Dynamic Changes in Distribution of Lignin and Hemicelluloses in Cell Walls During Differentiation of Secondary Xylem in Eucommia ulmoides

The dynamic changes in the distribution of lignin and hemicelluloses (xylans and xyloglucans) in cell walls during the differentiation of secondary xylem in Eucommia ulmoides Oliv. were studied by means of ultraviolet light microscopy and transmission electron microscopy combined with immunogold labelling. In the cambial zone and cell expansion zone, xyloglucans were localized both in the tangential and radial walls, but no xylans or lignin were found in these regions. With the formation of secondary wall S-1 layer, lignin occurred in the cell corners and middle lamella, while xylans appeared in S-1 layer, and xyloglucans were localized in the primary walls and middle lamella. In pace with the formation of secondary wall S-2 and S-3 layer, lignification extended to S-1, S-2 and S-3 layer in sequence, showing a patchy style of lignin deposition. Concurrently, xylans distributed in the whole secondary walls and xyloglucans, on the other hand, still localized in the primary walls and middle lamella. The results indicated that along with the formation and lignification of the secondary wall, great changes had taken place in the cell walls. Different parts of cell walls, such as cell corners, middle lamella, primary walls and various layers of secondary walls, had different kinds of hemicelluloses, which formed various cell wall architecture combined with lignin and other cell wall components.

Mechanical characterization of Pinus massoniana cell walls infected by blue-stain fungi using in situ nanoindentation

Characterizing the mechanical properties of wood cell walls will lead to better understanding and optimization of modifications made to wood infected by the blue-stain fungi.In this study,in situ nanoindentation was used to characterize the mechanical properties of the cell walls of Pinus massoniana infected by blue-stain fungi at the cellular level.The results show that in situ nanoindentation is an effective method for this purpose and that blue-stain fungi penetrate wood structures and degrade wood cell walls,significantly reducing the mechanical properties of the cell walls.The method can also be used to evaluate and improve the properties of other wood species infected by blue-stain fungi.

Humans have intestinal bacteria that degrade the plant cell walls in herbivores

The cell walls of plants are mainly made of cellulose and contain a large number of calories.However,the main component,cellulose,is an indigestible plant fiber that is thought to be difficult for humans to use as energy.Herbivores acquire energy through the degradation of cell wall-derived dietary fiber by microorganisms in the digestive tract.Herbivores,especially horses,have a highly developed cecum and large intestine,and plants are fermented for their efficient use with the help of microorganisms.Humans also have an intestinal tract with a wide lumen on the proximal side of the large intestine,in which fermentation occurs.The digestive process of horses is similar to that of humans,and many of the intestinal bacteria found in horses that degrade plants are also found in humans.Therefore,it is thought that humans also obtain a certain amount of energy from cell wall-derived dietary fiber.However,the intake of dietary fiber by modern humans is low;thus,the amount of calories derived from indigestible plant fiber is considered to be very low.Cellulose in the plant cell wall is often accompanied by hemicellulose,pectin,lignin,suberin,and other materials.These materials are hard to degrade,and cellulose is therefore difficult for animals to utilize.If the cell wall can be degraded to some extent by cooking,it is thought that humans can obtain calories from cell wall-derived dietary fiber.If humans can use the calories from the cell wall for their diet,it may compensate for human food shortages.

BRITTLE CULM16(BRITTLE NODE) is required for the formation of secondary cell walls in rice nodes

Plant cell walls constitute the skeletal structures of plant bodies,and thus confer lodging resistance for grain crops.While the basic cell wall synthesis machinery is relatively well established now,our understanding of how the process is regulated remains limited and fragmented.In this study,we report the identification and characterization of the novel rice（Oryza sativa L.）brittle culm16（brittle node;bc16）mutant.The brittle node phenotype of the bc16 mutant appears exclusively at nodes,and resembles the previously reported bc5 mutant.Combined histochemical staining and electron microscopy assays revealed that in the bc16 mutant,the secondary cell wall formation and thickening of node sclerenchyma tissues are seriously affected after heading.Furthermore,cell wall composition assays revealed that the bc16 mutation led to a significant reduction in cellulose and lignin contents.Using a map-based cloning approach,the bc16 locus is mapped to an approximately 1.7-Mb region of chromosome 4.Together,our findings strengthen evidence for discretely spatial differences in the secondary cell wall formation within plant bodies.

