Deficiency Stress Research Articles

Adaptive strategies to minimise iron limiting stress under climate change scenario: A study pertinent to iron stress response of two soybean (Glycine max (L.) Merr.) Genotypes

The response of soybean genotypes to iron deficiency stress under elevated CO2 and temperature condition could be guided by three critical rhizospheric processes viz. proton (H+) extrusion, root exudation and ferric chelate reductase (FCR) activity. In the present study, the iron efficient and responsive (FeER) genotype recorded an impressive performance over iron inefficient and responsive (FeIR) genotype in counteracting iron deficiency stress but experienced modest stress caused by the combined interaction between the genotype (G), environment (E) and HCO3- ion (B). The antagonistic interaction between Fe2+ with HCO3- ion resulted in greater iron stress. Plants grown in the absence of bicarbonate have significantly higher total chlorophyll content (1.79±0.04 mg g-1, mean ± SE) than plants grown in presence of bicarbonate (1.48 ± 0.06 mg g-1). To warfare the constraints in Fe availability, especially under more stressed e-[CO2+T] environmental condition in the presence of bicarbonate ion, the root system of iron efficient genotype of soybean (FeER) exuded out significantly higher amount of low molecular weight organic acids. Furthermore, the presence of bicarbonate ion in the nutrient solution exacerbated the iron deficiency stress and consequently resulted in higher proton extrusion (~1.2 fold increase), lower ferric chelate reductase activity (~1.3 fold decrease) and higher organic acid exudation (up to ~1.9 fold increase in malic acid). The intra-specific variability between contrasting genotypes and their response to elevated CO2 and temperature could be exploited to remediate emerging Fe deficiency of soybean plants under climate change scenario.

Nitrogen application save phosphorus deficiency in maize inbred line QXH0121

Nitrogen and phosphorus dual stress significantly inhibited the maize growth and decreased the accumulation of nitrogen and phosphorus in plants. The co-application of nitrogen and phosphorus most significantly increased the biomass compared to the dual deficiency stress, and to our surprise, the repair effect of nitrogen application alone was basically similar to the repair effect of simultaneous application of nitrogen and phosphorus reflected in biomass as well as nitrogen and phosphorus content. Transcriptomic analysis showed that DEGs related to phosphorus transporters in N versus NP group and N versus P group were all up-regulated. These all confirm that the nitrogen application alone mitigated damages caused by low nitrogen and phosphorus dual stress comparable to that of nitrogen and phosphorus co-application. These indicate that the presence of nitrogen is conducive to the accumulation and transportation of phosphorus.

Cloning and functional analysis of ZIP transporters in blueberry

Blueberry (Vaccinium spp., Vc) plants are highly susceptible to Fe deficiency stress. An understanding of the mechanisms involved in Fe as well as other mineral ions uptake and transportation is critical for the improvement of mineral ions use efficiency in the field practices. The functional roles of the VcZIPs in mineral ions uptake and transportation were not well understood. To elucidate the functions of ZIP transporter family that is involved in the uptake and transport of metal elements in blueberry, VcZIPs such as VcZIP1, VcZIP2, VcZIP6, VcZIP7, VcZIP8 and VcZIP11 were cloned and identified from blueberry genome. The results of functional complementarity and heterologous expression of yeast mutant verified that most of VcZIPs had the ability to transport Fe and Zn, and VcZIP1 and VcZIP7 could mediate the transport of Cd in yeast. Furthermore, higher chlorophyll contents and bigger crown diameter sizes were observed in VcZIP6, VcZIP7 and VcZIP8 over-expressed Arabidopsis thaliana at Fe deficient treatments. In this study, VcZIP1, VcZIP2, VcZIP6–VcZIP8 and VcZIP11 were Fe-deficient responsive genes in blueberry. VcZIP6–VcZIP8 participated in the uptake of Fe and likely contributed to Fe uptake and transportation in plants. VcZIP1, VcZIP7, VcZIP8 and VcZIP11 were involved transportation Zn in blueberry. Comparatively, higher Zn-transport abilities were observed in VcZIP1 and VcZIP7.

