Search

Aluminum toxicity is a major abiotic stress on acidic soils, leading to restricted root growth and reduced plant yield. Long non-coding RNAs are crucial signaling molecules regulating the expression of downstream genes, particularly under abiotic stress conditions. However, the extent to which lncRNAs participate in the response to aluminum (Al) stress in barley remains largely unknown. Here, we conducted RNA sequencing of root samples under aluminum stress and compared the lncRNA transcriptomes of two Tibetan wild barley genotypes, XZ16 (Al-tolerant) and XZ61 (Al-sensitive), as well as the aluminum-tolerant cultivar Dayton. In total, 268 lncRNAs were identified as aluminum-responsive genes on the basis of their differential expression profiles under aluminum treatment. Through target gene prediction analysis, we identified 938 candidate lncRNA-messenger RNA (mRNA) pairs that function in a cis-acting manner. Subsequently, enrichment analysis showed that the genes targeted by aluminum-responsive lncRNAs were involved in diterpenoid biosynthesis, peroxisome function, and starch/sucrose metabolism. Further analysis of genotype differences in the transcriptome led to the identification of 15 aluminum-responsive lncRNAs specifically altered by aluminum stress in XZ16. The RNA sequencing data were further validated by RT-qPCR. The functional roles of lncRNA-mRNA interactions demonstrated that these lncRNAs are involved in the signal transduction of secondary messengers, and a disease resistance protein, such as RPP13-like protein 4, is probably involved in aluminum tolerance in XZ16. The current findings significantly contribute to our understanding of the regulatory roles of lncRNAs in aluminum tolerance and extend our knowledge of their importance in plant responses to aluminum stress. [ABSTRACT FROM AUTHOR]

Aluminum (Al) stress is a dominant obstacle for plant growth in acidic soil, which accounts for approximately 40–50% of the world's potential arable land. The identification and characterization of Al stress response (Al-SR) genes in Arabidopsis, rice, and other plants have deepened our understanding of Al's molecular mechanisms. However, as a crop sensitive to acidic soil, only eight Al-SR genes have been identified and functionally characterized in maize. In this review, we summarize the Al-SR genes in plants, including their classifications, subcellular localizations, expression organs, functions, and primarily molecular regulatory networks. Moreover, we predict 166 putative Al-SR genes in maize based on orthologue analyses, facilitating a comprehensive understanding of the impact of Al stress on maize growth and development. Finally, we highlight the potential applications of alleviating Al toxicity in crop production. This review deepens our understanding of the Al response in plants and provides a blueprint for alleviating Al toxicity in crop production. [ABSTRACT FROM AUTHOR]

Aluminum (Al) is the most abundant element in the earth crust. Due to the abuse of phosphate fertilizer, acid rain has been frequently observed in recent years, resulting in the conversion of non-toxic aluminosilicates in the soil into Al ions, thereby causing stress to plants. As a DNA methylation inhibitor, curcumin can effectively counteract the Al stress on plants, while the epigenetic mechanism remains unclear. This study discusses the epigenetic mechanism of curcumin counteracting Al stress on grape. The results demonstrated that curcumin could significantly relieve the Al stress symptoms of grapes and reduce its whole genome methylation level. Al stress and curcumin treatment did not cause variations in the methylation level in each chromosome. While Al stress led to a slight increase in the average methylation level of each chromosome, and treatment by curcumin led to a significant decrease in the average methylation level of each chromosome. Specifically, the sites of CG and CHG were decreased significantly, and the site of CHH was increased or decreased significantly. Analysis of differentially-methylated regions (DMRs) revealed that treatment by curcumin led to an increase in hypo-DMRs in the whole genome of grape, and analysis of differentially-methylated genes (DMGs) also identified differentially related genes of hypo-DMRs in the whole genome of grapes, suggesting that curcumin triggers responses to Al stress by regulating hypo-methylation mode of the whole genome of grape. Additionally, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis demonstrated that DMGs of grapes generate responses to Al stress by participating in galactose metabolism, ascorbate, and aldarate metabolism, and amino sugar and nucleotide sugar metabolism pathways of carbohydrate metabolism in the KEGG subclass. [ABSTRACT FROM AUTHOR]

Summary: Aluminium (Al) toxicity decreases crop production in acid soils in general, but many crops have evolved complex mechanisms to resist it. However, our current understanding of how plants cope with Al stress and perform Al resistance is still at the initial stage. In this study, the citrate transporter CcMATE35 was identified to be involved in Al stress response. The release of citrate was increased substantially in CcMATE35 over‐expression (OE) lines under Al stress, indicating enhanced Al resistance. It was demonstrated that transcription factor CcNFYB3 regulated the expression of CcMATE35, promoting the release of citrate from roots to increase Al resistance in pigeon pea. We also found that a Long noncoding RNA Targeting Citrate Synthase (CcLTCS) is involved in Al resistance in pigeon pea. Compared with controls, overexpression of CcLTCS elevated the expression level of the Citrate Synthase gene (CcCS), leading to increases in root citrate level and citrate release, which forms another module to regulate Al resistance in pigeon pea. Simultaneous overexpression of CcNFYB3 and CcLTCS further increased Al resistance. Taken together, these findings suggest that the two modules, CcNFYB3‐CcMATE35 and CcLTCS‐CcCS, jointly regulate the efflux and synthesis of citrate and may play an important role in enhancing the resistance of pigeon pea under Al stress. [ABSTRACT FROM AUTHOR]

Soybean is one of the most significant oilseed and vital food crops. Soybean growth and yield have been significantly affected by abiotic stresses. Heavy metal stress like Al toxicity is the most serious threat to soybean growth and yield and impairs plant growth and development. To counter the toxic effect of Al stress, breeders have used different breeding tools, including conventional breeding techniques, but the success ratio of these tools is limited because of the complex genetic mechanism of Al tolerance. Due to advancements in molecular biology, researchers have identified many potential genes and quantitative trait loci (QTL) involved in soybean response to Al stress. Some were successfully cloned and transformed to develop Al-resilient soybean genotypes. Genetic diversity has played a key role in improving the plant breeding program. Unfortunately, due to genetic erosion, the beneficial alleles have been threatened, and hence, significant efforts should be done to safeguard the plant germplasm for future use. As mentioned in this review, potential molecular techniques like transcription factors (TFs) and genetic engineering have been used to identify the molecular factors regulating Al tolerance and the development of transgenic soybean cultivars. The clustered regularly interspaced short palindromic repeats (CRISPR/Cas9) technique has been developed, which can alter the desired gene to bring targeted results in soybean, but it has not been broadly used to amend the Al-tolerant genes in soybean. Despite all these efforts, the Al tolerance mechanism has not been fully explored. Hence, more efforts are needed to adopt a more useful way to breed the Al-tolerant cultivars by targeting the identified genes/QTL, as mentioned in this review. This review will be a significant piece of information for future researchers to understand the genetic mechanism of Al tolerance in soybean. [ABSTRACT FROM AUTHOR]

Aluminum toxicity is a major abiotic stress on acidic soils, leading to restricted root growth and reduced plant yield. Long non-coding RNAs are crucial signaling molecules regulating the expression of downstream genes, particularly under abiotic stress conditions. However, the extent to which lncRNAs participate in the response to aluminum (Al) stress in barley remains largely unknown. Here, we conducted RNA sequencing of root samples under aluminum stress and compared the lncRNA transcriptomes of two Tibetan wild barley genotypes, XZ16 (Al-tolerant) and XZ61 (Al-sensitive), as well as the aluminum-tolerant cultivar Dayton. In total, 268 lncRNAs were identified as aluminum-responsive genes on the basis of their differential expression profiles under aluminum treatment. Through target gene prediction analysis, we identified 938 candidate lncRNA-messenger RNA (mRNA) pairs that function in a cis-acting manner. Subsequently, enrichment analysis showed that the genes targeted by aluminum-responsive lncRNAs were involved in diterpenoid biosynthesis, peroxisome function, and starch/sucrose metabolism. Further analysis of genotype differences in the transcriptome led to the identification of 15 aluminum-responsive lncRNAs specifically altered by aluminum stress in XZ16. The RNA sequencing data were further validated by RT-qPCR. The functional roles of lncRNA-mRNA interactions demonstrated that these lncRNAs are involved in the signal transduction of secondary messengers, and a disease resistance protein, such as RPP13-like protein 4, is probably involved in aluminum tolerance in XZ16. The current findings significantly contribute to our understanding of the regulatory roles of lncRNAs in aluminum tolerance and extend our knowledge of their importance in plant responses to aluminum stress.

