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Physiological and transcriptomic analyses reveal sulfur is essential for cadmium detoxification and accumulation in poplar leaves

ABSTRACT: Although poplars are good candidates for the phytoremediation of cadmium (Cd)-polluted soils and sulfur is a key player in modulating Cd detoxification and accumulation in plants, the physiological and molecular mechanisms underlying sulfur-mediated Cd accumulation remain largely unknown. To investigate physiological and transcriptomic regulation mechanisms of poplars in response to Cd exposure and different sulphate (S) supply levels, Populus deltoides saplings were exposed to either 0 or 50 µM Cd together with one of low, moderate and high S levels. Cd was accumulated in the leaves of Cd-exposed poplars under moderate S condition, and its accumulation is inhibited by low S but tended to increase by high S. Sulfur nutrition became deficient in Cd-treated leaves, and it was aggravated by low S but improved by high S. Concentrations of cysteine and glutathione were increased in Cd-treated leaves, and the Cd-induced increases were limited by low S but stimulated by high S. In line with the physiological changes, a number of mRNAs and microRNAs (miRNAs) involved in Cd accumulation and sulfur assimilation were identified and the miRNAs-mRNAs networks were dissected. In the networks, miR395 and miR399 members were identified as hub miRNAs and their targets were ATP sulfurylase 3 (ATPS3), and phosphate 2 (PHO2) and beta galactosidase 1 (BGAL1), respectively. These results suggest that Cd-induced changes in Cd accumulation and sulfur assimilation are exacerbated by low S but alleviated by high S supply, and that miRNAs-mRNAs regulatory networks play pivotal roles in sulfur-mediated Cd detoxification and accumulation in poplars.

ORGANISM(S): Populus deltoides

PROVIDER: GSE142565 | GEO | 2021/05/31

REPOSITORIES: GEO

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Project description:The metabolic response of maize source leaves to low nitrogen supply was analyzed in maize seedlings by parallel measurements of transcriptome and metabolome profiling. Inbred lines A188 and B73 were cultivated under controlled growth chamber conditions and supplied with either sufficient (15mM) or limiting (0.15mM) nitrate supply. Leaf lamina material was harvested at day 20 and day 30 after germination with the fifth and sixth leaf representing the main source leaf respectively. Four replicates were collecetd from individual plants for each combination of genotype, growth stage and nitrogen treatment. The leaf material was frozen, homogenised and aliquoted for transcriptome and metabolome analysis. The molecular data was further supplemented by phenotypic characterisation of the maize seedlings under investigation. Limited availability of nitrogen caused strong shifts in the metabolite profile of leaves. The transcriptome was less affected by the nitrogen stress but showed strong genotype and age dependent patterns. Nitrogen starvation initiated the selective down-regulation of processes involved in nitrate reduction and amino acid assimilation; ammonium assimilation related transcripts on the other hand were not influenced. Carbon assimilation related transcripts were characterized by high transcriptional coordination and general down-regulation under low nitrogen conditions. Nitrogen deprivation caused a slight accumulation of starch, but also directed increased amounts of carbohydrates into the cell wall and secondary metabolites. The decrease in N availability also resulted in accumulation of phosphate and by strong down-regulation of genes usually involved in phosphate starvation response, underlining the great importance of phosphate homeostasis control under stress conditions. Maize inbred lines A188 and B73 were cultivated in pots containing nutrient poor peat soil under the controlled conditions of a growth chamber. The plants were fertilized with modified Hoagland solutions containing either 15mM (high N) or 0.15mM nitrate (low N). Source leaf lamina were harvested at day 20 and day 30 after start of germination for parallel analysis of transcriptome and metabolome profiles. The molecular data is further supplemented by phenotypic characterization of the maize seedlings under investigation.

Project description:Boron (B) is an essential nutrient for normal growth of plants. Despite its low abundance in soils, B pollution and toxicity have been reported to increase in especially arid and semi-arid environments. Poplars are known to be tolerant species to B toxicity and accumulation. In the current study, physiological, transcriptomic and hormonal regulations behind B toxicity response were investigated comparatively in poplar species. Previously identified clones of Populus nigra (P.n) and Populus alba (P.a) having contrasting B accumulation and leaf B toxicity symptoms were treated with elevated soil B supply in a pot trial. The physiological results of treatment indicated better biomass growth, higher leaf chlorophyll content and more than three folds lower B accumulation in leaves of P.a compared to P.n. Microarray based transcriptomic analysis revealed 1902 and 1006 differentially regulated transcripts for the leaves and roots of P.a, respectively. Several transcripts responsible in salicylic acid (SA) production (salicylic acid binding protein 2) and SA dependent gene regulation (chitinases, proteases, lipases and protease inhibitors) were strongly upregulated specifically in P.a tissues under B toxicity. Furthermore, endogenous SA content in the roots and leaves of P.a increased with a soil B concentration-dependent manner while there was no significant alteration in the same hormone for P.n tissues under B toxicity. Therefore, increase in endogenous SA concentration was strongly attributed to lower B uptake and B toxicity tolerance in P.a. In addition to SA mediated gene regulation, genes responsible in external excretion process was also supposed to be functional in P.a for reduction of tissue B content under toxic conditions. On the other hand, transcriptome profiling of P.n under B toxicity revealed 1624 and 1419 altered transcripts for the leaves and roots, respectively. Specific induction in transcripts annotated to ATP binding cassette B type transporters, glutathione S transferases and metallochaperones in P.n were linked to internal excretion of excess B in the species that could be related with much higher B uptake from the roots, directional transport to the leaves and detoxification under toxic B conditions.

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Physiological and transcriptomic analyses reveal sulfur is essential for cadmium detoxification and accumulation in poplar leaves

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