Genome-wide characterization and expression analysis of HAK K+ transport family in Ipomoea.

The online version contains supplementary material available at 10.1007/s13205-020-02552-3.

Foliar exposure of zinc oxide nanoparticles improved the growth of wheat (Triticum aestivum L.) and decreased cadmium concentration in grains under simultaneous Cd and water deficient stress

A pot study was conducted to explore the effectiveness of zinc oxide nanoparticles (ZnO NPs) foliar exposure on growth and development of wheat, zinc (Zn) and cadmium (Cd) uptake in Cd-contaminated soil under various moisture conditions. Four different levels (0, 25, 50, 100 mg/L) of these NPs were foliar-applied at different time periods during the growth of wheat. Two soil moisture regimes (70% and 35% of water holding capacity) were maintained from 6 weeks of germination till plant harvesting. The results revealed that the growth of wheat increased with ZnO NPs treatments. The best results were found in 100 mg/L ZnO NPs under normal moisture level. The lowest Cd and highest Zn concentrations were also examined when 100 mg/L NPs were applied without water deficit stress. In grain, Cd concentrations decreased by 26%, 81% and 87% in normal moisture while in water deficit conditions, the Cd concentrations decreased by 35%, 66% and 81% compared to control treatment when ZnO NPs were used at 25, 50 and 100 mg/L. The foliar exposure of ZnO NPs boosted up the leaf chlorophyll contents and also decreased the oxidative stress and enhanced the leaf superoxide dismutase and peroxidase activities than the control. It can be suggested that foliar use of ZnO NPs might be an efficient way for increasing wheat growth and yield with maximum Zn and minimum Cd contents under drought stress while decreasing the chances of NPs movement to other environmental compartment which may be possible in soil applied NPs.

MxMPK6-2-bHLH104 interaction is involved in reactive oxygen species signaling in response to iron deficiency in apple rootstock.

Iron (Fe) is a trace element necessary for plant growth. Many land plants have evolved a set of mechanisms associated with the Fe absorption process to deal with the problem of insufficient Fe supply in the soil. During Fe absorption, reactive oxygen species (ROS) can be used as a signal to initiate a response to stress caused by Fe deficiency. However, the molecular mechanisms underlying the involvement of ROS in the Fe deficiency stress response remains unclear. In this study, we have identified a kinase, MxMPK6-2, from Malus xiaojinensis, an apple rootstock that is highly efficient at Fe absorption. MxMPK6-2 has been shown to be responsive to ROS signals during Fe deficiency, and MxMPK6-2 overexpression in apple calli enhanced its tolerance to Fe deficiency. We further screened for proteins in the Fe absorption pathway and identified MxbHLH104, a transcription factor which interacts with MxMPK6-2. MxbHLH104 can be phosphorylated by MxMPK6-2 in vivo, and we confirmed that its phosphorylation increased Fe absorption in apple calli under Fe deficiency, with the presence of ROS promoting this process. Overall, we have demonstrated that MxMPK6-2 is responsive to ROS signaling during Fe deficiency, and is able to control its response by regulating MxbHLH104.

Identification of Shaker K+ channel family members in sweetpotato and functional exploration of IbAKT1.

The Shaker K+ channel family plays a vital role in potassium absorption and stress resistance in plants. However little information on the genes family is available about sweetpotato. In the present study, eleven sweetpotato Shaker K+ channel genes were identified and classified into five groups based on phylogenetic relationships, conserved motifs, and gene structure analyses. Based on synteny analysis, four duplicated gene pairs were identified, derived from both ancient and recent duplication, whereas only one resulted from tandem duplication events. Different expression pattern of Shaker K+ channel genes in roots of Xu32 and NZ1 resulted in different K+ deficiency tolerances, suggesting there is different mechanism of K+ uptake in sweetpotato cultivars with different K+-tolerance levels. Quantitative real-time PCR analysis revealed that the shaker K+ channel genes responded to drought and high salt stresses. Higher K+ influx under normal condition and lower K+ efflux under K+ deficiency stress were observed in IbAKT1 overexpressing transgenic roots than in adventitious roots, which indicated that IbAKT1 may play an important role in the regulation of K+ deficiency tolerance in sweetpotato. This is the first genome-wide analysis of Shaker K+ channel genes and the first functional analysis of IbAKT1 in sweetpotato. Our results provide valuable information on the gene structure, evolution, expression and functions of the Shaker K+ channel gene family in sweetpotato.

