Cloning and Functional Characterization of SpZIP2

Transcriptomic Analysis Reveals the Mechanisms of Cadmium Transport and Detoxification in Portuguese Oysters (Crassostrea angulata)

Oysters are a globally distributed aquatic economic shellfish with a remarkable ability to accumulate cadmium (Cd). The phenomenon of Cd content exceeding safety standards in oysters occurs frequently, posing a significant risk to food safety. In this study, Portuguese oysters (Crassostrea angulata) were exposed to 2 μg/L of Cd for 15 days. Individuals with significantly different Cd accumulation were selected for transcriptomic sequencing analysis. KEGG enrichment analysis revealed that the differentially expressed genes (DEGs) between high- and low-Cd-accumulation individuals, as well as those before and after Cd exposure, were primarily enriched in metabolic pathways (33.8%) and organismal systems (32.2%). ABC transporters, phagosomes, glutathione metabolism, and the biosynthesis of amino acids played crucial roles in Cd accumulation and detoxification processes. Metal cation transport-related genes, including zip1, copt5.1, and orct2, may be involved in the Cd transport process in Portuguese oysters, and their differential expression influences Cd accumulation in the soft tissues. Meanwhile, genes such as sod3, cyp4f22, and abca3 are likely to play significant roles in detoxification under Cd exposure. Additionally, alternative splicing analysis identified 13 potential genes associated with Cd response in Portuguese oysters, including cs2, gfpt1, and acox1.

The Ammonium Transporter SpAMT1;2 Contributes to Nitrogen Utilisation and Cadmium Accumulation in the Hyperaccumulator Sedum Plumbizincicola

Sedum plumbizincicola (Sp) is a cadmium (Cd) hyperaccumulator found specifically in abandoned ancient mines where N is regularly deficient while Cd presents in excess. How Sp got adapted to this unique habitat remains unknown. Here, we reported relative abundant presence of NH4 + in mine areas for Sp, and the isolation and functional characterisation of a putative NH4 + transporter gene AMT1;2, which is highly expressed in Sp roots and encodes a pH-dependent dual affinity ammonium uptake transporter. Compared to SaAMT1;2, the homologous gene in the nonhyperaccumulating control Sedum alfredii (Sa), SpAMT1;2 expression is much higher and not inhibited by Cd. Only eight amino acid sequence polymorphisms were observed between SpAMT1;2 and SaAMT1;2, and the in-vitro NH4 + uptake activity and subcellular localisation are identical between them with or without Cd stress. Moreover, in contrast in Sa, NH4 + uptake in Sp is not inhibited by Cd, and NH4 + at ambient level promotes Cd accumulation. These data suggest that SpAMT1;2 is likely an essential gene contributing to nitrogen nutrition and the interaction between NH4 +and Cd uptake in Sp, which might represent a novel N utilisation pathway evolved in mines for the hyperaccumulator Sp.

NnMTP10 from Nelumbo nucifera acts as a transporter mediating manganese and iron efflux

Deficiency or excess of mineral elements in the environment is a primary factor limiting crop yields and nutritional quality. Lotus (Nelumbo nucifera) is an important aquatic crop in Asia, but the mechanism for accumulating mineral nutrients and coping with nutrient deficiency/excess is still largely unknown. Here, we identified NnMTP10, a member of the cation diffusion facilitator family, by screening the cDNA library of lotus. Subcellular localization to the plasma membrane, increased manganese (Mn) and iron (Fe) tolerance and reduced metal accumulation in yeast transformants demonstrated that the protein functions as an exporter to mediate the efflux of Mn and Fe. Arabidopsis overexpressing NnMTP10 exhibited less Mn accumulation in roots, increased long-distance transport to shoots, and increased tolerance to Mn stress under high-Mn conditions. However, the accumulation and tolerance of Fe in Arabidopsis transformants are opposite to those of Mn. Further analysis revealed that excessive Fe in the root apoplast exported by NnMTP10 was sequestrated by the cell wall, thereby reducing the transport of Fe to the shoot. Correspondingly, the expression of NnMTP10 in the roots of lotus was increased under the high-Mn treatment but decreased under the high-Fe treatment. These results suggest that NnMTP10 is involved in the long-distance transport of Mn and Fe in lotus and may play a role in coordinating the adaptation to stresses caused by excessive Mn and Fe.

Interaction between Boron and Other Elements in Plants

Boron (B) is an essential mineral nutrient for growth of plants, and B deficiency is now a worldwide problem that limits production of B deficiency-sensitive crops, such as rape and cotton. Agronomic practice has told that balanced B and other mineral nutrient fertilizer applications is helpful to promote crop yield. In recent years, much research has reported that applying B can also reduce the accumulation of toxic elements such as cadmium and aluminum in plants and alleviate their toxicity symptoms. Therefore, the relation between B and other elements has become an interesting issue for plant nutritionists. Here we summarize the research progress of the interaction between B and macronutrients such as nitrogen, phosphorus, calcium, potassium, magnesium, and sulfur, essential micronutrients such as iron, manganese, zinc, copper, and molybdenum, and beneficial elements such as sodium, selenium, and silicon. Moreover, the interaction between B and toxic elements such as cadmium and aluminum, which pose a serious threat to agriculture, is also discussed in this paper. Finally, the possible physiological mechanisms of the interaction between B and other elements in plants is reviewed. We propose that the cell wall is an important intermediary between interaction of B and other elements, and competitive inhibition of elements and related signal transduction pathways also play a role. Currently, research on the physiological role of B in plants mainly focuses on its involvement in the structure and function of cell walls, and our understanding of the details for interactions between B and other elements also tend to relate to the cell wall. However, we know little about the metabolic process of B inside cells, including its interactions with other elements. More research is needed to address the aforementioned research questions in future.