to pH 4.5,serious curvature in the root tips of cv.Ginshi was observed;however,it was completely corrected by the application of 5 or 10μmol/L AlCl 3;increasing calcium(Ca)could ameliorate Al toxicity,but it could not correct root curvature at pH 4.5.Common beans showed significant differences in both root growth and Al tolerance,and the varieties from the Andes were more tolerant to Al toxicity than those from the Mesoamerican origin.In the presence of 50μmol/L AlCl 3,all the common bean genotypes exuded citrate,and a significant difference in the amounts of citrate was observed among genotypes.The genotypes originated in the Mesoamerica tended to release more citrate than other origins in the presence of Al.The P-inefficient genotype DOR364 exuded more citrate than the P-efficient genotype G19833 in the presence of 50μmol/L AlCl 3,whereas no organic acids were detected in root exudates under low-P stress.A reduction of citrate exudation in the DOR364,but a slight increase of citrate exudation in the G19833,was observed under Al stress after they were exposed to 6-d P starvation.These results suggest that different low-P or Al tolerance in common beans might not be associated with organic acid exudation.

Molecular mechanisms of plant adaptation to acid soils: A review

Acid soils are widespread and limit global plant production.Aluminum(Al)/manganese(Mn)toxicity and phosphorus(P)deficiency are the major limiting factors affecting plant growth and productivity on acid soils.Plants,however,have evolved various strategies to adapt to these stresses.These strategies include using both external and internal mechanisms to adapt to Al toxicity,regulating Mn uptake,translocation,and distribution to avoid Mn toxicity,and orchestrating a set of P transport mechanisms to efficiently take up P from the soil.Here,we review the current state of knowledge about the molecular mechanisms of plant adaptation to these constraints in acid soils,focusing on the roles of transporters involved in Al/Mn tolerance and P efficiency.Gene manipulation combined with other biotechnology will contribute to the development of novel strategies to improve plant adaptation to acid soils.The molecular mechanisms of plant coadaptation to multiple stresses in acid soils are largely unknown and require further investigation.