Search

Background and aims: Although phytolith analysis is a promising tool for reconstructing the palaeovegetation in grassland ecosystems, no phytolith study has yet attempted to quantitatively reconstruct the corresponding plant community characteristics. Questions remain regarding whether or not soil phytoliths can quantitatively reflect various aspects of grassland physiognomy, and how well modern phytoliths represent the quantitative characteristics of grassland ecosystems. These are important scientific issues in the field of phytolith analysis, which require further research on the modern phytoliths of grassland ecosystems. Methods: In order to explore the potential of phytolith analysis in the temperate grassland region, we have for the first time established a modern soil phytolith reference dataset by exploring the relationships between soil phytoliths and plant species inventory data from 77 sites in the Songnen grassland in Northeast China. Results: The results show that phytolith assemblages can clearly distinguish Leymus chinensis grassland, Stipa grassland and mesophytic herb grassland. In addition, we found that the Ic phytolith index could discriminate samples of L. chinensis grassland from the other samples, while the Iph phytolith index proved to be less reliable in the region. In addition, in terms of quantitative plant community characteristics, the soil phytoliths showed a good correspondence with plant community cover and species richness, but not with biomass and diversity index. The transfer functions established in this study can provide reliable estimates of community cover and species richness in the Songnen grassland. In addition, phytoliths are shown to have the potential to reconstruct the taxonomic abundance of the aboveground plant community. Conclusion: This study is a major advance in the application of phytolith analysis to the quantitative estimation of plant community characteristics, and it provides a modern phytolith reference for the quantitative reconstruction of the paleovegetation of grassland ecosystems. [ABSTRACT FROM AUTHOR]

Aims: Populus can tolerant high concentration Al stress. However, the mechanisms of Mg alleviation to Al toxicity in populus remain unknown. Methods: In the present study, adequate Mg was supplied to poplar under high concentration Al toxicity stress, and the pH gradients of root surface, Mg and Al uptake from root apex were detected using electrophysiological analysis, fluorescence staining, etc. Furthermore, auxin distribution and transport dynamic kinetics in root tips were also detected. Results: In the present study, we found that adequate supply of Mg alleviated high concentration Al toxicity to populus root growth. Mg promoted the pH gradients of root surface in populus, leading to alkalization in the root transition zone, which prevented Al toxicity to root elongation. The auxin distribution in root tips of populus was detected using DR5:GFP reporter. The transport and distribution of polar auxin in root transition zone were inhibited by Al toxicity, but partially alleviated by Mg supply. Further electrophysiological experiments using auxin transporter mutant pin-formed 2 (pin2) showed that Mg alleviated Al toxicity by PIN2-based polar auxin transport, which regulated root surface alkalization in the transition zone. Transcriptomic analysis and yeast complementation experiments using mrs2 mutants also reveals same relationships among Mg, auxin and Al. Conclusions: The present study suggests that Mg promotes polar auxin transport and distribution, which leads to the elevated root surface pH regulation, and further alleviates the Al toxicity. Our results partially clarify the mechanism of Mg in alleviating the toxicity of high concentration Al in woody plants. [ABSTRACT FROM AUTHOR]

Background and aims: Magnesium (Mg) deficiency impacts many metabolic processes in Brassica napus (B. napus), leading to yield loss. However, the mechanism of Mg2+ uptake and translocation in B. napus remains unknown. Methods: After screening 39 genotypes of B. napus under Mg-deficient conditions, the cultivars P160 and P153 were selected according to their Mg transfer factor (TF) from root to shoot. We further characterized these two genotypes under Mg-deficiency by analyzing chlorophyll concentration, malondialdehyde and peroxidase activity, and reducing sugar concentration in leaves. Additionally, we performed transcriptomics and qRT-PCR assays on P153 and P160 shoots and roots. The identified functional genes involved in Mg transport were characterized by functional assays in yeast and Arabidopsis mutants. Results: The physiological analysis revealed that P160 (Mg tolerance cultivar; Mg-T) is more tolerant than P153 (Mg sensitive cultivar; Mg-S) under magnesium-deficient environments. Transcriptomics and qRT-PCR assays revealed that transcript levels of BnMGT1–2 and BnMGT6–1 were more significantly up-regulated in the shoot of Mg-T cultivar than that of the Mg-S cultivar under Mg limitation. Functional assays of BnMGT1–2 and BnMGT6–1 reveals that BnMGT1–2 and BnMGT6–1 are the two main functional Mg transporters mediating Mg translocation from root to shoot under low Mg conditions. Conclusion: Mg-T is more efficient in the translocation of Mg from root to shoot than Mg-S. BnMGT1–2 and BnMGT6–1 should be the two main Mg transporters associated with Mg translocation under Mg deficiency condition, which caused the different Mg efficiency between the Mg-T and Mg-S. [ABSTRACT FROM AUTHOR]