Aluminum (Al) stress is a dominant obstacle for plant growth in acidic soil, which accounts for approximately 40–50% of the world’s potential arable land. The identification and characterization of Al stress response (Al-SR) genes in Arabidopsis, rice, and other plants have deepened our understanding of Al’s molecular mechanisms. However, as a crop sensitive to acidic soil, only eight Al-SR genes have been identified and functionally characterized in maize. In this review, we summarize the Al-SR genes in plants, including their classifications, subcellular localizations, expression organs, functions, and primarily molecular regulatory networks. Moreover, we predict 166 putative Al-SR genes in maize based on orthologue analyses, facilitating a comprehensive understanding of the impact of Al stress on maize growth and development. Finally, we highlight the potential applications of alleviating Al toxicity in crop production. This review deepens our understanding of the Al response in plants and provides a blueprint for alleviating Al toxicity in crop production.

The ethylene response factor (ERF) transcription factors, which is one of the largest transcription factor families in plants, are involved in biological and abiotic stress response and play an important role in plant growth and development. In this study, the GmABR1 gene from the soybean inbred line Zhonghuang24 (ZH24)×Huaxia 3 (HX3) was investigated its aluminum (Al) tolerance. GmABR1 protein has a conserved domain AP2, which is located in the nucleus and has transcriptional activation ability. The results of real-time quantitative PCR (qRTPCR) showed that the GmABR1 gene presented a constitutive expression pattern rich in the root tip, stem and leaf tissues of HX3. After Al stress, the GmABR1 transcript was significantly increased in the roots. The transcripts of GmABR1 in the roots of HX3 treated with 50 µM AlCl3 was 51 times than that of the control. The GmABR1 was spatiotemporally specific with the highest expression levels when Al concentration was 50 µM, which was about 36 times than that of the control. The results of hematoxylin staining showed that the root tips of GmABR1-overexpression lines were stained the lightest, followed by the control, and the root tips of GmABR1 RNAi lines were stained the darkest. The concentrations of Al3+ in root tips were 207.40 µg/g, 147.74 µg/g and 330.65 µg/ g in wild type (WT), overexpressed lines and RNAi lines, respectively. When AlCl3 (pH4.5) concentration was 100 µM, all the roots of Arabidopsis were significantly inhibited. The taproot elongation of WT, GmABR1 transgenic lines was 69.6%, 85.6%, respectively. When treated with Al, the content of malondialdehyde (MDA) in leaves of WT increased to 3.03 µg/g, while that of transgenic Arabidopsis increased from 1.66-2.21 µg/g, which was lower than that of WT. Under the Al stress, the Al stress responsive genes such as AtALMT1 and AtMATE, and the genes related to ABA pathway such as AtABI1, AtRD22 and AtRD29A were upregulated. The results indicated that GmABR1 may jointly regulate plant resistance to Al stress through genes related to Al stress response and ABA response pathways. [ABSTRACT FROM AUTHOR]

Over 40% of arable land in the world is acidic. Al stress has become a global agricultural problem affecting plant growth and limiting crop production in acidic soils. Plants have evolved different regulatory mechanisms of adaptation to exogenous environmental challenges, such as Al stress, by altering their growth patterns. In the past decades, several key genes involved in plant response to Al stress and the mechanism of Al detoxification have been revealed. However, the signaling pathways of plant response to Al stress and the regulatory mechanism of plant Al tolerance remain poorly understood. In this review, we summarized the findings of recent studies on the plant Al tolerance mechanism and the molecular regulation mechanism of phytohormones in response to Al stress. This review improves our understanding of the regulatory mechanisms of plants in response to Al stress and provides a reference for the breeding of Al-tolerant crops.

The WRKY transcription factors (TFs) are one of the largest families of TFs in plants and play multiple roles in plant growth and development and stress response. In this study, GmWRKY21 encoding a WRKY transcription factor was functionally characterized in Arabidopsis and soybean. The GmWRKY21 protein containing a highly conserved WRKY domain and a C2H2 zinc-finger structure is located in the nucleus and has the characteristics of transcriptional activation ability. The GmWRKY21 gene presented a constitutive expression pattern rich in the roots, leaves, and flowers of soybean with over 6-fold of relative expression levels and could be substantially induced by aluminum stress. As compared to the control, overexpression of GmWRKY21 in Arabidopsis increased the root growth of seedlings in transgenic lines under the AlCl3 concentrations of 25, 50, and 100µM with higher proline and lower MDA accumulation. The results of quantitative real-time polymerase chain reaction (qRT-PCR) showed that the marker genes relative to aluminum stress including ALMT, ALS3, MATE, and STOP1 were induced in GmWRKY21 transgenic plants under AlCl3 treatment. The stress-related genes, such as KIN1, COR15A, COR15B, COR47, GLOS3, and RD29A, were also upregulated in GmWRKY21 transgenic Arabidopsis under aluminum stress. Similarly, stress-related genes, such as GmCOR47, GmDREB2A, GmMYB84, GmKIN1, GmGST1, and GmLEA, were upregulated in hair roots of GmWRKY21 transgenic plants. In summary, these results suggested that the GmWRKY21 transcription factor may promote the tolerance to aluminum stress mediated by the pathways regulating the expression of the acidic aluminum stress-responsive genes and abiotic stress-responsive genes. [ABSTRACT FROM AUTHOR]

• The full length of Rhododendron micranthum Turcz. RmCS was isolated and identified. • RmCS was preferentially expressed in stem, autumn leaf and initial flowering stage. • Overexpression of RmCS increased salt tolerance, alkali tolerance, drought tolerance and aluminum tolerance of transgenic tobacco, but decreased plant height and leaf area. • The roots of tobacco plants overexpressing RmCS secreted higher concentrations of malic acid, citric acid and tartaric acid. Citrate synthase (CS) is a rate-limiting enzyme in tricarboxylic acid (TCA) cycle, which is related to numerous plant physiological events, like mitochondrial energy metabolism and stress resistance, and has a key function in aluminum (Al) stress response. Rhododendron micranthum Turcz. has been used as ornamental plants worldwide. This species prefers acidic soils, and thus its growth and ornamental quality are often limited by Al toxicity. In the present work, the full-length cDNA encoding a CS (here designated RmCS) was isolated and characterized. The RmCS contained the conserved CS domain and a N-terminal PWPN-box. RmCS protein was predicted to be localized to the cytoplasm and mitochondria. A neighbor-joining tree indicated that RmCS was similar to CS proteins of Actinidia chinensis var. chinensis and Vitis riparia the most. RmCS was highly expressed in stems; particularly, it shows predominant expression in flowers in the first flowering period, whereas in leaves peak expression levels were detected in September. Southern blotting analysis demonstrated that one to three copies of RmCS were successfully integrated in the genome of transgenic tobacco. Overexpression of RmCS significantly increased salt, alkali, drought, and Al tolerance, but reduced the plant height and leaf area, of transgenic tobacco. Roots of RmCS -overexpressing tobacco plants secreted higher concentrations of malic acid, citric acid, and tartaric acid. Decreased malonaldehyde while elevated proline contents in the leaf suggested that the improved abiotic stress tolerance conferred by RmCS was associated with decreased membrane damage and improved osmotic adjustment. The above findings indicated the potentially vital function of RmCS in abiotic stress responses of R. micranthum , and lays certain theoretical foundation for improving stress resistance of R. micranthum. [ABSTRACT FROM AUTHOR]