Intratree Variation in Viscoelastic Properties of Cell Walls of Masson Pine (Pinus Massoniana Lamb)

In this study,Pinus massoniana Lamb at different heights,across the annual rings,and between earlywood and latewood was measured by X-ray diffraction and the chemical composition was analyzed by chemical treatment.Results indicated that the microfibril angle(MFA)decreased and the chemical composition changed little with the increase in height from 1 m to 9 m.In the radial direction,the MFA decreased and the chemical composition changed little with an increase in annual rings.The cellulose content of latewood was higher than that of early-wood.The viscoelastic changes of wood cell walls at different heights,across the annual rings by the method of quasi-static nanoindentation and dynamic modulus mapping techniques.Results indicated that the wood cell walls’elastic modulus increased,and the creep rate and creep compliance decreased with the increase in height;The elastic modulus and hardness increased with the annual rings.The cell walls’storage modulus increased and the loss modulus gradually decreased with an increase in height;the storage modulus gradually increased and the loss modulus decreased with the annual rings.

Observations of Wood Cell Walls with a Scanning Probe Microscope

Scanning Probe Microscopes (SPMs) observe specimen surfaces with probes by detecting the physical amount of a material between the cantilever and the surface. SPMs have a high resolution and can measure mechanical characteristics such as stiffness, adsorptive properties, and viscoelasticity. These features make it easy to identify the surface structure of complex materials;therefore, the use of SPMs has increased in recent years. Wood cell walls are primarily composed of cellulose, hemicellulose, and lignin. It is believed that hemicellulose and lignin surround the cellulose framework;however, their detailed formation remains unknown. Therefore, we observed wood cell walls via scanning probe microscopy to try to reveal the formation of the cellulose framework. We determined that the size of the cellulose microfibril bundle and hemicellulose lignin module composite was 18.48 nm based on topography and that the size of the cellulose microfibril bundle was 15.33 nm based on phase images. In the viscoelasticity image, we found that the viscoelasticities of each cell wall of the same cell were not the same. This is because the cellulose microfibrils in each cell wall lean in different directions. The angle between the leaning of the cellulose microfibril and the cantilever affects the viscoelasticity measurement.

Woody plant cell walls:Fundamentals and utilization

Cell walls in plants,particularly forest trees,are the major carbon sink of the terrestrial ecosystem.Chemical and biosynthetic features of plant cell walls were revealed early on,focusing mostly on herbaceous model species.Recent developments in genomics,transcriptomics,epigenomics,transgenesis,and associated analytical techniques are enabling novel insights into formation of woody cell walls.Here,we review multilevel regulation of cell wall biosynthesis in forest tree species.We highlight current approaches to engineering cell walls as potential feedstock for materials and energy and survey reported field tests of such engineered transgenic trees.We outline opportunities and challenges in future research to better understand cell type biogenesis for more efficient wood cell wall modification and utilization for biomaterials or for enhanced carbon capture and storage.

Pectin methylesterase inhibitors GhPMEI53 and AtPMEI19 improve seed germination by modulating cell wall plasticity in cotton and Arabidopsis

The germination process of seeds is influenced by the interplay between two opposing factors,pectin methylesterase(PME)and pectin methylesterase inhibitor(PMEI),which collectively regulate patterns of pectin methylesterification.Despite the recognized importance of pectin methylesterification in seed germination,the specific mechanisms that govern this process remain unclear.In this study,we demonstrated that the overexpression of GhPMEI53is associated with a decrease in PME activity and an increase in pectin methylesterification.This leads to seed cell wall softening,which positively regulates cotton seed germination.AtPMEI19,the homologue in Arabidopsis thaliana,plays a similar role in seed germination to GhPMEI53,indicating a conserved function and mechanism of PMEI in seed germination regulation.Further studies revealed that GhPMEI53 and AtPMEI19 directly contribute to promoting radicle protrusion and seed germination by inducing cell wall softening and reducing mechanical strength.Additionally,the pathways of abscicic acid(ABA)and gibberellin(GA)in the transgenic materials showed significant changes,suggesting that GhPMEI53/AtPMEI19-mediated pectin methylesterification serves as a regulatory signal for the related phytohormones involved in seed germination.In summary,GhPMEI53 and its homologs alter the mechanical properties of cell walls,which influence the mechanical resistance of the endosperm or testa.Moreover,they impact cellular phytohormone pathways(e.g.,ABA and GA)to regulate seed germination.These findings enhance our understanding of pectin methylesterification in cellular morphological dynamics and signaling transduction,and contribute to a more comprehensive understanding of the PME/PMEI gene superfamily in plants.

