A NAC transcription factor represses a module associated with xyloglucan content and regulates aluminum tolerance.

The transcriptional regulation of aluminum (Al) tolerance in plants is largely unknown, although Al toxicity restricts agricultural yields in acidic soils.. Here, we identified a NAM, ATAF1/2, and cup-shaped cotyledon 2 (NAC) transcription factor that participates in Al tolerance in Arabidopsis (Arabidopsis thaliana). Al substantially induced the transcript and protein levels of ANAC070, and loss-of-function anan070 mutants showed remarkably increased Al sensitivity, implying a beneficial role of ANAC070 in plant tolerance to Al toxicity. Further investigation revealed that more Al accumulated in the roots of anac070 mutants, especially in root cell walls, accompanied by a higher hemicellulose and xyloglucan level, implying a possible interaction between ANAC070 and genes that encode proteins responsible for the modification of xyloglucan, including xyloglucan endo-transglycosylases/hydrolase (XTH) or ANAC017. Yeast one hybrid analysis revealed a potential interaction between ANAC070 and ANAC017, but not for other XTHs. Furthermore, dual-luciferase reporter assay, RT-qPCR, and GUS analysis revealed that ANAC070 could directly repress the transcript levels of ANAC017, and knockout of ANAC017 in the anac070 mutant partially restored its Al sensitivity phenotype, indicating that ANAC070 contributes to Al tolerance mechanisms other than suppression of ANAC017 expression. Further analysis revealed that the core transcription factor SENSITIVE TO PROTON RHIZOTOXICITY1 (STOP1) and its target genes, which control Al tolerance in Arabidopsis, may also be involved in ANAC070-regulated Al tolerance. In summary, we identified a transcription factor, ANAC070, that represses the ANAC017-XTH31 module to regulate Al tolerance in Arabidopsis.

Bilateral hyperkeratosis of the nipples and areolae with linear nevus and acanthosis nigricans: A rare case report.

Hyperkeratosis of the nipples and areolae (HNA) is an uncommon skin disorder with no definite aetiology. We report a case of a 16-year-old boy, who presented with bilateral pigmentation and thickening of the nipples and areolae, accompanied with linear brown protrusions on the anterior neck and a velvet like appearance with pigmentation on the axillary bilaterlly. Based on clinical and histopathological, and dermatoscopic findings, the diagnosis of bilateral HNA accompanied by linear nevus and acanthosis nigricans was made. The skin lesions were improved by treatment with topical calcipotriol gel.

A novel aldo-keto reductase gene, OsAKR1, from rice confers higher tolerance to cadmium stress in rice by an in vivo reactive aldehyde detoxification.

Elevated levels of cadmium (Cd) have the ability to impede plant development. Aldo-keto reductases (AKRs) have been demonstrated in a number of plant species to improve tolerance to a variety of abiotic stresses by scavenging cytotoxic aldehydes; however, only a few AKRs have been identified to improve Cd tolerance. The OsAKR1 gene was extracted and identified from rice here. After being exposed to Cd, the expression of OsAKR1 dramatically rose in both roots and shoots, although more pronounced in roots. According to a subcellular localization experiment, the nucleus and cytoplasm are where OsAKR1 is primarily found. Mutants lacking OsAKR1 exhibited Cd sensitive phenotype than that of the wild-type (WT) Nipponbare (Nip), and osakr1 mutants exhibited reduced capacity to scavenge methylglyoxal (MG). Furthermore, osakr1 mutants exhibited considerably greater hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels, and increased catalase (CAT) activity in comparison to Nip. The expression of three isomeric forms of CAT was found to be considerably elevated in osakr1 mutants during Cd stress, as demonstrated by quantitative real-time PCR analysis, when compared to Nip. These results imply that OsAKR1 controlled rice's ability to withstand Cd by scavenging harmful aldehydes and turning on the reactive oxygen species (ROS) scavenging mechanism.

Brassinosteroid decreases cadmium accumulation via regulating gibberellic acid accumulation and Cd fixation capacity of root cell wall in rice (Oryza sativa).