Abstract Background As an important cash crop, the yield of peanut is influenced by soil acidification and pathogen infection. Receptor-like protein kinases play important roles in plant growth, development and stress responses. However, little is known about the number, location, structure, molecular phylogeny, and expression of RLKs in peanut, and no comprehensive analysis of RLKs in the Al stress response in peanuts have been reported. Results A total of 1311 AhRLKs were identified from the peanut genome. The AhLRR-RLKs and AhLecRLKs were further divided into 24 and 35 subfamilies, respectively. The AhRLKs were randomly distributed across all 20 chromosomes in the peanut. Among these AhRLKs, 9.53% and 61.78% originated from tandem duplications and segmental duplications, respectively. The ka/ks ratios of 96.97% (96/99) of tandem duplication gene pairs and 98.78% (646/654) of segmental duplication gene pairs were less than 1. Among the tested tandem duplication clusters, there were 28 gene conversion events. Moreover, all total of 90 Al-responsive AhRLKs were identified by mining transcriptome data, and they were divided into 7 groups. Most of the Al-responsive AhRLKs that clustered together had similar motifs and evolutionarily conserved structures. The gene expression patterns of these genes in different tissues were further analysed, and tissue-specifically expressed genes, including 14 root-specific Al-responsive AhRLKs were found. In addition, all 90 Al-responsive AhRLKs which were distributed unevenly in the subfamilies of AhRLKs, showed different expression patterns between the two peanut varieties (Al-sensitive and Al-tolerant) under Al stress. Conclusions In this study, we analysed the RLK gene family in the peanut genome. Segmental duplication events were the main driving force for AhRLK evolution, and most AhRLKs subject to purifying selection. A total of 90 genes were identified as Al-responsive AhRLKs, and the classification, conserved motifs, structures, tissue expression patterns and predicted functions of Al-responsive AhRLKs were further analysed and discussed, revealing their putative roles. This study provides a better understanding of the structures and functions of AhRLKs and Al-responsive AhRLKs.

The toxicity of aluminum (Al) in acidic soil inhibits plant development and reduces crop yields. Programmed cell death (PCD) is one of the important mechanisms in the plant response to Al toxicity. However, it is yet unknown if S -nitrosoglutathione reductase (GSNOR) provides Al-PCD. Here, transcription and protein expression of AhGSNOR1 were both induced by Al stress. AhGSNOR1- overexpressing transgenic tobacco plants reduced Al-induced nitric oxide (NO) and S -nitrosothiol accumulation, the inhibitory effect of Al stress on root elongation and the degree of cell death, and enhanced antioxidant enzyme activity to effectively remove hydrogen peroxide. In addition, AhGSNOR1 directly interacted with AhTRXh in vivo. Expression of Trxh3 in AhGSNOR1- overexpressing transgenic plants was significantly upregulated, indicating that AhGSNOR1 positively regulated the transcriptional level of Trxh3. Together, these results suggested that AhGSNOR1 was a negative regulatory factor of Al-induced PCD and improved plant Al-tolerance by modulating intracellular NO and redox homeostasis. • AhGSNOR1 negatively regulated Al-induced PCD by enhancing SOD, POD and CAT activities. • AhGSNOR1 reducing the extent of lipid peroxidation and NO, SNO and H 2 O 2 levels, and maintaining intracellular NO and redox levels. • AhGSNOR1 directly interacted with AhTRXh in vivo , and AhGSNOR1 positively regulated the transcriptional level of Trxh3. [ABSTRACT FROM AUTHOR]

• Aluminum (Al) affected the contents of N-containing compounds in Citrus. • Al affected the activities of N metabolism–related enzymes in Citrus. • Al differentially affected N metabolism between Citrus sinensis and C. grandis. • Increased leaf GOGAT might be an index of Al–tolerance in Citrus plants. Citrus are mostly planted in tropical/subtropical acidic soil areas, and are susceptible to aluminum (Al) toxicity, which affects tree growth and fruit quality. However, the effects of Al stress on the nitrogen (N) metabolism in different Al-tolerant Citrus varieties, and whether N metabolism is related to Al-tolerance in different Citrus varieties, were remained unveiled. In the current study, Al-tolerant "Xuegan" (Citrus sinensis) and Al-sensitive "Sour pummelo" (C. grandis), were irrigated with different nutrient solutions with or without Al. Al decreased the dry weights (DW) of leaves, stems and roots, as well as the N content, the N accumulation, total soluble proteins (TSPs) and total free amino acids (TFAAs) of different tissues of C. grandis , but it increased the ratio of root DW to shoot DW. In contrast, Al did not change the parameters mentioned above, except for decreasing the content and accumulation of N in C. sinensis roots. Al did not change the content of NO 3 – in different position leaves and roots, but decreased the content of NH 4 + in C. grandis. Al decreased the content of NO 3 – in different position leaves and roots, but except for the lower leaf, Al did not change that of NH 4 + in C. sinensis. Although Al affected the activities and gene expression levels of N metabolism–related enzymes in the leaves and roots of these two Citrus species, the effects of Al on these parameters were more pronounced in C. grandis than in C. sinensis. Results from correlation analysis (CoA) and principal components analysis (PCA) indicated that the increased root DW/shoot DW and NO 3 --N content in the roots and middle/upper leaves might be the related indicators of Al toxicity, whereas the enhanced activity of leaf GOGAT might be related to the Al–tolerance in Citrus plants. In conclusion, this study preliminarily revealed that the impact of Al on N metabolism and the response of N metabolism–related indicators to Al stress in Citrus , providing scientific reference for high-yield and high-quality cultivation of Citrus grown in acidic soil areas. [Display omitted] [ABSTRACT FROM AUTHOR]

In response to changing environments, plants regulate gene expression and subsequent metabolism to acclimate and survive. A superfamily of acyl-activating enzymes (AAEs) has been observed in every class of creatures on planet. Some of plant AAE genes have been identified and functionally characterized to be involved in growth, development, biotic, and abiotic stresses via mediating diverse metabolic pathways. However, less information is available about AAEs superfamily in tomato (Solanum lycopersicum), the highest value fruit and vegetable crop globally. In this study, we aimed to identify tomato AAEs superfamily and investigate potential functions with respect to aluminum (Al) stress that represents one of the major factors limiting crop productivity on acid soils worldwide. Fifty-three AAE genes of tomato were identified and named on the basis of phylogenetic relationships between Arabidopsis and tomato. The phylogenetic analysis showed that AAEs could be classified into six clades; however, clade III contains no AAE genes of tomato. Synteny analyses revealed tomato vegetable paralogs and Arabidopsis orthologs. The RNA-seq and quantitative reverse-transcriptase PCR (qRT-PCR) analysis indicated that 9 out of 53 AAEs genes were significantly up- or downregulated by Al stress. Numerous cis -acting elements implicated in biotic and abiotic stresses were detected in the promoter regions of SlAAEs. As the most abundantly expressed gene in root apex and highly induced by Al, there are many potential STOP1 cis -acting elements present in the promoter of SlAAE3-1 , and its expression in root apex was specific to Al. Finally, transgenic tobacco lines overexpressing SlAAE3-1 displayed increased tolerance to Al. Altogether, our results pave the way for further studies on the functional characterization of SlAAE genes in tomato with a wish of improvement in tomato crop in the future. [ABSTRACT FROM AUTHOR]