Strigolactones modulate cotton fiber elongation and secondary cell wall thickening

Cotton is one of the most important economic crops in the world,and it is a major source of fiber in the textile industry.Strigolactones(SLs)are a class of carotenoid-derived plant hormones involved in many processes of plant growth and development,although the functions of SL in fiber development remain largely unknown.Here,we found that the endogenous SLs were significantly higher in fibers at 20 days post-anthesis(DPA).Exogenous SLs significantly increased fiber length and cell wall thickness.Furthermore,we cloned three key SL biosynthetic genes,namely GhD27,GhMAX3,and GhMAX4,which were highly expressed in fibers,and subcellular localization analyses revealed that GhD27,GhMAX3,and GhMAX4 were localized in the chloroplast.The exogenous expression of GhD27,GhMAX3,and GhMAX4 complemented the physiological phenotypes of d27,max3,and max4 mutations in Arabidopsis,respectively.Knockdown of GhD27,GhMAX3,and GhMAX4 in cotton resulted in increased numbers of axillary buds and leaves,reduced fiber length,and significantly reduced fiber thickness.These findings revealed that SLs participate in plant growth,fiber elongation,and secondary cell wall formation in cotton.These results provide new and effective genetic resources for improving cotton fiber yield and plant architecture.

Leaf Morphology Genes SRL1 and RENL1 Co-Regulate Cellulose Synthesis and Affect Rice Drought Tolerance

The morphological development of rice(Oryza sativa L.)leaves is closely related to plant architecture,physiological activities,and resistance.However,it is unclear whether there is a co-regulatory relationship between the morphological development of leaves and adaptation to drought environment.In this study,a drought-sensitive,roll-enhanced,and narrow-leaf mutant(renl1)was induced from a semi-rolled leaf mutant(srl1)by ethyl methane sulfonate(EMS),which was obtained from Nipponbare(NPB)through EMS.Map-based cloning and functional validation showed that RENL1 encodes a cellulose synthase,allelic to NRL1/OsCLSD4.The RENL1 mutation resulted in reduced vascular bundles,vesicular cells,cellulose,and hemicellulose contents in cell walls,diminishing the water-holding capacity of leaves.In addition,the root system of the renl1 mutant was poorly developed and its ability to scavenge reactive oxygen species(ROS)was decreased,leading to an increase in ROS after drought stress.Meanwhile,genetic results showed that RENL1 and SRL1 synergistically regulated cell wall components.Our results revealed a theoretical basis for further elucidating the molecular regulation mechanism of cellulose on rice drought tolerance,and provided a new genetic resource for enhancing the synergistic regulation network of plant type and stress resistance,thereby realizing simultaneous improvement of multiple traits in rice.

Upregulation of the glycine-rich protein-encoding gene GhGRPL enhances plant tolerance to abiotic and biotic stressors by promoting secondary cell wall development