Managing Sphincter Deficiency Stress Urinary Incontinence in the Neurogenic Patient: Diagnosis and Management Strategies

In this review, we present the current literature on the diagnosis and management of stress urinary incontinence induced by sphincter deficiency associated with neurogenic lower urinary tract dysfunction. Because sphincter deficiency stress urinary incontinence is not a common condition, there are no guidelines or large-scale clinical studies that focus on the diagnosis and management of this condition. Although there is consensus that urodynamic investigation is the only method to assess the function of the lower urinary tract, there is no established urodynamic criteria to diagnose neurogenic sphincter deficiency. As for the treatment of sphincter deficiency stress urinary incontinence in neurogenic patients, artificial urinary sphincter has a better success rate and a higher complication and reoperation rate than other methods including sling surgery and injection of bulking agents. Although there is a progress in the evaluation and management of neurogenic patients with sphincter deficiency stress urinary incontinence, a prospective multicenter clinical study on this condition should be highly recommended.

Lolium perenne'de Fosfat Eksikliği Stresinde miRNA408’in Rolü: Üç Yıllık Tarla Çalışması

Fosfat eksikliği, bitkilerde büyüme ve gelişmeyi sınırlandıran bir stres faktörüdür. Fosfat eksikliği koşullarında bitkiler birtakım moleküler stratejiler geliştirmiştir. miRNA (miR)'lar, genleri susturarak bitkilerdeki stres mekanizmaları gibi ana süreçlerin düzenleyicisi olarak karakterize edilirler. miR408, sınırlı sayıda bitkide fosfat eksikliğine karşı role sahiptir. Bugüne kadar Lolium perenne (çok yıllık çim) bitkisinde fosfat eksikliği mekanizmasında yer alan miR'ler yeterince açıklanmamıştır. Bu çalışmanın amacı, miR408 ekspresyonunun çok yıllık çim bitkisinde varlığını doğrulamak ve tarla koşullarında fosfat eksikliği stresine karşı önemli bir rol oynayıp oynamadığını belirlemektir. Çalışmada altı adet çok yıllık çim populasyonunun fosfat eksikliği stresine karşı duyarlılıkları (kuru ot verimi ve kalite özellikleri) üç yıllık tarla çalışması ile belirlenmiştir. Tarla çalışmalarından elde edilen sonuçlar kuru ot verimi ve kalite özelliklerindeki düşüşlerin, fosfat eksikliği stresine karşı diğerlerine (P2 ve P3,) kıyasla P1 ve P4 populasyonları için daha az olduğunu ortaya koymuştur. Moleküler analiz sonuçları dikkate alındığında, fosfat eksikliği stresi altında P1 ve P4 populasyonlarında miR408'in ekspresyon seviyesinde önemli artış gözlemlenirken, P2 ve P3’te herhangi bir değişiklik tespit edilmemiştir. Elde edilen sonuç miR408'in çok yıllık çim bitkisinde fosfat eksikliği stresine toleranstan sorumlu olabileceğini göstermektedir. Bu miR, fosfat eksikliğine karşı dayanıklı çok yıllık çim bitkisi geliştirme amaçlı kullanım potansiyeline sahiptir.