Abstract Background The family of NAC proteins (NAM, ATAF1/2, and CUC2) represent a class of large plant-specific transcription factors. However, identification and functional surveys of NAC genes of tomato (Solanum lycopersicum) remain unstudied, despite the tomato genome being decoded for several years. This study aims to identify the NAC gene family and investigate their potential roles in responding to Al stress. Results Ninety-three NAC genes were identified and named in accordance with their chromosome location. Phylogenetic analysis found SlNACs are broadly distributed in 5 groups. Gene expression analysis showed that SlNACs had different expression levels in various tissues and at different fruit development stages. Cycloheximide treatment and qRT-PCR analysis indicated that SlNACs may aid regulation of tomato in response to Al stress, 19 of which were significantly up- or down-regulated in roots of tomato following Al stress. Conclusion This work establishes a knowledge base for further studies on biological functions of SlNACs in tomato and will aid in improving agricultural traits of tomato in the future.

In response to changing environments, plants regulate gene expression and subsequent metabolism to acclimate and survive. A superfamily of acyl-activating enzymes (AAEs) has been observed in every class of creatures on planet. Some of plant AAE genes have been identified and functionally characterized to be involved in growth, development, biotic, and abiotic stresses via mediating diverse metabolic pathways. However, less information is available about AAEs superfamily in tomato (Solanum lycopersicum), the highest value fruit and vegetable crop globally. In this study, we aimed to identify tomato AAEs superfamily and investigate potential functions with respect to aluminum (Al) stress that represents one of the major factors limiting crop productivity on acid soils worldwide. Fifty-three AAE genes of tomato were identified and named on the basis of phylogenetic relationships between Arabidopsis and tomato. The phylogenetic analysis showed that AAEs could be classified into six clades; however, clade III contains no AAE genes of tomato. Synteny analyses revealed tomato vegetable paralogs and Arabidopsis orthologs. The RNA-seq and quantitative reverse-transcriptase PCR (qRT-PCR) analysis indicated that 9 out of 53 AAEs genes were significantly up- or downregulated by Al stress. Numerous cis-acting elements implicated in biotic and abiotic stresses were detected in the promoter regions of SlAAEs. As the most abundantly expressed gene in root apex and highly induced by Al, there are many potential STOP1 cis-acting elements present in the promoter of SlAAE3-1, and its expression in root apex was specific to Al. Finally, transgenic tobacco lines overexpressing SlAAE3-1 displayed increased tolerance to Al. Altogether, our results pave the way for further studies on the functional characterization of SlAAE genes in tomato with a wish of improvement in tomato crop in the future.

Background: As an important cash crop, the yield of peanut is influenced by soil acidification and pathogen infection. Receptor-like protein kinases play important roles in plant growth, development and stress responses. However, little is known about the number, location, structure, molecular phylogeny, and expression of RLKs in peanut, and no comprehensive analysis of RLKs in the Al stress response in peanuts have been reported. Results: A total of 1311 AhRLKs were identified from the peanut genome. The AhLRR-RLKs and AhLecRLKs were further divided into 24 and 35 subfamilies, respectively. The AhRLKs were randomly distributed across all 20 chromosomes in the peanut. Among these AhRLKs, 9.53% and 61.78% originated from tandem duplications and segmental duplications, respectively. The ka/ks ratios of 96.97% (96/99) of tandem duplication gene pairs and 98.78% (646/654) of segmental duplication gene pairs were less than 1. Among the tested tandem duplication clusters, there were 28 gene conversion events. Moreover, all total of 90 Al-responsive AhRLKs were identified by mining transcriptome data, and they were divided into 7 groups. Most of the Al-responsive AhRLKs that clustered together had similar motifs and evolutionarily conserved structures. The gene expression patterns of these genes in different tissues were further analysed, and tissue-specifically expressed genes, including 14 root-specific Al-responsive AhRLKs were found. In addition, all 90 Al-responsive AhRLKs which were distributed unevenly in the subfamilies of AhRLKs, showed different expression patterns between the two peanut varieties (Al-sensitive and Al-tolerant) under Al stress. Conclusions: In this study, we analysed the RLK gene family in the peanut genome. Segmental duplication events were the main driving force for AhRLK evolution, and most AhRLKs subject to purifying selection. A total of 90 genes were identified as Al-responsive AhRLKs, and the classification, conserved motifs, structures, tissue expression patterns and predicted functions of Al-responsive AhRLKs were further analysed and discussed, revealing their putative roles. This study provides a better understanding of the structures and functions of AhRLKs and Al-responsive AhRLKs. [ABSTRACT FROM AUTHOR]

Background: Sugarcane is a crop of global importance and has been expanding to areas with soils containing high levels of exchangeable aluminum (Al), which is a limiting factor for crop development in acidic soils. The study of the sugarcane physiological and nutritional behavior together with patterns of gene expression in response to Al stress may provide a basis for effective strategies to increase crop productivity in acidic soils. Methods: Sugarcane cultivars were evaluated for physiological parameters (photosynthesis, stomatal conductance, and transpiration), nutrient (N, P, K, Ca, Mg, and S) and Al contents in leaves and roots and gene expression, of the genes MDH, SDH by qPCR, both related to the production of organic acids, and SOD, related to oxidative stress. Results: Brazilian sugarcane RB867515, RB928064, and RB935744 cultivars exhibited very different responses to induced stress by Al. Exposure to Al caused up-regulation (SOD and MDH) or down-regulation (SDH, MDH, and SOD), depending on the cultivar, Al level, and plant tissue. The RB867515 cultivar was the most Al-tolerant, showing no decline of nutrient content in plant tissue, photosynthesis, transpiration, and stomatal conductance after exposure to Al; it exhibited the highest Al content in the roots, and showed important MDH and SOD gene expression in the roots. RB928064 only showed low expression of SOD in roots and leaves, while RB935744 showed important expression of the SOD gene only in the leaves. Sugarcane cultivars were classified in the following descending Al-tolerance order: RB867515 > RB928064 = RB935744. These results may contribute to the obtention of Al-tolerant cultivars that can play their genetic potential in soils of low fertility and with low demand for agricultural inputs; the selection of potential plants for breeding programs; the elucidation of Al detoxification mechanisms employed by sugarcane cultivars. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effects of Al stress on the growth and nitrogen (N) absorption of maize varieties with different Al tolerance as related with chemical Al forms on maize root surfaces. Materials and methods: Three maize cultivars, Al-tolerant cultivar Taiyu 1, medium-Al-tolerant cultivar Zhengdan 958, and Al-sensitive cultivar Denghai 11, were selected for short-term and long-term Al stress with solution culture experiments. After germination, the healthy and consistent seedlings were selected for root elongation measurement. The maize seedlings were put in the Hoagland nutrient solution for 7 and 21 days to measure N absorption efficiency by maize varieties and Al chemical forms on maize roots. Results and discussion: Al stress inhibited the growth of maize, and the degree of the inhibition was positively correlated with the amount of Al accumulation on maize roots significantly (P < 0.05). The amount of Al accumulated on roots of Denghai 11 was the highest, followed by Zhengdan 958, while that of Taiyu 1 was the lowest, which was consistent with their tolerance to Al toxicity. In addition, only N absorption efficiency of the maize cultivars was inhibited, and their N accumulation was not affected by Al stress in the early stage of long-term Al stress. However, both N absorption efficiency and N accumulation of the maize cultivars were inhibited in the late stage of long-term Al stress, and the inhibition degree increased with the increase of Al concentration. Al stress showed the greatest inhibition on Al-sensitive cultivar of Denghai11. After Al stress, the Al adsorbed on maize roots was differentiated into exchangeable, complexed, precipitated, and residual Al. In the early stage of long-term Al stress, the content of complexed Al was the highest, followed by residual Al and exchangeable Al, and the precipitated Al was the lowest, while at the late stage of Al stress, the content of residual Al was the highest, followed by complexed Al. Correlation analysis showed that the chemical forms of Al on maize roots affected N absorption efficiency. Among them, the exchangeable Al and residual Al were the main Al forms that affected the nitrate-N absorption efficiency of maize roots. They showed greater influence on the Al-sensitive cultivar of maize than the Al-tolerant cultivar. Conclusions: Reducing adsorption and accumulation of Al on maize roots could decrease the inhibition of Al stress on N absorption efficiency and accumulation by maize, especially for Al-sensitive cultivar. [ABSTRACT FROM AUTHOR]