Aims: Cadmium (Cd) is the most widespread toxic heavy metal to plant growth. As the second leading oil crop, some genotypes of Brassica napus (B. napus) are potential Cd accumulators. However, the Cd translocation mechanism from root to shoot in B. napus in response to Cd toxicity remains unknown. Methods: In the present study, a couple of B. napus genotypes with contrasting Cd uptake and root-to-shoot translocation abilities, named P78 (the high Cd accumulator, HC) and P72 (the low Cd accumulator, LC), were chosen from 39 B. napus genotypes with various Cd accumulation features. Results: Physiological comparison of P78 and P72 reveals that P72 is more sensitive to Cd toxicity than P78. With genomic resequencing, transcriptomics and qRT-PCR assay, BnNramp2;1 and BnNramp4;2 were focused with highly upregulation in shoot of P78 under Cd treatment condition. Furthermore, BnNramp2;1 and BnNramp4;2 can successfully complement the function of tonoplast localized Cd transporter YCF1. And when BnNramp2;1 and BnNramp4;2 were transferred in Arabidopsis atnramp mutants, the transgenic plants showed better growth rate than mutants under higher Cd stress conditions. Conclusions: The results reveals that BnNramp2;1 and BnNramp4;2 were two main Cd transporters associated with enhanced root-to-shoot translocation and accumulation of Cd in shoot of B. napus. [ABSTRACT FROM AUTHOR]

Background and aims: Brassica napus (B. napus), one of the most important oil crop species, is highly tolerant to and accumulates high amounts of cadmium (Cd). Many iron transporters in plants have been identified to be Cd transporters. For example, some members of the heavy metal P1B-ATPase transporter family are responsible for Cd translocation in various plant species and play a vital role in Cd detoxification. However, the Cd translocation mechanism in B. napus and the characterization of the heavy metal ATPase (HMA) in B. napus remain unknown.Methods: B. napus plants were treated with 50 μM or 200 μM Cd in soil for 30 days during the initial flowering stage. The dry weight of the plants and the Cd contents within their various tissues were then measured, after which the RNA in the leaves was extracted for transcriptomic analysis and subsequent quantitative real-time PCR (qRT-PCR) assays. After all the significantly regulated iron transporters were screened in response to Cd stress, the BnHMA gene family was identified and shown to link BnHMA genes with Cd translocation in the leaves of B. napus.Results: The transcriptomic analysis of B. napus leaves in response to Cd treatment revealed that several HMA genes (BnHMA2;2, BnHMA2;3 and BnHMA2;5) respond to Cd stress. We further examined the whole HMA family in B. napus; 31 BnHMA genes were subsequently identified. Their expression levels in different tissues and stages as well as their phylogenetic tree, gene structure, chromosomal location, conserved motifs, 3D models and subcellular localization were analyzed. The results showed that these HMA genes exhibit typical characteristics of HMA genes. In addition, the qRT-PCR results showed that the BnHMA2;3 expression levels in the B. napus plants treated with 50 μM or 200 μM Cd were seven- and ninefold greater than those under Cd-free conditions, respectively. Additional yeast experiment assays verified that BnHMA2;3 can transport Cd.Conclusion: BnHMA2;3 may play an important role in Cd translocation in the leaves of B. napus. The results of this study may provide direction and useful information for increased understanding of the Cd stress-response mechanism. [ABSTRACT FROM AUTHOR]

