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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: In the past few decades, microalgae biofuel has become one of the most interesting sources of renewable energy. However, the higher cost of microalgae biofuel compared to that of petroleum prevented microalgae biofuel production. Therefore, the research on increasing lipid productivity from microalgae becomes more important. The lipid production source, triacylglycerol biosynthesis in microalgae requires short chain fatty acids as substrates, which are synthesized in chloroplasts. However, the transport mechanism of fatty acids from microalgae chloroplasts to cytosol remains unknown. Results: cDNAs from two homologs of the Arabidopsis fatty acid exporter 1 (FAX1) were cloned from Chlamydomonas reinhardtii and were named crfax1 and crfax2. Both CrFAXs were involved in fatty acid transport, and their substrates were mainly C16 and C18 fatty acids. Overexpression of both CrFAXs increased the accumulation of the total lipid content in algae cells, and the fatty acid compositions were changed under normal TAP or nitrogen deprivation conditions. Overexpression of both CrFAXs also increased the chlorophyll content. The MGDG content was decreased but the TAG, DAG, DGDG and other lipid contents were increased in CrFAXs overexpression strains. Conclusion: These results reveal that CrFAX1 and CrFAX2 were involved in mediating fatty acid export for lipids biosynthesis in C. reinhardtii. In addition, overexpression of both CrFAXs obviously increased the intracellular lipid content, especially the triacylglycerol content in microalgae, which provides a potential technology for the production of more biofuels using microalgae. [ABSTRACT FROM AUTHOR]