The precise mechanism behind the association between plants' reactions to cadmium (Cd) stress and brassinosteroid (BR) remains unclear. In the current investigation, Cd stress quickly increased the endogenous BR concentration in the rice roots. Exogenous BR also increased the hemicellulose level in the root cell wall, which in turn increased its capacity to bind Cd. Simultaneously, the transcription level of genes responsible for root Cd absorption was decreased, including Natural Resistance-Associated Macrophage Protein 1/5 (OsNRAMP1/5) and a major facilitator superfamily gene called OsCd1. Ultimately, the increased expression of Heavy Metal ATPase 3 (OsHMA3) and the decreased expression of OsHMA2, which was in charge of separating Cd into vacuoles and translocating Cd to the shoots, respectively, led to a decrease in the amount of Cd that accumulated in the rice shoots. In contrast, transgenic rice lines overexpressing OsGSK2 (a negative regulator in BR signaling) accumulated more Cd, while OsGSK2 RNA interference (RNAi) rice line accumulated less Cd. Furthermore, BR increased endogenous Gibberellic acid (GA) level, and applying GA could replicate its alleviative effect. Taken together, BR decreased Cd accumulation in rice by mediating the cell wall's fixation capacity to Cd, which might relied on the buildup of the GA.

Auxin acts upstream of nitric oxide to regulate cell wall xyloglucan and its aluminium-binding capacity in Arabidopsis thaliana.

MAIN CONCLUSION: Auxin acts upstream of NO through NOA and XXT5 pathways to regulate the binding capacity of the root cell wall to Al. In our previous study, we identified an unknown mechanism by which 1-naphthaleneacetic acid (NAA) decreased the fixation of aluminum (Al) in the cell wall. Here, we observed that external application of the nitric oxide (NO) donor S-nitrosoglutathion (GSNO) increased the inhibition of Al on root elongation. Further analysis indicated that GSNO could induce Al accumulation in the roots and root cell walls, which is consistent with lower xyloglucan content. In comparison to the Columbia-0 (Col-0) wild type (WT), endogenous NO-reduced mutants noa1 (NOA pathway) and nia1nia2 (NR pathway) were more resistant to Al, with lower root Al content, higher xyloglucan content, and more Al accumulation in the root cell walls. By contrast, the xxt5 mutant with reduced xyloglucan content exhibited an Al-sensitive phenotype. Interestingly, Al treatment increased the endogenous auxin and NO levels, and the auxin levels induced under Al stress further stimulated NO production. Auxin application reduced Al retention in hemicellulose and decreased the xyloglucan content, similar to the effects observed with GSNO. In yucca and aux1-7 mutants, exogenous application of NO resulted in responses similar to those of the WT, whereas exogenous auxin had little effect on the noa1 mutant under Al stress. In addition, as auxin had similar effects on the nia1nia2 mutant and the WT, exogenous auxin and NO had little effect on the xxt5 mutant under Al stress, further confirming that auxin acts upstream of NO through NOA and XXT5 pathways to regulate the binding capacity of the root cell wall to Al.

Auxin is involved in cadmium accumulation in rice through controlling nitric oxide production and the ability of cell walls to bind cadmium.

Although auxin has been linked to plants' responses to cadmium (Cd) stress, the exact mechanism is yet elusive. The objective of the current investigation was to determine the role and the mechanism of auxin in controlling rice's Cd accumulation. Rice roots with Cd stress have higher endogenous auxin levels, and exogenous auxin combined Cd treatment could reduce root cell wall's hemicellulose content when compared with Cd treatment alone, which in turn reduced its fixation of Cd, as well as decreased the expression of OsCd1 (a major facilitator superfamily gene), OsNRAMP1/5 (Natural Resistance-Associated Macrophage Protein 1/5), OsZIP5/9 (Zinc Transporter 5/9), and OsHMA2 (Heavy Metal ATPase 2) that participated in Cd uptake and root to shoot translocation. Furthermore, less Cd accumulated in the shoots as a result of auxin's impact in increasing the expression of OsCAL1 (Cadmium accumulation in Leaf 1), OsABCG36/OsPDR9 (G-type ATP-binding cassette transporter/Pleiotropic drug resistance 9), and OsHMA3, which were in charge of Cd efflux and sequestering into vacuoles, respectively. Additionally, auxin decreased endogenous nitric oxide (NO) levels and antioxidant enzyme activity, while treatment of a NO scavenger-cPTIO-reduced auxin's alleviatory effects. In conclusion, the rice's ability to tolerate Cd toxicity was likely increased by the auxin-accelerated cell wall Cd exclusion mechanism, a pathway that controlled by the buildup of NO.