Background: The family of NAC proteins (NAM, ATAF1/2, and CUC2) represent a class of large plant-specific transcription factors. However, identification and functional surveys of NAC genes of tomato (Solanum lycopersicum) remain unstudied, despite the tomato genome being decoded for several years. This study aims to identify the NAC gene family and investigate their potential roles in responding to Al stress. Results: Ninety-three NAC genes were identified and named in accordance with their chromosome location. Phylogenetic analysis found SlNACs are broadly distributed in 5 groups. Gene expression analysis showed that SlNACs had different expression levels in various tissues and at different fruit development stages. Cycloheximide treatment and qRT-PCR analysis indicated that SlNACs may aid regulation of tomato in response to Al stress, 19 of which were significantly up- or down-regulated in roots of tomato following Al stress. Conclusion: This work establishes a knowledge base for further studies on biological functions of SlNACs in tomato and will aid in improving agricultural traits of tomato in the future. [ABSTRACT FROM AUTHOR]

Global soil acidification is increasing, enlarging aluminum (Al) availability in soils, leading to reductions in plant growth. This study investigates the effect of Al stress on the leaf growth zones of Rye (Secale cereale, cv Beira). Kinematic analysis showed that the effect of Al on leaf growth rates was mainly due to a reduced cell production rate in the meristem. Transcriptomic analysis identified 2272 significantly (log2fold > |0.5| FDR < 0.05) differentially expressed genes (DEGs) for Al stress. There was a downregulation in several DEGs associated with photosynthetic processes and an upregulation in genes for heat/light response, and H 2 O 2 production in all leaf zones. DEGs associated with heavy metals and malate transport were increased, particularly, in the meristem. To determine the putative function of these processes in Al tolerance, we performed biochemical analyses comparing the tolerant Beira with an Al sensitive variant RioDeva. Beira showed improved sugar metabolism and redox homeostasis, specifically in the meristem compared to RioDeva. Similarly, a significant increase in malate and citrate production, which are known to aid in Al detoxification in plants, was found in Beira. This suggests that Al tolerance in Rye is linked to its ability for Al exclusion from the leaf meristem. [Display omitted] ● We study the effect of Al stress on three leaf growth zones of tolerant Rye leaves. ● Kinematic and Transcriptomic, and biochemical validation were performed. ● Cell Production rate found to be leading cause for lower leaf elongation rate. ● Improved Sugar metabolism in meristem tissue improves tolerance. ● Exclusion of Al by malate and citrate likely main factor in overall leaf tolerance. [ABSTRACT FROM AUTHOR]

Aluminum (Al) usually disturbs redox homeostasis and causes irreversible oxidative damage to biomolecules in plants, efficiently removing damaged and toxic macromolecules is essential to Al tolerance. Here, we investigated the role of autophagy, a conserved cellular degradation pathway, in plant Al tolerance using two wheat genotypes with different Al sensitivity. Compared to the sensitive genotype, Al significantly upregulated the expression of autophagy-related genes (ATGs) and enhanced the formation of autophagosomes. Reinforcing autophagy by rapamycin substantially alleviated the inhibition of root growth by Al stress, accompanied by low levels of reactive oxygen species (ROS) accumulation and oxidative damage in wheat roots; whereas inhibition of autophagy by 3-methyladenine (3-MA) aggravated the adverse impacts of Al toxicity. Further experiments showed that Al significantly triggered the accumulation of oxidized proteins, particularly in the sensitive genotype. The content of Al-induced oxidized proteins was reduced by rapamycin but further increased by 3-MA in wheat roots. Wheat plants treated with the inhibitor of vacuole H+-ATPase, concanamycin A, were more sensitive to Al stress and accumulated higher levels of oxidatively-damaged proteins compared to Al treatment. These results reveal that autophagy-mediated redox homeostasis and the clearance of oxidatively damaged proteins play a crucial role in plant's tolerance to Al stress. [Display omitted] • Al tolerance is associated with upregulation of ATGs and autophagosome initiation. • Autophagy maintains redox homeostasis by eliminating Al-induced excessive ROS. • Autophagy contributes to the degradation of Al-induced oxidized proteins. [ABSTRACT FROM AUTHOR]

To elucidate the mechanism of soybean resistance to Al, physiological and biochemical indices and antioxidant enzyme expression and activities were systematically analyzed in Al-sensitive (Glycine max Merr., Yunnan Province of China, SB) and Al-resistant Dambo (Glycine max Merr., Kyoto of Japan, RB) black soybean plants. According to the results, the contents of hydrogen peroxide (H 2 O 2) and malondialdehyde (MDA) in RB root tips were significantly lower than those in SB root tips, though the opposite results occurred for soluble protein contents. Moreover, the expression and activities of superoxide dismutase (SOD, EC 1.15.1.1.1.1.1.1), peroxidase (POD, EC 1.11.1.7) and catalase (CAT, EC 1.11.1.6) under 0–400 μM Al for 0–96 h were greater in RB than in SB. However, below 100 μM Al, the activities of those enzymes in SB increased with increasing Al concentration and treatment duration, with SOD activity being lowest and CAT activity exceeding that of POD with increasing Al concentration. Overall, enzyme activity in SB treated with Al at concentrations greater than 200 μM was lower than that in the SB control (CK; not treated with Al) and decreased with treatment duration. Additionally, at Al concentrations lower than 200 μM, enzyme activities in RB were significantly greater than those in RB CK and increased with both Al concentration and treatment duration. Moreover, enzyme activity in RB treated with 400 μM Al was slightly greater than that in RB CK. Thus, CAT activity determines soybean resistance to Al. These results indicate that soybean resistance to Al can be enhanced by regulating the expression and activity of antioxidant enzymes to remove H 2 O 2 under Al stress. • Contents of H 2 O 2 , MDA and soluble protein are regulated by Al stress and treatment duration. • Expression and activity of SOD, POD and CAT are altered by Al stress and treatment duration. • CAT activity determines soybean tolerance to Al. [ABSTRACT FROM AUTHOR]

The MADS-box transcription factors (TFs) are essential in regulating plant growth and development, and conferring abiotic and metal stress resistance. This study aims to investigate GsMAS1 function in conferring tolerance to aluminum stress in Arabidopsis. The GsMAS1 from the wild soybean BW69 line encodes a MADS-box transcription factor in Glycine soja by bioinformatics analysis. The putative GsMAS1 protein was localized in the nucleus. The GsMAS1 gene was rich in soybean roots presenting a constitutive expression pattern and induced by aluminum stress with a concentration-time specific pattern. The analysis of phenotypic observation demonstrated that overexpression of GsMAS1 enhanced the tolerance of Arabidopsis plants to aluminum (Al) stress with larger values of relative root length and higher proline accumulation compared to those of wild type at the AlCl3 treatments. The genes and/or pathways regulated by GsMAS1 were further investigated under Al stress by qRT-PCR. The results indicated that six genes resistant to Al stress were upregulated, whereas AtALMT1 and STOP2 were significantly activated by Al stress and GsMAS1 overexpression. After treatment of 50 μM AlCl3, the RNA abundance of AtALMT1 and STOP2 went up to 17-fold and 37-fold than those in wild type, respectively. Whereas the RNA transcripts of AtALMT1 and STOP2 were much higher than those in wild type with over 82% and 67% of relative expression in GsMAS1 transgenic plants, respectively. In short, the results suggest that GsMAS1 may increase resistance to Al toxicity through certain pathways related to Al stress in Arabidopsis.