Abiotic and biotic stressors adversely affect plant survival,biomass generation,and crop yields.As the global availability of arable land declines and the impacts of global warming intensify,such stressors may have increasingly pronounced effects on agricultural productivity.Currently,researchers face the overarching challenge of comprehensively enhancing plant resilience to abiotic and biotic stressors.The secondary cell wall plays a crucial role in bolstering the stress resistance of plants.To increase plant resistance to stress through genetic manipulation of the secondary cell wall,we cloned a cell wall protein designated glycine-rich protein-like(GhGRPL)from cotton fibers,and found that it is specifically expressed during the period of secondary cell wall biosynthesis.Notably,this protein differs from its Arabidopsis homolog,AtGRP,since its glycine-rich domain is deficient in glycine residues.GhGRPL is involved in secondary cell wall deposition.Upregulation of GhGRPL enhances lignin accumulation and,consequently,the thickness of the secondary cell walls,thereby increasing the plant’s resistance to abiotic stressors,such as drought and salinity,and biotic threats,including Verticillium dahliae infection.Conversely,interference with GhGRPL expression in cotton reduces lignin accumulation and compromises that resistance.Taken together,our findings elucidate the role of GhGRPL in regulating secondary cell wall development through its influence on lignin deposition,which,in turn,reinforces cell wall robustness and impermeability.These findings highlight the promising near-future prospect of adopting GhGRPL as a viable,effective approach for enhancing plant resilience to abiotic and biotic stress factors.

Arabidopsis thaliana T-DNA Mutants Implicate GAUT Genes in the Biosynthesis of Pectin and Xylan in Cell Walls and Seed Testa

Galacturonosyltransferase 1 （GAUT1） is an α1,4-D-galacturonosyltransferase that transfers galacturonic acid from uridine 5＇-diphosphogalacturonic acid onto the pectic polysaccharide homogalacturonan （Sterling et al., 2006）. The 25-member Arabidopsis thaliana GAUT1-related gene family encodes 15 GAUT and 10 GAUT-like （GATL） proteins with, respectively, 56-84 and 42-53% amino acid sequence similarity to GAUT1. Previous phylogenetic analyses of AtGAUTs indicated three clades： A through C. A comparative phylogenetic analysis of the Arabidopsis, poplar and rice GAUT families has sub-classified the GAUTs into seven clades： clade A-1 （GAUTs 1 to 3）; A-2 （GAUT4）; A-3 （GAUTs 5 and 6）; A-4 （GAUT7）; B-1 （GAUTs 8 and 9）; B-2 （GAUTs 10 and 11）; and clade C （GAUTs 12 to 15）. The Arabidopsis GAUTs have a distribution comparable to the poplar orthologs, with the exception of GAUT2, which is absent in poplar. Rice, however, has no orthologs of GAUTs 2 and 12 and has multiple apparent orthologs of GAUTs 1, 4, and 7 compared with eitherArabidopsis or poplar. The cell wall glycosyl residue compositions of 26 homozygous T-DNA insertion mutants for 13 of 15 Arabidopsis GAUTgenes reveal significantly and reproducibly different cell walls in specific tissues of gaut mutants 6, 8, 9, 10, 11, 12, 13, and 14 from that of wild-type Arabidopsis walls. Pectin and xylan polysaccharides are affected by the loss of GAUT function, as demonstrated by the altered galacturonic acid, xylose, rhamnose, galactose, and arabinose composition of distinct gaut mutant walls. The wall glycosyl residue compositional phenotypes observed among the gaut mutants suggest that at least six different biosynthetic linkages in pectins and/or xylans are affected by the lesions in these GAUTgenes. Evidence is also presented to support a role for GAUT11 in seed mucilage expansion and in seed wall and mucilage composition.

Identification of Lignin and Polysaccharide Modifications in Populus Wood by Chemometric Analysis of 2D NMR Spectra from Dissolved Cell Walls

2D ^13C-^1H HSQC NMR spectroscopy of acetylated cell walls in solution gives a detailed fingerprint that can be used to assess the chemical composition of the complete wall without extensive degradation. We demonstrate how multivariate analysis of such spectra can be used to visualize cell wall changes between sample types as high-resolution 2D NMR loading spectra. Changes in composition and structure for both lignin and polysaccharides can subsequently be interpreted on a molecular level. The multivariate approach alleviates problems associated with peak picking of overlapping peaks, and it allows the deduction of the relative importance of each peak for sample discrimination. As a first proof of concept, we compare Populus tension wood to normal wood. All well established differences in cellulose, hemicellulose, and lignin compositions between these wood types were readily detected, confirming the reliability of the multivariate approach, In a second example, wood from transgenic Populus modified in their degree of pectin methylesterification was compared to that of wild-type trees. We show that differences in both lignin and polysaccharide composition that are difficult to detect with traditional spectral analysis and that could not be a priori predicted were revealed by the multivariate approach. 2D NMR of dissolved cell wall samples combined with multivariate analysis constitutes a novel approach in cell wall analysis and provides a new tool that will benefit cell wall research.