Salylic acid minimize cadmium accumulation in rice through regulating the fixation capacity of the cell wall to cadmium.

Although salylic acid (SA) has been linked to how plants react to cadmium (Cd) stress, the exact mechanism is still unknown. The endogenous SA concentration in the rice (Oryza sativa L.) roots was enhanced by Cd stress in the current investigation, and exogenous SA reduced the hemicellulose content in root cell wall, which in turn inhibited its Cd binding capacity. What's more, exogenous SA also decreased the transcription level of genes such as Natural Resistance-Associated Macrophage Protein 5 (OsNRAMP5) and a major facilitator superfamily gene-OsCd1 that responsible for root Cd absorption. Finally, less Cd was accumulated in the rice as a result of the higher expression of Heavy Metal ATPase 3 (OsHMA3), Cation/Ca exchanger 2 (OsCCX2) and Pleiotropic Drug Resistance 9 (OsPDR9/OsABCG36) that were responsible for separating Cd into vacuole and getting Cd out of cells, respectively. In contrast, mutant with low SA level accumulated more Cd. Additionally, SA enhanced endogenous nitric oxide (NO) levels, and its alleviatory effects were mimicked by a NO donor, sodium nitroprusside (SNP). In conclusion, SA enhanced rice's Cd resistance through regulating the binding capacity of the cell wall to Cd, a pathway that might dependent on the NO accumulation.

Effect of birth asphyxia on neonatal blood glucose during the early postnatal life: A multi-center study in Hubei Province, China.

BACKGROUND: Birth asphyxia causes hypoxia or inadequate perfusion to the organs of newborns, leading to metabolism dysfunctions including blood glucose disorders. METHODS: Neonates with and without birth asphyxia were retrospectively recruited from 53 hospitals in Hubei Province from January 1 to December 31, 2018. In summary, 875, 1139, and 180 cases in the control group, the mild asphyxia group, and the severe asphyxia group were recruited, respectively. Neonatal blood glucose values at postnatal 1, 2, 6, and 12 h (time error within 0.5 h was allowed) were gathered from the medical records. RESULTS: The incidence rates of hyperglycemia in the control group, the mild asphyxia group and the severe asphyxia group were 2.97%, 7.90%, and 23.33%, respectively (p < 0.001). Additionally, the incidence rates of hypoglycemia in the three groups above were 3.66%, 4.13%, and 7.78%, respectively (p = 0.042). The blood glucose values of neonates with hypoglycemia in the asphyxia group were lower than in the control group (p = 0.003). Furthermore, the blood glucose values of neonates with hyperglycemia were highest in the severe asphyxia group (p < 0.001). There were 778 and 117 cases with blood glucose records at four predefined time points in the mild and severe asphyxia group, respectively. The incidence of blood glucose disorders in the mild asphyxia group significantly decreased from postnatal 6 h (p＜0.05). However, we found no obvious changes of the incidence of glucose disorders within postnatal 12 h in the severe asphyxia group (p = 0.589). CONCLUSION: Birth asphyxia is likely to cause neonatal blood glucose disorders, both hypoglycemia and hyperglycemia, during the early postnatal life. The neonates with severe asphyxia have higher incidence, worse severity and longer duration of blood glucose disorders than neonates with mild asphyxia.