MiR168 targets Argonaute1A mediated miRNAs regulation pathways in response to potassium deficiency stress in tomato

BackgroundPotassium (K+) is an essential ion for most plants, as it is involved in the regulation of growth and development. K+ homeostasis in plant cells has evolved to facilitate plant adaptation to K+-deficiency stress. Argonaute1 (AGO1) is regulated by miR168 to modulate the small RNA regulatory pathway by RNA silencing complex (RISC) in tomatoes. However, the role of miR168-mediated regulation of AGO1 in the context of K+ deficiency stress in tomatoes has not been elucidated yet.ResultsSlmiR168 and its target gene SlAGO1A were differentially expressed among low-K+-tolerant JZ34 and low-K+-sensitive JZ18 tomato plants. Transgenic tomato plants constitutively expressing pri-SlmiR168a showed stronger root system growth, better leaves development, and higher K+ contents in roots under K+-deficiency stress than those of the transgenic tomato lines expressing rSlAGO1A (SlmiR168-resistant) and the wild type (WT). Deep sequencing analysis showed that 62 known microRNAs (miRNAs) were up-regulated in 35S:rSlAGO1 compared with WT tomatoes. The same miRNAs were down-regulated in 35S:SlmiR168a compared with WT plants. The integrated analysis found 12 miRNA/mRNA pairs from the 62 miRNAs, including the root growth and cytokinin (CTK)/abscisic acid (ABA) pathways.ConclusionsThe regulation mediated by SlmiR168 of SlAGO1A contributes to the plant development under low-K+ stress. Moreover, this regulation mechanism may influence downstream miRNA pathways in response to low-K+ stress through the CTK/ABA and root growth modulation pathways.

Poultry Litter Biochar Increases Mycorrhizal Colonisation, Soil Fertility and Cucumber Yield in a Fertigation System on Sandy Soil

There is a continuing argument about the benefits of biochar on arbuscular mycorrhizal (AM) symbiosis, crop growth, yield, and fertility of soil. There is also limited research on the effects of biochar on AM colonization, cucumber yield, and soil fertility improvement. Therefore, this investigation aimed to determine the impact of poultry litter biochar (PLB) on colonization of roots by indigenous AM fungi in agricultural soil and their contribution to cucumber yield, nutrition, and soil fertility improvement. A field trial was conducted to assess the effect of PLB combined with compound poultry manure (CPM) and nitrophos (NP) fertilizer to investigate the response of treatments on nutrient-deficient sandy soils. Plant growth responses to biochar showed better plant growth and yield of cucumber. Application of biochar with and without CPM and NP reduced the negative impact of nutrient deficiency stress on cucumber growth. AM fungal colonization, soil fertility, and cucumber yield were improved with the combined application of biochar, CPM, and NP fertilizer. Post-harvest, soil C, N, P, K, Ca, Mg, S, Zn, Cu, Fe, and Mn increased with application of biochar applied with CPM and NP. Biochar application with CPM and NP also increased the percent root colonization of cucumber. Use of biochar with CPM and NP has the potential to improve plant growth, yield, nutrient uptake, and soil fertility. Further studies in various agro-ecological conditions would help utilize this technology in sustainable crop production.

Genome-wide identification and analysis of high-affinity nitrate transporter 2 (NRT2) family genes in rapeseed (Brassica napus L.) and their responses to various stresses

BackgroundHigh-affinity nitrate transporter 2 (NRT2) genes have been implicated in nitrate absorption and remobilization under nitrogen (N) starvation stress in many plant species, yet little is known about this gene family respond to various stresses often occurs in the production of rapeseed (Brassica napus L.).ResultsThis report details identification of 17 NRT2 gene family members in rapeseed, as well as, assessment of their expression profiles using RNA-seq analysis and qRT-PCR assays. In this study, all BnNRT2.1 members, BnNRT2.2a and BnNRT2.4a were specifically expressed in root tissues, while BnNRT2.7a and BnNRT2.7b were mainly expressed in aerial parts, including as the predominantly expressed NRT2 genes detected in seeds. This pattern of shoot NRT expression, along with homology to an Arabidopsis NRT expressed in seeds, strongly suggests that both BnNRT2.7 genes play roles in seed nitrate accumulation. Another rapeseed NRT, BnNRT2.5 s, exhibited intermediate expression, with transcripts detected in both shoot and root tissues. Functionality of BnNRT2s genes was further outlined by testing for adaptive responses in expression to exposure to a series of environmental stresses, including N, phosphorus (P) or potassium (K) deficiency, waterlogging and drought. In these tests, most NRT2 gene members were up-regulated by N starvation and restricted by the other stresses tested herein. In contrast to this overall trend, transcription of BnNRT2.1a was up-regulated under waterlogging and K deficiency stress, and BnNRT2.5 s was up-regulated in roots subjected to waterlogging. Furthermore, the mRNA levels of BnNRT2.7 s were enhanced under both waterlogging stress and P or K deficiency conditions. These results suggest that these three BnNRT2 genes might participate in crosstalk among different stress response pathways.ConclusionsThe results presented here outline a diverse set of NRT2 genes present in the rapeseed genome that collectively carry out specific functions throughout rapeseed development, while also responding not just to N deficiency, but also to several other stresses. Targeting of individual BnNRT2 members that coordinate rapeseed nitrate uptake and transport in response to cues from multiple stress response pathways could significantly expand the genetic resources available for improving rapeseed resistance to environmental stresses.

