Lead and cadmium tolerance and accumulation of proanthocyanidin- deficient mutants of the fern Athyrium yokoscense

The fern Athyrium yokoscense often flourishes around mine sites in Japan and can tolerate and accumulate heavy metals such as lead (Pb) and cadmium (Cd). In this work, we examined whether proanthocyanidins, also called condensed tannins, were involved in the mechanisms of Pb and Cd tolerance and accumulation of A. yokoscense because proanthocyanidins are known to alleviate metal stress in several plant species and are present at high levels in A. yokoscense. For this purpose, we used mutant gametophytes deficient in proanthocyanidins, in which the relative proanthocyanidin contents were 20% of those of the wild-type gametophytes. Although the proanthocyanidin contents of the mutant were quite low, the growth of the mutant was very similar to that of the wild-type gametophytes even in the presence of 80 mg/kg Pb or 48 mg/kg Cd. Under the same conditions, the mutant gametophytes also accumulated Pb and Cd as much as the wild-type gametophytes did. These results indicate that the proanthocyanidins in A. yokoscense are not important for the Pb and Cd tolerance and accumulation properties.

The elemental defense effect of cadmium on Alternaria brassicicola in Brassica juncea

Background The elemental defense hypothesis states a new defensive strategy that hyperaccumulators defense against herbivores or pathogens attacks by accumulating heavy metals. Brassica juncea has an excellent ability of cadmium (Cd) accumulation. However, the elemental defense effect and its regulation mechanism in B. juncea remain unclear. Results In this study, we profiled the elemental defense effect and the molecular regulatory mechanism in Cd-accumulated B. juncea after Alternaria brassicicola infection. B. juncea treated with 180 mg Kg− 1 DW CdCl2 2.5H2O exhibited obvious elemental defense effect after 72 h of infection with A. brassicicola. The expression of some defense-related genes including BjNPR1, BjPR12, BjPR2, and stress-related miRNAs (miR156, miR397, miR398a, miR398b/c, miR408, miR395a, miR395b, miR396a, and miR396b) were remarkably elevated during elemental defense in B. juncea. Conclusions The results indicate that Cd-accumulated B. juncea may defend against pathogens by coordinating salicylic acid (SA) and jasmonic acid (JA) mediated systemic acquired resistance (SAR) and elemental defense in a synergistic joint effect. Furthermore, the expression of miRNAs related to heavy metal stress response and disease resistance may regulate the balance between pathogen defense and heavy metal stress-responsive in B. juncea. The findings provide experimental evidence for the elemental defense hypothesis in plants from the perspectives of phytohormones, defense-related genes, and miRNAs.

Biogeochemistry of Dominant Plants and Soils in Shewushan Gold Lateritic Deposit, China

This paper describes the effect of mineral elements on dominant plants in the Shewushan lateritic gold deposit, China. For this purpose, 30 soil profile samples at different depths and 3 kinds of dominant plants including Populus canadensis (Populus X canadensis Moench), Cinnamomun camphora (Cinnamomum camphora (L.) Presl.) and Rhus chinensis (Rhus chinensis Mill.) were collected. The concentration of ore-forming elements including Au, Ag, Pb, Zn, Cu, As, Fe, and S were analyzed. Based on the investigation of two mine profiles, it can be found that Au, Pb, As, and Fe were mainly enriched in laterite layer and the brown clay layer at a depth of 5–11 m. Moreover, the biological accumulate coefficient (BAC) and the contrast coefficient (CM) were calculated to assess the sensitivity and concentrating ability of Populus canadensis and Cinnamomun camphora. To investigate the response of the two species to metal stress, the contents of chlorophyll, malondialdehyde (MDA), and activities of superoxide dismutase (SOD) and peroxidase (POD) were determined. The result showed that Populus canadensis and Cinnamomun camphora have a high tolerance to metal stress and that both of the two species can indicate the content of Au, As, Pb, and Co in topsoil.