Melatonin reduces cadmium accumulation via mediating the nitric oxide accumulation and increasing the cell wall fixation capacity of cadmium in rice.

Melatonin (MT) is participated in plants' response to cadmium (Cd) tolerance, although its work model remains elusive. Here, the function of MT in adjusting Cd accumulation in rice was investigated. 'Nipponbare' (Nip) was cultured in the -Cd (1/2 Kimura B), -Cd + MT (1/2 Kimura B with 1 µM MT), +Cd (1/2 Kimura B plus 1 µM Cd) and +Cd + MT (1/2 Kimura B with 1 µM Cd and 1 µM MT) nutrient solutions for 7 d. Cd markedly induced the endogenous MT accumulation in rice roots and shoots, even within 1 h. MT applied exogenously elevated the hemicelluloses level, which in turn increased the cell wall's binding capacity to Cd. Furthermore, MT applied exogenously down-regulated the transcription level of Natural Resistance-Associated Macrophage Protein 1 (OsNRAMP1), OsNRAMP5, a major facilitator superfamily gene (OsCd1), and IRON-REGULATED TRANSPORTER 1 (OsIRT1), all of which were responsible for Cd intake, thus less Cd was entered into roots. Moreover, MT applied exogenously also up-regulated transcription level of Cadmium accumulation in Leaf 1 (OsCAL1) and Heavy Metal ATPase 3 (OsHMA3), two genes both attributed to the decreased Cd accumulation in shoots through expelling Cd out of cells and chelating Cd in the vacuoles, respectively. In addition, MT applied exogenously further aggravated the production of nitric oxide (NO) that induced by Cd, while application of a NO donor-SNP mimicked this alleviatory effect of the MT, indicating MT decreased rice Cd accumulation relied on the accumulation of NO.

Beyond iron-storage pool: functions of plant apoplastic iron during stress.

Iron (Fe) is an essential micronutrient for plants, and its storage in the apoplast represents an important Fe pool. Plants have developed various strategies to reutilize this apoplastic Fe pool to adapt to Fe deficiency. In addition, growing evidence indicates that the dynamic changes in apoplastic Fe are critical for plant adaptation to other stresses, including ammonium stress, phosphate deficiency, and pathogen attack. In this review, we discuss and scrutinize the relevance of apoplastic Fe for plant behavior changes in response to stress cues. We mainly focus on the relevant components that modulate the actions and downstream events of apoplastic Fe in stress signaling networks.

The endo-beta mannase MAN7 contributes to cadmium tolerance by modulating root cell wall binding capacity in Arabidopsis thaliana.

The heavy metal cadmium (Cd) is detrimental to crop growth and threatens human health through the food chain. To cope with Cd toxicity, plants employ multiple strategies to decrease Cd uptake and its root-to-shoot translocation. However, genes that participate in the Cd-induced transcriptional regulatory network, including those encoding transcription factors, remain largely unidentified. In this study, we demonstrate that ENDO-BETA-MANNASE 7 (MAN7) is necessary for the response of Arabidopsis thaliana to toxic Cd levels. We show that MAN7 is responsible for mannase activity and modulates mannose content in the cell wall, which plays a role in Cd compartmentalization in the cell wall under Cd toxicity conditions. Additionally, the repression of root growth by Cd was partially reversed via exogenous application of mannose, suggesting that MAN7-mediated cell wall Cd redistribution depends on the mannose pathway. Notably, we identified a basic leucine zipper (bZIP) transcription factor, bZIP44, that acts upstream of MAN7 in response to Cd toxicity. Transient dual-luciferase assays indicated that bZIP44 directly binds to the MAN7 promoter region and activates its transcription. Loss of bZIP44 function was associated with greater sensitivity to Cd treatment and higher accumulation of the heavy metal in roots and shoots. Moreover, MAN7 overexpression relieved the inhibition of root elongation seen in the bzip44 mutant under Cd toxicity conditions. This study thus reveals a pathway showing that MAN7-associated Cd tolerance in Arabidopsis is controlled by bZIP44 upon Cd exposure.