The versatile role of glucose signalling in regulating growth, development and stress responses in plants

Sugars as an energy source and a signalling molecule are indispensible for growth, development and stress responses in plants. Among sugars, glucose (Glc) has been identified to perform a key role in regulating various cellular and developmental processes in plants. This comprehensive review highlights the crosstalk of glucose signalling with auxin, cytokinin and brassinosteroid signalling in controlling several aspects of plant development including root growth deviation, root waving and coiling, lateral root emergence, hypocotyl elongation, etc. through a Hexokinase 1 dependent and independent pathway in Arabidopsis. It also provides an insight on the role of Glc-mediated target of rapamycin signalling in modulating various abiotic stresses like nutrient deficiency stress, heat stress, oxidative stress etc. The review also discusses about sugar inducible FCS-Like Zinc Finger genes in modulating SNF1-related protein kinase 1 signalling to coordinate growth and stress responses in plants. Therefore, glucose signalling in concert with diverse signalling pathways and via regulating certain genes contributes to numerous cellular processes to control development and stress responses in plants.

Mitigating the Harmful Effects of Water Deficiency Stress on White Lupine (Lupinus albus L.) Plants by Using Algae Extract and Hydrogen Peroxide. تخفیف الآثار الضارة الناتجة عن اجهاد نقص المیاه على نباتات الترمس الأبیض باستخدام مستخلص الطحالب وفوق اکسید الهیدروجین.

Water deficit is a major growth limitation factor affecting plant growth and productivity. To counteract the harmful effects of drought stress, lupine plants were sprayed with two concentrations of algae extract (1 g L-1 and 2 g L-1) and hydrogen peroxide solution (0.5% and 1%) under low irrigation level. Morphological, physiological and anatomical studies were performed. It was found that all treatments enhanced plant height, root length, number of leaves, average leaf area, shoot and root fresh and dry weights. A significant increment in chlorophyll a and b, carotenoids and total pigments contents, as well as a significant decrease in electrolyte leakage was noted in treated plants compared with untreated under water deficit. Increment in levels of osmoprotectants such as proline, total free amino acids, glycine betaine and total soluble sugars contents was highly significant in case of 2 g L-1 algae extract treatment compared with untreated plants group. Anatomical studies of root, stem and leaf of treated and untreated plants revealed that 2 g L-1 algae extract treatment followed with 0.5% H2O2 induced significant increments in the thickness of the studied plant organs compared with the untreated plants under water deficit conditions. In general, the concentrations of 2 g L-1 algae extract and 0.5% H2O2 were the most effective doses regarding all the studied characteristics.

Function and application of the Eutrema salsugineum PHT1;1 gene in phosphate deficiency stress.