Hetero-trans-β-Glucanase Produces Cellulose-Xyloglucan Covalent Bonds in the Cell Walls of Structural Plant Tissues and Is Stimulated by Expansin

Current cell-wall models assume no covalent bonding between cellulose and hemicelluloses such as xyloglu-can or mixed-linkageβ-D-glucan(MLG).However,Equisetum hetero-trans-β-glucanase(HTG)grafts cellu-lose onto xyloglucan oligosaccharides(XGOs)-and,we now show,xyloglucan polysaccharide-in vitro,thus exhibiting CXE(cellulose:xyloglucan endotransglucosylase)activity.In addition,HTG also catalyzes MLG-to-XGO bonding(MXE activity).In this study,we explored the CXE action of HTG in native plant cell walls and tested whether expansin exposes cellulose to HTG by disrupting hydrogen bonds.To quantify and visu-alize CXE and MXE action,we assayed the sequential release of HTG products from cell walls pre-labeled with substrate mimics.We demonstrated covalent cellulose--xyloglucan bonding in plant cell walls and showed that CXE and MXE action was up to 15%and 60%of total transglucanase action,respectively,and peaked in aging,strengthening tissues:CXE in xylem and cells bordering intercellular canals and MXE in scleren-chyma.Recombinant bacterial expansin(EXLX1)strongly augmented CXE activity in vitro.CXE and MXE ac-tion in living Equisetum structural tissues potentially strengthens stems,while expansin might augment the HTG-catalyzed CXE reaction,thereby allowing efficient CXE action in muro.Our methods will enable surveys for comparable reactions throughout the plant kingdom.Furthermore,engineering similar hetero-polymer formation into angiosperm crop plants may improve certain agronomic traits such as lodging tolerance.

Protecting Cell Walls from Binding Aluminum by Organic Acids Contributes to Aluminum Resistance

Aluminum-induced secretion of organic acids from the root apex has been demonstrated to be one major AI resistance mechanism in plants. However, whether the organic acid concentration is high enough to detoxify AI in the growth medium is frequently questioned. The genotypes of AI-resistant wheat, Cassia tora L. and buckwheat secrete malate, citrate and oxalate, respectively. In the present study we found that at a 35% inhibition of root elongation, the AI activities in the solution were 10, 20, and 50 μM with the corresponding malate, citrate, and oxalate exudation at the rates of 15, 20 and 21 nmol/cm2 per 12 h, respectively, for the above three plant species. When exogenous organic acids were added to ameliorate AI toxicity, twofold and eightfold higher oxalate and malate concentrations were required to produce the equal effect by citrate. After the root apical cell walls were isolated and preincubated in 1 mM malate, oxalate or citrate solution overnight, the total amount of AI adsorbed to the cell walls all decreased significantly to a similar level, implying that these organic acids own an equal ability to protect the cell walls from binding AI. These findings suggest that protection of cell walls from binding AI by organic acids may contribute significantly to AI resistance.

Dietary fiber in plant cell walls-the healthy carbohydrates

Dietary fiber(DF)is one of the major classes of nutrients for humans.It is widely distributed in the edible parts of natural plants,with the cell wall being the main DF-containing structure.DF content varies significantly in different plant species and organs,and the processing procedure can have a dramatic effect on the DF composition of plant-based foods.Given the considerable nutritional value of DF,a deeper understanding of DF in food plants,including its composition and biosynthesis,is fundamental to the establishment of a daily intake reference of DF and is also critical to molecular breeding programs for modifying DF content.In the past decades,plant cell wall biology has seen dramatic progress,and such knowledge is of great potential to be translated into DF-related food science research and may provide future research directions for improving the health benefits of food crops.In this review,to spark interdisciplinary discussions between food science researchers and plant cell wall biologists,we focus on a specific category of DF--cell wall carbohydrates.We first summarize the content and composition of carbohydrate DF in various plant-based foods,and then discuss the structure and biosynthesis mechanism of each carbohydrate DF category,in particular the respective biosynthetic enzymes.Health impacts of DF are highlighted,and finally,future directions of DF research are also briefly outlined.