The upstream regulation of the root cell wall when Arabidopsis thaliana in response to toxic metal ions focusing on Al.

In acid soil, aluminum (Al) toxicity is one of the main factors limiting agricultural output. As is known to all, the cell wall is the first line of defense against metals that serves as a significant target of Al toxicity and also is crucial for Al detoxification. However, nothing is known about how this process is transcriptionally regulated. Here, we describe recent findings to understand the role of two kinds of transcription factors in regulating the cell wall composition and modification in response to Al stress in Arabidopsis thaliana. ANAC017 encodes a NAM, ATAF1/2, and cup-shaped cotyledon 2 (NAC) transcription factor, loss function of ANAC017 enhanced Al tolerance with the decreased Al content and xyloglucan content in the cell wall. Next, we characterized one xyloglucan endotransglucosylase/hydrolase (XTH), XTH31, which is previously reported to participate in Al stress, acted downstream of ANAC017 to regulate Al tolerance in Arabidopsis. In addition, we also identified MYB103, an R2R3-type transcription factor. MYB103 disruption caused Al sensitivity, and myb103 mutants' xyloglucan had a high O-acetylation level. Additionally, it was discovered that TRICHOME BIREFRINGENCE-LIKE27 (TBL27), which is in charge of xyloglucan's O-acetylation, functions downstream of MYB103 through the direct binding of the MYB103 to the promoter of the TBL27 to influence Arabidopsis's sensitivity to Al. In summary, our research showed that two distinct molecular modules modulate Arabidopsis cell wall composition and modification to positively influence Al resistance.

Decrease in hemicellulose content and its retention of iron contributes to phosphorus deficiency alleviated iron deficiency in Arabidopsis thaliana.

The physiological and molecular mechanisms between phosphorus (P) and iron (Fe) interactions are still elusive although they have been extensively investigated. In this study, we uncovered that limiting P supply could alleviate Fe deficiency in Arabidopsis (Col-0). Under Fe deficiency, P deficiency (-Fe-P) decreased cell wall Fe accumulation in root, but elevated Fe accumulation in the shoot, implying that the reduced Fe retention in the root cell wall may contribute to the P-deficiency-alleviated Fe deficiency in the shoot. On the other hand, increasing P supply could mimic the degree of Fe deficiency in terms of the expressions of genes induced after Fe deficient treatment. The components of the root cell wall showed that there was no distinction in the pectin content and the Fe retention in pectin between -Fe and -Fe-P treatments, while hemicellulose 1 content and Fe retained in it were decreased significantly in -Fe-P treatment as compared with -Fe treatment. The time-course experiment showed that decreasing cell wall retained Fe was mainly from the corresponding decrease in hemicellulose 1 retained Fe. Furthermore, the up-regulation of IRT1 expression in -Fe-P was obviously lower than -Fe. All these suggest that the P deficiency-induced decrease of hemicellulose 1 component leads to reutilization of root cell wall Fe and improvement of Fe nutrition in shoot in Fe deficient Arabidopsis. Our results provide a novel explanation of the interplay between Fe and P in Arabidopsis.

Influence of early fluid overload on bronchopulmonary dysplasia in very low-birth-weight infants.