Low availability of inorganic phosphate (Pi) in soil is often a limiting factor for plant growth and productivity. The Pi transporter plays an important role in the absorption and utilization of phosphorus in plants. Eutrema salsugineum shows strong tolerance under Pi stress conditions, but the function of the E. salsugineum PHT1 genes has not yet been systematically studied. This study isolated a phosphate transporter gene (EsPHT1;1) from the halophyte E. salsugineum and functionally characterized it in the herbaceous model plant, Arabidopsis thaliana, and in an important oil crop species, soybean (Glycine max (L.) Merr.). Under Pi deficient conditions, transgenic Arabidopsis and transgenic soybean grew better and exhibited significant improvement in root growth, biomass accumulation and seed yield compared with wild-type (WT) plants. These phenotypic enhancements were more apparent under inadequate Pi conditions than under sufficient or no Pi conditions, which is in agreement with the observation that the transgenic plants accumulated higher amounts of Pi and total P in shoots and roots than WT plants only when inadequate Pi was supplied. The results of the present study indicate that overexpression of EsPHT1;1 can efficiently enhance the growth and reproductive performance of both Arabidopsis and soybean plants challenged by low P stress, which results confirm the important role of PHT1;1 in dealing with Pi deficiency.

SINAT E3 ligases regulate the stability of the ESCRT component FREE1 in response to iron deficiency in plants.

The endosomal sorting complex required for transport (ESCRT) machinery is an ancient, evolutionarily conserved membrane remodeling complex that is essential for multivesicular body (MVB) biogenesis in eukaryotes. FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING 1 (FREE1), which was previously identified as a plant-specific ESCRT component, modulates MVB-mediated endosomal sorting and autophagic degradation. Although the basic cellular functions of FREE1 as an ESCRT component have been described, the regulators that control FREE1 turnover remain unknown. Here, we analyzed how FREE1 homeostasis is mediated by the RING-finger E3 ubiquitin ligases, SINA of Arabidopsis thaliana (SINATs), in response to iron deficiency. Under iron-deficient growth conditions, SINAT1-4 were induced and ubiquitinated FREE1, thereby promoting its degradation and relieving the repressive effect of FREE1 on iron absorption. By contrast, SINAT5, another SINAT member that lacks ubiquitin ligase activity due to the absence of the RING domain, functions as a protector protein which stabilizes FREE1. Collectively, our findings uncover a hitherto unknown mechanism of homeostatic regulation of FREE1, and demonstrate a unique regulatory SINAT-FREE1 module that subtly regulates plant response to iron deficiency stress.

AZ-97 (Oryza sativa ssp. Indica) exhibits superior biomass production by maintaining the tiller numbers, leaf width, and leaf elongation rate under phosphorus deficiency

ABSTRACT Shoot morphology in rice plants changes in response to P deficiency. However, how genotypic variations in these morphological changes affect the canopy development and biomass production have hardly been explored. The study aimed to identify specific shoot morphological traits that confer biomass production under P deficiency. Four rice genotypes, including AZ-97 (WAS 63–22-5-9-10-1), which exhibits high performance under highly P-deficient fields in Madagascar, were grown for 56 days in flooded pots over several P application rates to simulate P-sufficient and moderately, severely, and extremely P-deficient conditions. AZ-97 had superior shoot P contents and biomass than Takanari, a high-yielding cultivar, and X265, a common high-yielding cultivar in Madagascar at severely to moderately P-deficient conditions. Shoot biomass was highly correlated with projected leaf area (PLA) from the early growth stage, and tiller number, leaf width, and leaf elongation rate explained the variations in PLA. These morphological traits reduced significantly with decreased P application rates, while reduction in AZ-97 was small relative to the other genotypes, even for equivalent shoot P contents. As the result, AZ-97 had greater PLA per unit of shoot P content at equivalent shoot P contents. The result indicates that lower sensitivity and degrees of change in shoot morphology when exposed to P deficiency stress could be a key trait facilitating the maintenance of captured radiation and subsequently influencing genotypic differences in external P uptakes and biomass production. AZ-97 is a potential donor with such traits that can offer an additional avenue for genetic improvement toward P-efficient rice production.Abbreviations DAT: days after transplanting; LN: leaf number in the main stem; PLA: projected green leaf area; PUE: phosphorus use efficiency; SSA: Sub-Saharan Africa.