It has been reported that nitric oxide (NO) is a negative regulator of aluminum (Al)-induced programmed cell death (PCD) in peanut root tips. However, the inhibiting mechanism of NO on Al-induced PCD is unclear. In order to investigate the mechanism by which NO inhibits Al-induced PCD, the effects of co-treatment Al with the exogenous NO donor or the NO-specific scavenger on peanut root tips, the physiological properties of antioxidants systems and cell wall (CW) in root tip cells of NO inhibiting Al-induced PCD were studied with two peanut cultivars. The results showed that Al exposure induced endogenous NO accumulation, and endogenous NO burst increased antioxidant enzyme activity in response to Al stress. The addition of NO donor sodium nitroprusside (SNP) relieved Al-induced root elongation inhibition, cell death and Al adsorption in CW, as well as oxidative damage and ROS accumulation. Furthermore, co-treatment with the exogenous NO donor decreased MDA content, LOX activity and pectin methylesterase (PME) activity, increased xyloglucan endotransglucosylase (XET) activity and relative expression of the xyloglucan endotransglucosylase/hydrolase (XTH-32) gene. Taken together, exogenous NO alleviated Al-induced PCD by inhibiting Al adsorption in CW, enhancing antioxidant defense and reducing peroxidation of membrane lipids, alleviating the inhibition of Al on root elongation by maintaining the extensibility of CW, decreasing PME activity, and increasing XET activity and relative XTH-32 expression of CW.

The root transition zone (TZ), located between the apical meristem and basal elongation region, has a unique role in root growth and development. The root TZ is not only the active site for hormone crosstalk, but also the perception site for various environmental cues, such as aluminum (Al) stress and low phosphate (Pi) stress. We propose that the root TZ is a hot spot for the integration of diverse inputs from endogenous (hormonal) and exogenous (sensorial) stimuli to control root growth. [ABSTRACT FROM AUTHOR]

In response to aluminum (Al) stress, various plants increase their antioxidant defense system. In wheat, Al tolerance is a complex phenomenon, and whether this Al-induced response eventually enhances the ability of wheat to tolerate Al or not is still unclear and evidence is also scarce about the signals triggering it. After Al exposure, an increase in the intracellular concentration of H 2 O 2 occurred within 2 h in tolerant genotype, but was not observed in sensitive genotype. Stimulating rapid H 2 O 2 accumulation in the root tips of Yang-5 with H 2 O 2 donor relieved Al-induced root inhibition. In addition, pretreatment with H 2 O 2 donor enhanced the activity of nitrate reductase (NR), which, in turn, induced accumulation of endogenous NO in both genotypes; whereas H 2 O 2 scavenger or inhibitor blocked NO burst in roots of tolerant genotype. Conversely, Al-induced transient H 2 O 2 generation was not sensitive to NO scavenger. Scavenging or inhibition of NO burst aggravated H 2 O 2 -relieved Al-induced root inhibition as well as oxidative damage. Elevated antioxidant enzyme activities induced by H 2 O 2 donor were also suppressed by NO scavenger or NR inhibitor. These results suggest a novel signaling pathway where Al-induced transient H 2 O 2 production mediates NO burst in regulating Al-induced antioxidant defense that enhances Al resistance in wheat seedlings. [ABSTRACT FROM AUTHOR]

Aluminum (Al) will be toxic to plants when soil is very acid. Soil reaction on acid condition tends to turn Al into trivalent cation (Al3+) disturbing the function of the root end cells in doing the division and elongating the function. Today, the study of Al stress on crop trees as oil palm is very little. This research was aimed to study the growth of oil palm varieties in growing media treated Al stress. The experiment was conducted in the screen house using a randomized block design with two treatments, oil palm varieties and concentrations of Al. Varieties consisted of five oil palm progenies (OPP) i.e. PPKS239, PPKS540, PPKS718, Simalungun, and Dumpy. They were planted into the sterile sand medium in the form of sprouts and Al was treated with five different concentrations, 0, 75, 150, 225, and 300 ppm. Al was applied at the same time in the plant from 4 to 12 weeks after planting. Observations were conducted on several morphological and physiological variables at shoots and roots. The results showed a significant interaction between varieties and Al on the length of primary roots and reducing sugar content. The average of reducing sugar content was 24% less from control than it was when treated by Al 300 ppm. Simalungun varieties had more tolerant to Al than others. The length of Simalungun primary roots was more stable when the concentration of Al was 300 ppm whereas PPKS718 and PPKS540 varieties were decreased 24.3 and 12.4% respectively. The tolerance of Simalungun was also marked from reducing sugar content which was lower than other varieties. According to Koch (2004) [1], the low content of reducing sugar when given Al was an indication of plant resistance mechanisms against Al toxicity where the number of sugar was transported from roots to the shoots for immobilizing Al. Consequently, it decreased sugar content in the shoot.

The effects of silicon on seed germination and growth parameters of maize seedlings under normal, aluminum (Al), and sodium chloride (NaCl) stress conditions were investigated. The results indicated a dose-dependent relationship between silicon and growth parameters, except for germination attributes.Application of silicon (2 mM) accelerated amylase activity, decreased abscisic acid content, and increased indoleacetic acid and gibberellic acid contents of seedling, The results suggest that the beneficial effects of silicon, at least in part, are mediated by the balance of phytohormones. Exposure to Al (10 mM) significantly decreased all growth parameters of maize seedlings. Application of 2 mM silicon, however, alleviated Al stress and restored almost all growth attributes. Decrease of Al absorption, increase of fructan content, and improvement of amylase activity were considered as the mechanisms of ameliorative function of silicon in Al-stressed maize seedlings. Exposure to silicon, however, did not show beneficial effects on growth parameters of maize seedlings under salt stress conditions. [ABSTRACT FROM PUBLISHER]

The ameliorative effect of H 2 on aluminum (Al)-induced stress remains poorly understood. We treated maize seedlings with Al and hydrogen-rich water (HRW) to determine the roles of H 2 in the alleviation of Al toxicity. Our results demonstrated that Al stress triggered damage to the photosynthetic apparatus, plant growth inhibition, and reactive oxygen species (ROS) production, and boosted lipid peroxidation. However, the addition of HRW at 75% saturation markedly alleviated Al toxicity symptoms through the promotion of root elongation. These responses were related to the significantly increased activities of typical antioxidant enzymes (CAT, APX, SOD, and POD). In vivo imaging of plasma membrane integrity, lipid peroxidation, and the level of ROS provided further evidence that HRW could improve Al tolerance. Our results also indicate that 100% HRW mitigated Al toxicity less than 75% HRW. Moreover, different concentrations of HRW significantly improved photosynthesis and increased nutrient uptake. We conclude that exogenous H 2 supplementation could enhance Al tolerance by reestablishing redox homeostasis and maintaining nutrient homeostasis. [ABSTRACT FROM AUTHOR]