Objective: This study aimed to determine the influence of fluid overload on bronchopulmonary dysplasia (BPD) in very low-birth-weight infants (VLBWI) within 1 week after birth. Methods: This was a retrospective case control study conducted in the Jingzhou Central Hospital. The clinical data of VLBWI (with a birth weight [BW] < 1,500 g and 26 weeks ≤ gestational age [GA] < 32 weeks) who were admitted to the neonatal intensive care unit of this hospital from January 2016 to December 2021 were analyzed retrospectively. A total of 157 cases were enrolled and divided into a BPD group (n = 60) and a non-BPD group (n = 97) according to whether BPD was present. The general condition, fluid intake, and fluid overload of the two groups of neonates within 1 week after birth were compared. The logistic regression was used to assess the association between infant characteristics and BPD. The ROC curve was used to assess how well the 7 day cumulative fluid overload predicted BPD, and to identify an optimal cut off for prediction. Results: The comparison of the patients' general condition revealed that the neonates in the BPD group had a younger GA, lower BW, lower 5-min Apgar score, longer duration of invasive mechanical ventilation, and higher incidence of intrauterine infections and administration of surfactants (P < 0.05). The differences in the other indicators were not statistically significant between the two groups. The logistic regression analysis revealed that a younger GA, the presence of intrauterine infection, and a 7-day cumulative fluid overload were the risk factors for the development of BPD. A ROC curve was plotted with the 7-day cumulative fluid overload as the test variable and BPD as the status variable. The area under the curve was 0.75 (95% confidence interval: 0.664-0.826, P = 0.042), with a sensitivity of 76.7% and a specificity of 70.1%, corresponding to a 7-day cumulative fluid overload of 36.2%. Conclusion: A younger GA, the presence of intrauterine infection, and a 7-day cumulative fluid overload were risk factors for the development of BPD. A 7 day cumulative fluid overload threshold of 36.2% best predicted the development of BPD.

Research of the Algebraic Multigrid Method for Electron Optical Simulator.

At present, electron optical simulator (EOS) takes a long time to solve linear FEM systems. The algebraic multigrid preconditioned conjugate gradient (AMGPCG) method can improve the efficiency of solving systems. This paper is focused on the implementation of the AMGPCG method in EOS. The aggregation-based scheme, which uses two passes of a pairwise matching algorithm and the K-cyle scheme, is adopted in the aggregation-based algebraic multigrid method. Numerical experiments show the advantages and disadvantages of the AMG algorithm in peak memory and solving efficiency. The AMGPCG is more efficient than the iterative methods used in the past and only needs one coarsening when EOS computes the particle motion trajectory.

Salicylic Acid Acts Upstream of Auxin and Nitric Oxide (NO) in Cell Wall Phosphorus Remobilization in Phosphorus Deficient Rice.

Salicylic acid (SA) is thought to be involved in phosphorus (P) stress response in plants, but the underlying molecular mechanisms are poorly understood. Here, we showed that P deficiency significantly increased the endogenous SA content by inducing the SA synthesis pathway, especially for up-regulating the expression of PAL3. Furthermore, rice SA synthetic mutants pal3 exhibited the decreased root and shoot soluble P content, indicating that SA is involved in P homeostasis in plants. Subsequently, application of exogenous SA could increase the root and shoot soluble P content through regulating the root and shoot cell wall P reutilization. In addition, - P + SA treatment highly upregulated the expression of P transporters such as OsPT2 and OsPT6, together with the increased xylem P content, suggesting that SA also participates in the translocation of the P from the root to the shoot. Moreover, both signal molecular nitric oxide (NO) and auxin (IAA) production were enhanced when SA is applied while the addition of respective inhibitor c-PTIO (NO scavenger) and NPA (IAA transport inhibitor) significantly decreased the root and shoot cell wall P remobilization in response to P starvation. Taken together, here SA-IAA-NO-cell wall P reutilization pathway has been discovered in P-starved rice.

Auxin facilitates cell wall phosphorus reutilization in a nitric oxide-ethylene dependent manner in phosphorus deficient rice (Oryza sativa L.).

Auxin is involved in stress responses of plants, such as phosphorus (P) deficiency in rice. Studies on whether auxin participates in cell-wall inorganic phosphorous (Pi) reutilization in Pi-starved rice are scarce. This study explored the mechanisms underlying auxin-facilitated cell-wall Pi-reutilization in rice roots. Pi deficiency rapidly induced auxin accumulation in roots; exogenous auxin [α-naphthaleneacetic acid (NAA), a permeable analog of auxin] elevated soluble Pi content in roots and shoots by increasing pectin content by enhancing activity of pectin methylesterase, and upregulating the transcript level of PHOSPHORUS-TRANSPORTER-2, such that more Pi was translocated to the shoot. Irrespective of the Pi status, exogenous auxin induced nitric oxide (NO) and ethylene production, while exogenous sodium nitroprusside (an NO donor) and 1-aminocyclopropane-1-carboxylic acid (a precursor of ethylene) had no effect on auxin content, suggesting that auxin may act upstream of NO and ethylene. The beneficial effect of NAA in increasing soluble Pi content in roots and shoots disappeared when 2-(4-carboxyphenyl)- 4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (a scavenger of NO) or aminoethoxyvinylglycine (an inhibitor of ethylene) were applied, suggesting that auxin facilitates cell-wall Pi-reutilization in a NO-ethylene-dependent manner in Pi-deficient rice. Our study results suggest auxin application as an effective agronomic practice for improving plant Pi nutrition in P-deficient conditions.