Estimation of maize properties and differentiating moisture and nitrogen deficiency stress via ground – Based remotely sensed data

Moisture and nitrogen deficiency are major determinant factors for cereal production in arid and semi arid environments. The ability to detect stress in crops at an early stage is crucially important if significant reductions in yield are to be averted. In this context, remotely sensed data has the possibility of providing a rapid and accurate tool for site specific management in cereal crop production. This research examined the potential of hyperspectral and broad band remote sensing for predicting maize properties under nitrogen and moisture induced stress. Spectra were collected from drip irrigated maize subjected to various rates of irrigation regimes and nitrogen fertilization. 60 spectral vegetation indices were derived and examined to predict maize yield and other properties. Highly significant correlations between maize crop properties and various vegetation indices were noticed. RVI and NDVI were found to be sensitive to maize grain yield in both tested seasons. Cred edge demonstrated the strongest significant correlations with maize yield. The correlations with grain yield were found to be strongest at the flowering stage. Penalized linear discriminant analysis (PLDA) showed the possibility to distinguish moisture and nitrogen deficiency stress spectrally. The implications of this work for the use of satellite based remote sensing in arid zone precision agriculture are discussed.

Genetic variation associated with the shoot biomass of upland cotton seedlings under contrasting phosphate supplies

As over-fertilization leads to environmental concerns, selecting cultivars that can produce high yields on phosphorus (P)-deficient soils and understanding the genetic basis underlying P-starved tolerance have become crucially important. In this study, we evaluated the variation of ten P deficiency-related traits at the seedling stage of 419 core accessions in two different environments. The results showed that the shoot dry weight (SDW) could be considered an indicator for screening P-tolerant germplasm resources. A genome-wide association study (GWAS) was performed for two SDW-related traits using 3.66 million high-quality single-nucleotide polymorphisms (SNPs). A total of 102 significantly associated SNPs were located within or near 137 genes, of which, 27 of the SNPs were consistently detected for multiple traits or multiple environments. We further identified and validated a novel candidate gene, Gh_D11G2219, by qRT-PCR analysis and virus-induced gene silencing (VIGS), and the results suggested that Gh_D11G2219 plays a role in the positive regulation of tolerance to P deficiency stress in cotton. In addition, the elite SNPs linked to tolerance to P-starved stress have undergone negative selection pressure during the cotton breeding process. This is the first GWAS of P deficiency tolerance, and the identified SNPs and candidate genes provide valuable information for breeding highly P-efficient varieties.

The Ca2+ -regulated protein kinase CIPK1 integrates plant responses to phosphate deficiency in Arabidopsis thaliana.

Phosphate (Pi) deficiency severely restricts plant growth and development, as Pi is an essential macronutrient. Calcium (Ca2+ ) is a ubiquitous second messenger in plants; calcineurin B-like proteins (CBL) and CBL-interacting protein kinases (CIPK) are signalling pathways that act as an important Ca2+ signalling network which integrates plants to fine tune the response to stress; however, whether CIPK are involved in Pi deficiency stress remains largely unknown. In this study, we carried out a reverse genetic strategy to screen T-DNA insertion mutants of CIPK isoforms under Pi deficiency in Arabidopsis thaliana. Then Pi content, transcription of phosphate starvation-induced (PSI) genes, acid phosphatase activity and hydrogen peroxide were determined in the wild-type (WT) and cipk1 mutant, respectively. The phenotype of CIPK1 complementation lines was analysed. The cipk1 mutant had a more sensitive phenotype, with lower root elongation and root length, and decreased Pi content compared with the WT under Pi deficiency. Moreover, CIPK1 mutation caused phosphate starvation-induced (PSI) genes to be significantly induced under Pi deficiency. Histological staining demonstrated that the cipk1 mutant had increased acid phosphatase activity and hydrogen peroxide concentration under Pi deficiency. By using the yeast two-hybrid system, we further demonstrated the interaction between CIPK1 and the WRKY transcription factors, WRKY6 and WRKY42. Overall, we demonstrate that CIPK1 is involved in the Pi deficiency signalling pathway in A. thaliana, revealing the important role of Ca2+ in the Pi nutrition signalling pathway, and potentially providing a theoretical foundation for molecular breeding of crops with better Pi utilization efficiency.