Aims: Phosphorus (P) is essential for Brassica napus L. (B. napus) growth and development, but most P in soil is unavailable. Evidence shows that BnaPHT1s react to a range of nutritional stresses and heavy metals. However, little is known about the mechanism of BnaPHT1s in B. napus. Therefore, the present study aimed to characterize the members of the BnaPHT1 in allotetraploid B. napus and to analyze their expression profile in response to environmental stresses. BnaPHT1;4 J is a member of the little-known mechanism in this regard. We used Xiaoyun (XY) to investigate the effect of BnaPHT1;4 J on phosphate (Pi) uptake.In this study, we identified a novel member of PHT1;4 subfamily in B. napus, which is highly expressed in root under low Pi stress, and named it BnaPHT1;4 J. We further characterized the role of BnaPHT1;4 J for Pi uptake in B. napus. Quantitative RT-PCR, onion subcellular localization, and GUS expression analysis reveal that BnaPHT1;4 J is a membrane protein that is mainly localized at roots under low Pi conditions.Phenotypic characterization showed that BnaPHT1;4 J overexpression under low Pi promoted root growth and main root elongation in Arabidopsis and B. napus, and other physiological indicators such as P content and biomass in B. napus were also positively regulated.BnaPHT1;4 J has a catalytic effect on seedlings and nutritional growth of B. napus and promotes Pi uptake and translocation.Methods: Phosphorus (P) is essential for Brassica napus L. (B. napus) growth and development, but most P in soil is unavailable. Evidence shows that BnaPHT1s react to a range of nutritional stresses and heavy metals. However, little is known about the mechanism of BnaPHT1s in B. napus. Therefore, the present study aimed to characterize the members of the BnaPHT1 in allotetraploid B. napus and to analyze their expression profile in response to environmental stresses. BnaPHT1;4 J is a member of the little-known mechanism in this regard. We used Xiaoyun (XY) to investigate the effect of BnaPHT1;4 J on phosphate (Pi) uptake.In this study, we identified a novel member of PHT1;4 subfamily in B. napus, which is highly expressed in root under low Pi stress, and named it BnaPHT1;4 J. We further characterized the role of BnaPHT1;4 J for Pi uptake in B. napus. Quantitative RT-PCR, onion subcellular localization, and GUS expression analysis reveal that BnaPHT1;4 J is a membrane protein that is mainly localized at roots under low Pi conditions.Phenotypic characterization showed that BnaPHT1;4 J overexpression under low Pi promoted root growth and main root elongation in Arabidopsis and B. napus, and other physiological indicators such as P content and biomass in B. napus were also positively regulated.BnaPHT1;4 J has a catalytic effect on seedlings and nutritional growth of B. napus and promotes Pi uptake and translocation.Results: Phosphorus (P) is essential for Brassica napus L. (B. napus) growth and development, but most P in soil is unavailable. Evidence shows that BnaPHT1s react to a range of nutritional stresses and heavy metals. However, little is known about the mechanism of BnaPHT1s in B. napus. Therefore, the present study aimed to characterize the members of the BnaPHT1 in allotetraploid B. napus and to analyze their expression profile in response to environmental stresses. BnaPHT1;4 J is a member of the little-known mechanism in this regard. We used Xiaoyun (XY) to investigate the effect of BnaPHT1;4 J on phosphate (Pi) uptake.In this study, we identified a novel member of PHT1;4 subfamily in B. napus, which is highly expressed in root under low Pi stress, and named it BnaPHT1;4 J. We further characterized the role of BnaPHT1;4 J for Pi uptake in B. napus. Quantitative RT-PCR, onion subcellular localization, and GUS expression analysis reveal that BnaPHT1;4 J is a membrane protein that is mainly localized at roots under low Pi conditions.Phenotypic characterization showed that BnaPHT1;4 J overexpression under low Pi promoted root growth and main root elongation in Arabidopsis and B. napus, and other physiological indicators such as P content and biomass in B. napus were also positively regulated.BnaPHT1;4 J has a catalytic effect on seedlings and nutritional growth of B. napus and promotes Pi uptake and translocation.Conclusions: Phosphorus (P) is essential for Brassica napus L. (B. napus) growth and development, but most P in soil is unavailable. Evidence shows that BnaPHT1s react to a range of nutritional stresses and heavy metals. However, little is known about the mechanism of BnaPHT1s in B. napus. Therefore, the present study aimed to characterize the members of the BnaPHT1 in allotetraploid B. napus and to analyze their expression profile in response to environmental stresses. BnaPHT1;4 J is a member of the little-known mechanism in this regard. We used Xiaoyun (XY) to investigate the effect of BnaPHT1;4 J on phosphate (Pi) uptake.In this study, we identified a novel member of PHT1;4 subfamily in B. napus, which is highly expressed in root under low Pi stress, and named it BnaPHT1;4 J. We further characterized the role of BnaPHT1;4 J for Pi uptake in B. napus. Quantitative RT-PCR, onion subcellular localization, and GUS expression analysis reveal that BnaPHT1;4 J is a membrane protein that is mainly localized at roots under low Pi conditions.Phenotypic characterization showed that BnaPHT1;4 J overexpression under low Pi promoted root growth and main root elongation in Arabidopsis and B. napus, and other physiological indicators such as P content and biomass in B. napus were also positively regulated.BnaPHT1;4 J has a catalytic effect on seedlings and nutritional growth of B. napus and promotes Pi uptake and translocation. [ABSTRACT FROM AUTHOR]