A defensin-like protein drives cadmium efflux and allocation in rice.

Pollution by heavy metals limits the area of land available for cultivation of food crops. A potential solution to this problem might lie in the molecular breeding of food crops for phytoremediation that accumulate toxic metals in straw while producing safe and nutritious grains. Here, we identify a rice quantitative trait locus we name cadmium (Cd) accumulation in leaf 1 (CAL1), which encodes a defensin-like protein. CAL1 is expressed preferentially in root exodermis and xylem parenchyma cells. We provide evidence that CAL1 acts by chelating Cd in the cytosol and facilitating Cd secretion to extracellular spaces, hence lowering cytosolic Cd concentration while driving long-distance Cd transport via xylem vessels. CAL1 does not appear to affect Cd accumulation in rice grains or the accumulation of other essential metals, thus providing an efficient molecular tool to breed dual-function rice varieties that produce safe grains while remediating paddy soils.

Molecular and functional characterization of a novel CD302 gene from ayu (Plecoglossus altivelis).

Recognizing the presence of invading pathogens by pattern recognition receptors (PRRs) is key to mounting an effective innate immune response. Mammalian CD302 is an unconventional C-type lectin like receptor (CTLR) involved in the functional regulation of immune cells. However, the role of CD302 in fish remains unclear. In this study, we characterized a novel CD302 gene from ayu (Plecoglossus altivelis), which was tentatively named PaCD302. The cDNA sequence of PaCD302 is 1893 nucleotides in length, and encodes a polypeptide of 241 amino acids with molecular weight 27.1 kDa and pI 4.69. Sequence comparison and phylogenetic tree analysis showed that PaCD302 is a type I transmembrane CTLR devoid of the known amino acid residues essential for Ca(2+)-dependent sugar binding. PaCD302 mRNA expression was detected in all tissues and cells tested, with the highest level in the liver. Following Vibrio anguillarum infection, PaCD302 mRNA expression was significantly upregulated in all tissues tested. For further functional analysis, we generated a recombinant protein for PaCD302 (rPaCD302) by prokaryotic expression and raised a specific antibody against rPaCD302. Western blot analysis revealed that the native PaCD302 is glycosylated. Refolded rPaCD302 was unable to bind to five monosaccharides (l-fucose, d-galactose, d-glucose, d-mannose and N-acetyl glucosamine) or two other polysaccharides (lipopolysaccharide and peptidoglycan). It was able to bind to three Gram-positive and seven Gram-negative bacteria, but show no bacterial agglutinating activity. PaCD302 function blocking using anti-PaCD302 IgG resulted in inhibition of phagocytosis and bactericidal activity of ayu monocytes/macrophages (MO/MΦ), suggesting that PaCD302 regulates the function of ayu MO/MΦ. In summary, our study demonstrates that PaCD302 may participate in the immune response of ayu against bacterial infection via modulation of MO/MΦ function.

A transmembrane C-type lectin receptor mediates LECT2 effects on head kidney-derived monocytes/macrophages in a teleost, Plecoglossus altivelis.

Leukocyte cell-derived chemotaxin 2 (LECT2) is a multifunctional cytokine involved in many diseases in which immune dysfunction is present. Ayu LECT2 (PaLECT2), which interacts with a C-type lectin receptor (PaCLR), was shown to activate ayu head kidney-derived monocytes/macrophages (MO/MΦ) to improve the outcomes of fish upon bacterial infections. However, it is not known if PaCLR mediates PaLECT2 effects on ayu MO/MΦ. In this study, we determined the role of PaCLR in signal transduction of PaLECT2 on ayu MO/MΦ. We expressed the PaCLR ectodomain in Escherichia coli and produced a refolded recombinant protein (rPaCLR) that was then used to produce the anti-PaCLR IgG (anti-PaCLR) for neutralization. Addition of the refolded PaLECT2 mature peptide (rPaLECT2m) to ayu MO/MΦ cultures, increased cytokine expression, induced chemotaxis, and enhanced phagocytosis and bactericidal activity of these cells were observed. When we added anti-PaCLR to block the ectodomain of PaCLR, these effects were significantly inhibited. Based on our previous works and the data presented here, we conclude that PaCLR mediates the immunomodulatory effects of PaLECT2 on ayu MO/MΦ, thus defining a mechanism by which LECT2 protects fish against pathogens.

[Effects of planting density and nitrogen application rate on soil microbial activity under wheat/forage rape multiple cropping].

A field experiment was conducted to study the effects of planting density and nitrogen application rate on the topsoil (0-15 cm) microbial activity under wheat/forage rape multiple cropping. The results showed that multiple-cropping forage rape with wheat could significantly increase soil microbial biomass C (Cmic), soil microbial biomass N (Nmic), soil bacteria number (SBN), soil fungi number (SFN) and soil actinomyces number (SAN), but decrease soil microbial biomass C/N (Cmic/Nmic). The Cmic/Nmic and SBN increased with increasing planting density of forage rape, while Nmic and SAN were in adverse. SFN increased significantly with increasing nitrogen application rate, but Cmic and Nmic decreased first, increased then, and decreased again, with the highest in treatment 1000 kg x hm(-2) N. Also with increasing nitrogen application rate, the SFN and SAN during harvest stage of forage rape decreased first and increased then, while the SAN during seedling stage increased first and decreased then. Soil microbial activities at rape harvest stage were all higher than those at seedling stage, except for SAN in treatment 600 kg x hm(-2) N. SBN and SAN were positively correlated with Cmic and Nmic, but negatively correlated with/Nmic. No significant correlation was observed between SFN and Cmic, and SMBN and Cmic/Nmic.