Comparison of cell wall changes of two different types of apple cultivars during fruit development and ripening

Fruit development and ripening is a complex procedure(Malus×domestica Borkh.)and can be caused by various factors such as cell structure,cell wall components,and cell wall hydrolytic enzymes.In our study,we focused on the variations in fruit firmness,cell wall morphology and components,the activity of cell wall hydrolytic enzymes and the expression patterns of associated genes during fruit development in two different types of apple cultivars,the hard-crisp cultivar and the loose-crisp cultivar.In this paper,the aim was to find out the causes of the texture variations between the different type cultivars.Cell wall materials(CWMs),hemicellulose and cellulose content were strongly associated with variations in fruit firmness during the fruit development.The content of water soluble pectin(WSP)and chelator soluble pectin(CSP)gradually increased,while the content of ionic soluble pectin(ISP)showed inconsistent trends in the four cultivars.The activities of polygalacturonase(PG),β-galactosidase(β-gal),cellulase(CEL),and pectate lyase(PL)gradually increased in four cultivars.And the activities of PG,β-gal,and CEL were higher in‘Fuji’and‘Honeycrisp’fruit with the fruit development,while the activity of PL of‘Fuji’and‘Honeycrisp’was lower than that of‘ENVY’and‘Modi’.Both four cultivars of fruit cells progressively became bigger as the fruit expanded,with looser cell arrangements and larger cell gaps.According to the qRT-PCR,the relative expression levels of MdACO and Mdβ-gal were notably enhanced.Our study showed that there were large differences in the content of ISP and hemicellulose,the activity of PL and the relative expression of Mdβ-gal between two different types of apple cultivars,and these differences might be responsible for the variations in the texture of the four cultivars.

Brittle culm 25, which encodes an UDP-xylose synthase, affects cell wall properties in rice

Because plant mechanical strength influences plant growth and development,the regulatory mechanisms underlying cell-wall synthesis deserve investigation.Rice mutants are useful for such research.We have identified a novel brittle culm 25(bc25)mutant with reduced growth and partial sterility.BC25 encodes an UDP-glucuronic acid decarboxylase involved in cellulose synthesis and belongs to the UXS family.A single-nucleotide mutation in BC25 accounts for its altered cell morphology and cellwall composition.Transmission electron microscopy analysis showed that the thickness of the secondary cell wall was reduced in bc25.Monosaccharide analysis revealed significant increases in content of rhamnose and arabinose but not of other monosaccharides,indicating that BC25 was involved in xylose synthesis with some level of functional redundancy.Enzymatic assays suggested that BC25 functions with high activity to interconvert UDP-glucuronic acid(UDP-Glc A)and UDP-xylose.GUS staining showed that BC25 was ubiquitously expressed with higher expression in culm,root and sheath,in agreement with that shown by quantitative real-time(q RT)-PCR.RNA-seq further suggested that BC25 is involved in sugar metabolism.We conclude that BC25 strongly influences rice cell wall formation.

Insights into the relations between cell wall integrity and in vitro digestion properties of granular starches in pulse cotyledon cells after dry heat treatment

Natural foods,such as whole pulses,are recommended in the dietary guidelines of the US and China.The plant cell wall structure in whole pulses has important implications for the nutritional functionalities of starch.In this study,garbanzo bean cells with varying degrees of cell wall integrity were subjected to dry heat treatment(DHT)and used to elucidate the food structure-starch digestion properties of pulse food.The morphological features suggested that all cell samples do not exhibit remarkable changes after being subjected to DHT.Molecular rearrangement and the crystallite disruption of starch granules entrapped in cells occurred during DHT as assessed by the crystal structure and thermal properties.DHT decreased the inhibitory effects of enzymes of both the soluble and insoluble components,but the digestion rate and extent of slightly and highly damaged cell samples did not exhibit significant differences compared with their native counterparts.We concluded that the starch digestion of pulse cotyledon cells is primarily determined by the intactness of the cellular structure.This study reveals the role of food structure on the ability to retain the desirable nutritional properties of starch after subjection to physical modification.

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.