Mechanisms involved in the sequestration and resistance of cadmium for a plant-associated Pseudomonas strain.

Understanding Cd-resistant bacterial cadmium (Cd) resistance systems is crucial for improving microremediation in Cd-contaminated environments. However, these mechanisms are not fully understood in plant-associated bacteria. In the present study, we investigated the mechanisms underlying Cd sequestration and resistance in the strain AN-B15. These results showed that extracellular Cd sequestration by complexation in strain AN-B15 was primarily responsible for the removal of Cd from the solution. Transcriptome analyses have shown that the mechanisms of Cd resistance at the transcriptional level involve collaborative processes involving multiple metabolic pathways. The AN-B15 strain upregulated the expression of genes related to exopolymeric substance synthesis, metal transport, Fe-S cluster biogenesis, iron recruitment, reactive oxygen species oxidative stress defense, and DNA and protein repair to resist Cd-induced stress. Furthermore, inoculation with AN-B15 alleviated Cd-induced toxicity and reduced Cd uptake in the shoots of wheat seedlings, indicating its potential for remediation. Overall, the results improve our understanding of the mechanisms involved in Cd resistance in bacteria and thus have important implications for improving microremediation.

Genome-Wide Analysis of the ATP-Binding Cassette (ABC) Transporter Family in Zea mays L. and Its Response to Heavy Metal Stresses.

The ATP-binding cassette (ABC) transporter family is one of the largest eukaryotic protein families. Its members play roles in numerous metabolic processes in plants by releasing energy for substrate transport across membranes through hydrolysis of ATP. Maize belongs to the monocotyledonous plant family, Gramineae, and is one of the most important food crops in the world. We constructed a phylogenetic tree with individual ABC genes from maize, rice, sorghum, Arabidopsis, and poplar. This revealed eight families, each containing ABC genes from both monocotyledonous and dicotyledonous plants, indicating that the amplification events of ABC gene families predate the divergence of plant monocotyledons. To further understand the functions of ABC genes in maize growth and development, we analyzed the expression patterns of maize ABC family genes in eight tissues and organs based on the transcriptome database on the Genevestigator website. We identified 133 ABC genes expressed in most of the eight tissues and organs examined, especially during root and leaf development. Furthermore, transcriptome analysis of ZmABC genes showed that exposure to metallic lead induced differential expression of many maize ABC genes, mainly including ZmABC 012, 013, 015, 031, 040, 043, 065, 078, 080, 085, 088, 102, 107, 111, 130 and 131 genes, etc. These results indicated that ZmABC genes play an important role in the response to heavy metal stress. The comprehensive analysis of this study provides a foundation for further studies into the roles of ABC genes in maize.

Tillage activates iron to prevent soil organic carbon loss following forest conversion to cornfields in tropical acidic red soils.

Previous studies have shown that deforestation and planting of corn resulted in the loss of soil organic carbon (SOC). However, this is not inevitable in regions with acidic red soil. We selected six cornfields that have been planted for 34 years and adjacent forest plots in southwest China. Using a structural equation model, we identified the SOC contents and 42 soil environmental factors in 11 soil layers that are conducive to SOC storage, and evaluated their relative weights hierarchically (0-40, 40-100, and 100-140 cm). Our results surprisingly indicated that after forest had been converted into cornfield, the SOC density did not change in any layer. In acidic red soil, reactive iron (Feo), soil water content, nitrogen, and pH were the main soil environmental factors that affected the storage of SOC. In the 0-40 cm soil layer, compared to forests, the contribution of Feo in cornfields increased significantly (by 11.65%), due to farming promoting the activation of iron, while the contribution of nitrogen decreased significantly (by 9.65%). In the 100-140 cm soil layer, the contribution of soil environmental factors was similar to that in the forest system, but the pH in cornfields increasing significantly (by 21.5%) may result from the leaching of hydrogen ions. Although the cultivation of cornfields caused a loss of nitrogen in the 0-40 cm soil layer, the increase in Feo promoted combination of iron and soil organic carbon, avoiding the soil layer from SOC loss.

Cadmium pollution alters earthworm activity and thus leaf-litter decomposition and soil properties.

It has been reported that heavy metal contamination can affect litter decomposition and soil properties through its impact on microbial communities. However, it is still unclear whether the expected changes in earthworm activities in responses to heavy metal contamination could affect these properties. Therefore, we quantified earthworm (Eisenia fetida) responses in survival rate to lethal cadmium (Cd) concentrations (0, 50, 100, 150, 200, 250, and 300 mg L-1), and in burrowing ability, physiological characteristics, and feeding rate (on poplar leaf litter) to sub-lethal Cd concentrations (0, 15, 30, and 45 mg kg-1). Finally, sub-lethal influences of Cd on the decomposition rate of poplar leaf litter and on soil properties were investigated in the present of E. fetida. The 12-, 24-, 36-, and 48-h LC50 of Cd for E. fetida were 276.0, 208.6, 192.6, 179.8 mg L-1, respectively. With increasing Cd concentration, malondialdehyde was stimulated, superoxide dismutase first increased and then decreased, while feeding rate, total borrowing length, and maximum burrowing depth consistently decreased. Consequently, leaf-litter decomposition rate and soil nutrient concentrations generally decreased with increasing Cd concentration. Our results indicate that, by affecting earthworm activities, Cd inhibited leaf-litter decomposition and led to the degradation of soil fertility. This study highlights the importance of earthworms in mediating soil functions under heavy metal stress.

[Epidemiological investigation on congenital heart disease in several regions of Yunnan province].

OBJECTIVE: To investigate the distribution of congenital heart disease (CHD) aged 3 - 18 in several regions of Yunnan province. METHODS: Cross-rectional studies were carried out among 48 638 children from Xishuangbanna, Dali, Baoshan Longling, Luxi Mangshi and Gejiu in Yunnan province with stratified, clustered sampling. RESULTS: The overall morbidity of CHD was 5.08 per thousand with 5.09 per thousand in males and 5.07 per thousand in females. Morbidity rates in different regions were 2.75 per thousand in Xishuangbanna, 7.85 per thousand in Dali, 9.59 per thousand in Baoshan Long ling, 4.80 per thousand in Gejiu, 16.99 per thousand in Luxi Wuchalu. However, in the same area, rates were different among different residents:3.25 per thousand in Gejiu, and was 9.10 per thousand in Laochang stannum mine, 11.20 per thousand in Datunxuanchang; 5.74 per thousand at the city of Baoshan Longling, 11.35 per thousand at countryside; 4.90 per thousand at the city of Dali, 8.71 per thousand at countryside; 1.69 per thousand at the city of Xishuangbanna, 4.40 per thousand at country. Morbidity rates in different ethnic groups were as follows: 5.39 per thousand in Dai, 6.83 per thousand in Jinuo, 0 per thousand in Hani, 8.12 per thousand in Bai, 14.18 per thousand in Jingpo. CONCLUSION: There were significant regional and ethnic differences seen in Yunnan on the mobidity of CHD which was different from the domestic literature reported.