Key message: AtPrx64 is one of the peroxidases gene up-regulated in Al stress and has some functions in the formation of plant second cell wall. Its overexpression may improve plant tolerance to Al by some ways. Studies on its function under Al stress may help us to understand the mechanism of plant tolerance to Al stress. Abstract: In Arabidopsis thaliana, the expressions of some genes ( AtPrxs) encoding class III plant peroxidases have been found to be either up-regulated or down-regulated under aluminum (Al) stress. Among 73 genes that encode AtPrxs in Arabidopsis, AtPrx64 is always up-regulated by Al stress, suggesting this gene plays protective roles in response to such stress. In this study, transgenic tobacco plants were generated to examine the effects of overexpressing of AtPrx64 gene on the tolerance to Al stress. The results showed that overexpression of AtPrx64 gene increased the root growth and reduced the accumulation of Al and ROS in the roots. Compared with wild type controls, transgenic tobaccos had much less soluble proteins and malondialdehyde in roots and much more root citrate exudation. The activity of plasma membrane (PM) H-ATPase, the phosphorylation of PM H-ATPase and its interaction with 14-3-3 proteins increased in transgenic tobaccos; moreover, the content of lignin in root tips also increased. Taken together, these results showed that overexpression of AtPrx64 gene might enhance the tolerance of tobacco to Al stress. [ABSTRACT FROM AUTHOR]

We investigated the influences of exogenous chlorogenic acid (CGA) on the physiological parameters and Al stress-related gene expression of SB(Al-sensitive black soybean)root under Al stress. A major goal of this report was to explore the alleviating molecular mechanism of exogenous CGA on Al toxicity in SB. SB seedings were cultured in water solution and treated with 50 μmol·L-1 Al or CGA plus 50 μmol·L-1 Al. The optimal concentration of CGA alleviating Al toxicity was screened. And we study the effects of optimal exogenous CGA on root tip Al content, the activities of antioxidant enzyme, the expressions of 14-3-3 protein and H+-ATPase, and the activity of H+ pump under 50 μmol·L-1 Al stress. Low concentrations of CGA alleviated inhibition of root elongation caused by Al toxicity and promoted the increase of lateral root numbers under Al stress. However, the CGA-alleviated effect was weaken with high concentration of CGA treatment. It was founded that the alleviation effect of 0.01 g·L-1 CGA was the most significant. Exogenous 0.01 g·L-1 CGA decreased the Al in root tips and MDA contents. And the citric acid content in root exudates of SB under Al stress was significantly increased due to the addition of exogenous 0.01 g·L-1 CGA. Expression analysis showed that exogenous 0.01 g·L-1 CGA enhanced the expression of three 14-3-3 isoforms(14-3-3b, 14-3-3m, and 14-3-3k)and increased the expression of GHA2 (plasma membrane H+-ATPase)gene, but inhibited the gene expression of MATE in SB under Al stress. The results of immunoprecipitation(IP)showed that the phosphorylation of the PM H+-ATPase was up regulated by the exogenous 0.01 g·L-1 CGA, which could bind with 14-3-3 protein under Al stress. Meanwhile, plasma membrane H+-ATPase and H+ pump activities were both enhanced by exogenous 0.01 g·L-1 CGA under Al stress. It was suggested that exogenous CGA may enhance the SB tolerance to Al stress by increasing the lateral roots number, compensating inhibition of MATE expression and interaction between them to increase citric acid exudation. [ABSTRACT FROM AUTHOR]

In this study, Al-sensitive black soybean (Glycine max (L.) Merr.) specimens were treated in Hoagland solutions containing 50-400 μM Al for 1-4 days. The measurement for NO3- uptake showed that the NO3- uptake decreased gradually as the Al concentration and treatment time increased, suggesting that Al stress significantly reduced the NO3- uptake by soybean. Under 100-μM Al stress for 4 days, the plasma membrane (PM) ATPase activity (inorganic phosphate (Pi) release), H+ pump activity, phosphorylation of PM ATPase and its interaction with 14-3-3 protein in soybean root tips were all smaller than those in the root tips of control plants. The addition of 150 μMMg2+ in Al treatment solutions significantly alleviated the Al inhibition of NO3- uptake in soybean. The presence of Mg2+ in a 100-μM Al solution pronouncedly enhanced PM ATPase activity, H+ pump activity, phosphorylation of PM ATPase and its interaction with 14-3-3 protein in soybean root tips. The application of 2μM ascorbic acid (AsA, an H2O2 scavenger) in Al treatment solutions significantly decreased Al-inhibited NO3- uptake in soybean. The cotreatment of soybeans with 2μM AsA and 100 μM Al significantly reduced H2O2 accumulation and increased the PM ATPase activity, H+ pump activity, phosphorylation of PM H+-ATPase and its interaction with 14-3-3 protein in soybean root tips. The evidence suggested that Al-inhibited NO3- uptake is related to Al-increased H2O2 content and Al-decreased phosphorylation of PM ATPase and its interaction with 14-3-3 protein as well as PM ATPase activity in the root tips of soybean. [ABSTRACT FROM AUTHOR]

Recent evidence has proved that caspase protease activities are detected in both mammals and plants during programmed cell death (PCD). The characteristics and functions of caspase-like proteases play important roles in understanding the mechanisms of PCD in plants. In this work, we report firstly the involvement of caspase-like protease activities and effects in aluminum (Al) stress in two contrasting peanut genotypes. Caspase-like activities in the root tip cells of 'Zhonghua 2' (Al-sensitive) and '99-1507' (Al-tolerant) were detected using synthetic caspase substrates during Al-triggered PCD. Caspase-1-, -2-, -3-, -4-, -5-, -6-, -8- and -9-like proteases were found in peanut root tip cells. VDQQDase (caspase-2-like) and WEHD (caspase-5-like) were the first detected in the plants, and almost all of the caspase-like proteases were activated during Al-induced PCD, especially caspase-3-like and caspase-1-like, which was higher in 'Zhonghua 2' than in '99-1507'. The highest activity levels of caspase-3- and caspase-1-like proteases occurred 8 and 4 h after 100 µM Al treatment, respectively. Compared with 100 µM AlCl treatment alone, specific caspase-3 protease inhibitor Ac-DEVD-CHO inhibited the increase of caspase-3-like protease activity, Al content, Hsr203j expression, cell death and DNA fragmentation, and the decrease in root growth induced by 100 µM AlCl treatment, but it was more obvious in 'Zhonghua 2' than in '99-1507'. In conclusion, there were different caspase-like proteases in root tips of peanut, and caspase-3-like protease was a crucial executioner in Al-induced PCD. Its effects in the 'Zhonghua 2' genotype were higher than in '99-1507'. An improved model of the mechanism of Al-induced PCD and Al tolerance differences in different genotypes is proposed. [ABSTRACT FROM AUTHOR]

