Priyanka Kushwaha

Mentor: 

Raina M Maier, PhD

Department: 

Environmental Science Department 

Abstract: 

Influence of compost amendment on the relationship between plant gene expression and microbial community diversity in remediation of acidic metalliferous mine tailings

Successful phytoremediation of acidic metal-contaminated mine tailings requires amendments to condition tailings properties prior to plant establishment. Previous research has demonstrated enhanced vegetation establishment, including Atriplex lentiformis, following compost amendment of metal-contaminated mine tailings. However, little is known about the plant genetic responses during remediation, or how these responses influences soil microbial diversity (and vice versa). The objective of this project is to identify relationships between tailings properties, the soil microbiome, and plant stress response genes during growth of Atriplex lentiformis in compost-amended (10%, 15%, 20% w/w) mine tailings. Analyses include RNA-Seq for plant root gene expression, 16S rRNA amplicon sequencing for bacterial/archaeal communities, metal concentrations in both tailings and plant organs, and phenotypic measures of plant stress. Plants from the intermediate treatment (15%; TC15) had the most visible stress response and Zn levels in leaves exceeded the hyperaccumulations values (3,000 mg kg^-1), an indication of different compost treatments altering plant metal uptake. Microbial analysis identified Alicyclobacillus, Hydrotalea, and Pseudolabrys taxa with the highest relative abundance in TC15, and these taxa were strongly associated with Zn accumulation.  Furthermore, we identified 190 root genes with significant gene expression changes. These root genes were associated with different pathways including, abscisic acid and auxin signaling, defense responses, ion channels, metal ion binding, oxidative stress, transcription regulation, and transmembrane transport. However, root gene expression changes were not directly related to increasing levels of compost. For instance, there were 15 genes that were up-regulated in TC15, whereas 106 genes were down-regulated in TC15. Collectively, the variables that were analyzed in the partial least square (PLS) regression model explained 86% of the variance in Zn accumulation in A. lentiformis leaves. The most important factors for Zn accumulation were Zn shoot concentrations, leaf stress symptoms, plant root genes, and microbial taxa. Therefore, our results suggest there are strong plant-microbiome associations that drive Zn accumulation in A. lentiformis and different plant gene pathways are involved in alleviating varying levels of metal stress. Future work is needed to gain a mechanistic understanding of these plant-microbiome interactions to optimize phytoremediation strategies as they will govern the success or failure of the revegetation process.