Gibberellic acid alleviates cadmium toxicity in rice by regulating NO accumulation and cell wall fixation capacity of cadmium.

Gibberellic acid (GA) has been implicated in the response of plants to cadmium (Cd) stress, but the underlying mechanism remains unclear. In the present study, our aim was to confirm the role of GA in regulating the accumulation of Cd in rice. We found that Cd stress elevated the endogenous GA level in the rice roots. Exogenous GA application not only decreased the fixation of Cd in the root cell wall through reducing the hemicelluloses content, but also decreased the expression of OsNRAMP5 (Natural Resistance-Associated Macrophage Protein 5) and OsCd1 (a major facilitator superfamily gene). Both OsNRAMP5 and OsCd1 are related to Cd absorption, therefore, less Cd was accumulated in the roots. Furthermore, GA increased the expression of OsHMA3 (Heavy Metal ATPase 3) and OsCAL1 (Cadmium accumulation in Leaf 1), which are responsible for sequestering the Cd to the vacuoles and effluxing the Cd outside the cell, respectively, as a result, less Cd was accumulated in the shoots. In contrast, more Cd was accumulated in GA deficient lines. Furthermore, GA decreased the endogenous NO levels and the activity of antioxidant enzymes, while application of a NO scavenger-cPTIO diminished the alleviatory role of GA. In summary, the GA accelerated cell wall Cd exclusion mechanism probably improved rice tolerance to Cd toxicity via regulating the accumulation of NO.

Transcription factor ANAC004 enhances Cd tolerance in Arabidopsis thaliana by regulating cell wall fixation, translocation and vacuolar detoxification of Cd, ABA accumulation and antioxidant capacity.

Cadmium (Cd) is toxic to plants, which have evolved multiple strategies to cope with Cd stress. In this study, we identified a nucleus-localized NAC-type transcription factor, ANAC004, which is induced by Cd and involved in regulating Cd resistance in Arabidopsis. First, anac004 mutants exhibited Cd sensitive phenotype and accumulated more Cd (12-23% higher than wild type in roots and shoots); plants overexpressing ANAC004 showed the opposite phenotype and with lower Cd accumulation. Second, ANAC004 enhanced Cd fixation in cell wall hemicellulose, thus reducing Cd2+ influx into root cells. Third, ANAC004 was involved in the process of vacuolar Cd compartmentalization by regulating the genes associated with Cd detoxification (PCS1/2, NAS4, ABCC1/2/3, MTP1/3, IREG2 and NRAMP3/4). Fourth, ANAC004 reduced root-to-shoot Cd translocation through down-regulated Cd translocation-related genes (HMA2 and HMA4). Finally, the expression of genes related to ABA synthesis (AAO3, MCSU, and NCED3) and the activities of antioxidant enzymes (SOD, POD and CAT) were all reduced in anac004 mutants, leading to reduced levels of endogenous ABA and increased accumulation of reactive oxygen species (O2.- and H2O2) and MDA, which ultimately weakened resistance to Cd. Our results suggest that ANAC004 decreases Cd accumulation in Arabidopsis through enhancing cell wall Cd immobilization, increasing vacuolar Cd detoxification, and inhibiting Cd translocation, thus improving Cd resistance, processes that might be mediated by ABA signaling and antioxidant defense systems.