The ethylene response factor (ERF) transcription factors, which is one of the largest transcription factor families in plants, are involved in biological and abiotic stress response and play an important role in plant growth and development. In this study, the GmABR1 gene from the soybean inbred line Zhonghuang24 (ZH24)×Huaxia 3 (HX3) was investigated its aluminum (Al) tolerance. GmABR1 protein has a conserved domain AP2, which is located in the nucleus and has transcriptional activation ability. The results of real-time quantitative PCR (qRT-PCR) showed that the GmABR1 gene presented a constitutive expression pattern rich in the root tip, stem and leaf tissues of HX3. After Al stress, the GmABR1 transcript was significantly increased in the roots. The transcripts of GmABR1 in the roots of HX3 treated with 50 µM AlCl 3 was 51 times than that of the control. The GmABR1 was spatiotemporally specific with the highest expression levels when Al concentration was 50 µM, which was about 36 times than that of the control. The results of hematoxylin staining showed that the root tips of GmABR1 -overexpression lines were stained the lightest, followed by the control, and the root tips of GmABR1 RNAi lines were stained the darkest. The concentrations of Al 3+ in root tips were 207.40 µg/g, 147.74 µg/g and 330.65 µg/g in wild type (WT), overexpressed lines and RNAi lines, respectively. When AlCl 3 (pH4.5) concentration was 100 µM, all the roots of Arabidopsis were significantly inhibited. The taproot elongation of WT, GmABR1 transgenic lines was 69.6%, 85.6%, respectively. When treated with Al, the content of malondialdehyde (MDA) in leaves of WT increased to 3.03 µg/g, while that of transgenic Arabidopsis increased from 1.66-2.21 µg/g, which was lower than that of WT. Under the Al stress, the Al stress responsive genes such as AtALMT1 and AtMATE , and the genes related to ABA pathway such as AtABI1 , AtRD22 and AtRD29A were up-regulated. The results indicated that GmABR1 may jointly regulate plant resistance to Al stress through genes related to Al stress response and ABA response pathways., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Wang, Li, Wang, Zhong, Xu, Cheng, Nian, Liu, Chen, Zhang and Ma.)

Aluminum (Al) stress in acidic soils has severe negative effects on crop productivity. In this study, the alleviating effect and related mechanism of malate on Al stress in quinoa (Chenopodium quinoa) seedlings were investigated. The findings indicated that malate alleviated the growth inhibition of quinoa seedlings under Al stress, maintained the enzymatic and nonenzymatic antioxidant systems, and aided resistance to the damage caused by excessive reactive oxygen species (ROS). Under Al stress, malate significantly increased the contents of chlorophyll and carotenoids in quinoa shoots by 103.8% and 240.7%, and significantly increased the ratios of glutathione (GSH)/oxidized glutathione (GSSG), and ascorbate (AsA)/dehydroascorbate (DHA) in roots by 59.9% and 699.2%, respectively. However, malate significantly decreased the superoxide radical (O 2 •-), hydrogen peroxide (H 2 O 2), malondialdehyde (MDA) and Al contents in quinoa roots under Al stress by 32.7%, 60.9%, 63.1% and 49%, respectively. Moreover, the CqMADS family and the Al stress-responsive gene families (CqSTOP, CqALMT, and CqWRKY) were identified from the quinoa genome. Comprehensive expression profiling identified CqMADS68 as being involved in malate-mediated Al resistance. Transient overexpression of CqMADS68 increased Al tolerance in quinoa seedlings. More importantly, we found that CqMADS68 regulated the expression of CqSTOP6 , CqALMT6 and CqWRKY88 and further demonstrated the interaction of CqMADS68 with CqSTOP6, CqALMT6 and CqWRKY88 by bimolecular fluorescence complementation (BIFC) experiments. Moreover, transient overexpression and physiological and biochemical analyses demonstrated that CqSTOP6 , CqALMT6 and CqWRKY88 could also improve Al tolerance by maintaining the antioxidant capacity of quinoa seedlings. Taken together, these findings reveal that CqMADS68 , CqSTOP6 , CqALMT6 and CqWRKY88 may be important contributors to the Al tolerance regulatory network in quinoa, providing new insights into Al stress resistance. [Display omitted] • Exogenous application of malate can alleviate quinoa Al toxicity. • CqMADS, CqSTOP, CqALMT and CqWRKY families were identified in quinoa genome. • Malate-mediated CqMADS68 can contribute to Al tolerance in quinoa seedlings. • CqMADS68 improved Al tolerance by interacting with CqSTOP6, CqALMT6 and CqWRKY88. • CqSTOP6, CqALMT6 and CqWRKY88 also contribute to quinoa resistance to Al stress. [ABSTRACT FROM AUTHOR]

Over 40% of arable land in the world is acidic. Al stress has become a global agricultural problem affecting plant growth and limiting crop production in acidic soils. Plants have evolved different regulatory mechanisms of adaptation to exogenous environmental challenges, such as Al stress, by altering their growth patterns. In the past decades, several key genes involved in plant response to Al stress and the mechanism of Al detoxification have been revealed. However, the signaling pathways of plant response to Al stress and the regulatory mechanism of plant Al tolerance remain poorly understood. In this review, we summarized the findings of recent studies on the plant Al tolerance mechanism and the molecular regulation mechanism of phytohormones in response to Al stress. This review improves our understanding of the regulatory mechanisms of plants in response to Al stress and provides a reference for the breeding of Al-tolerant crops.

Micro RNAs (mi RNAs) are a class of regulatory small RNAs ( sRNAs) that down-regulate target genes through mRNA cleavage or translational inhibition. mi RNA is known to play an important role in the root development and environmental responses in both the Arabidopsis and rice. However, little information is available to form a complete view of mi RNAs in the development of the maize root system and Al stress responses in maize. Four sRNA libraries were generated and sequenced from the early developmental stage of primary roots ( PRY), the later developmental stage of maize primary roots ( PRO), seminal roots ( SR) and crown roots ( CR). Through integrative analysis, we identified 278 mi RNAs (246 conserved and 32 novel ones) and found that the expression patterns of mi RNAs differed dramatically in different maize roots. The potential targets of the identified conserved and novel mi RNAs were also predicted. In addition, our data showed that CR is more resistant to Al stress compared with PR and SR, and the differentially expressed mi RNAs are likely to play significant roles in different roots in response to environmental stress such as Al stress. Here, we demonstrate that the expression patterns of mi RNAs are highly diversified in different maize roots. The differentially expressed mi RNAs are correlated with both the development and environmental responses in the maize root. This study not only improves our knowledge about the roles of mi RNAs in maize root development but also reveals the potential role of mi RNAs in the environmental responses of different maize roots. [ABSTRACT FROM AUTHOR]

Aluminum (Al) stress is a major factor limiting crop production. The primary symptom of Al toxicity is to inhibit root growth. Plant responses to Al require precise regulation of gene expression at transcriptional and post-transcriptional levels. MicroRNAs (miRNAs) are 20-23 nucleotides length non-coding RNAs, which promote the cleavage of target mRNAs. We have summarized some Al-responsive miRNAs identified, especially proposed the regulatory roles of miR319, miR390, miR393, miR319a.2, and miR398 in Al stress signaling network. The cross-talk between miRNAs and signaling pathways also has been discussed. [ABSTRACT FROM AUTHOR]

Abstract: To understand the ecology and physiology of metal-accumulating lichens growing in Cu-polluted sites, we investigated lichens near temple and shrine buildings with Cu roofs in Japan and found that Stereocaulon japonicum Th. Fr. and Cladonia humilis (With.) J. R. Laundon grow in Cu-polluted sites. Metal concentrations in the lichen samples collected at some of these sites were determined by inductively coupled plasma mass spectroscopy (ICP-MS). UV–vis absorption spectra of pigments extracted from the lichen samples were measured, and the pigment concentrations were estimated from the spectral data using equations from the literature. Secondary metabolites extracted from the lichen samples were analyzed by high-performance liquid chromatography (HPLC) with a photodiode array detector. We found that S. japonicum and C. humilis are Cu-hyperaccumulating lichens. Differences in pigment concentrations and their absorption spectra were observed between the Cu-polluted and control samples of the 2 lichens. However, no correlation was found between Cu and pigment concentrations. We observed a positive correlation between Al and Fe concentrations and unexpectedly found high negative correlations between Al and pigment concentrations. This suggests that Al stress reduces pigment concentrations. The concentrations of secondary metabolites in C. humilis growing in the Cu-polluted sites agreed with those in C. humilis growing in the control sites. This indicates that the metabolite concentrations are independent of Cu stress. [Copyright &y& Elsevier]