Rhizospheric microbiomics integrated with plant transcriptomics provides insight into the Cd response mechanisms of the newly identified Cd accumulator Dahlia pinnata

Xiong Li; Boqun Li; Tao Jin; Huafang Chen; Gaojuan Zhao; Xiangshi Qin; Yongping Yang; Jianchu Xu

doi:10.3389/fpls.2022.1091056

Rhizospheric microbiomics integrated with plant transcriptomics provides insight into the Cd response mechanisms of the newly identified Cd accumulator Dahlia pinnata

Front Plant Sci. 2022 Dec 15:13:1091056. doi: 10.3389/fpls.2022.1091056. eCollection 2022.

Authors

Xiong Li^{1

2

3}, Boqun Li⁴, Tao Jin⁴, Huafang Chen^{1

2}, Gaojuan Zhao^{1

2}, Xiangshi Qin³, Yongping Yang^{3

5}, Jianchu Xu^{1

2}

Affiliations

¹ Department of Economic Plants and Biotechnology, Yunnan Key Laboratory for Wild Plant Resources, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
² Center for Mountain Futures, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
³ Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
⁴ Science and Technology Information Center, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China.
⁵ Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Xishuangbanna, China.

Abstract

Phytoremediation that depends on excellent plant resources and effective enhancing measures is important for remediating heavy metal-contaminated soils. This study investigated the cadmium (Cd) tolerance and accumulation characteristics of Dahlia pinnata Cav. to evaluate its Cd phytoremediation potential. Testing in soils spiked with 5-45 mg kg^-1 Cd showed that D. pinnata has a strong Cd tolerance capacity and appreciable shoot Cd bioconcentration factors (0.80-1.32) and translocation factors (0.81-1.59), indicating that D. pinnata can be defined as a Cd accumulator. In the rhizosphere, Cd stress (45 mg kg^-1 Cd) did not change the soil physicochemical properties but influenced the bacterial community composition compared to control conditions. Notably, the increased abundance of the bacterial phylum Patescibacteria and the dominance of several Cd-tolerant plant growth-promoting rhizobacteria (e.g., Sphingomonas, Gemmatimonas, Bryobacter, Flavisolibacter, Nocardioides, and Bradyrhizobium) likely facilitated Cd tolerance and accumulation in D. pinnata. Comparative transcriptomic analysis showed that Cd significantly induced (P < 0.001) the expression of genes involved in lignin synthesis in D. pinnata roots and leaves, which are likely to fix Cd²⁺ to the cell wall and inhibit Cd entry into the cytoplasm. Moreover, Cd induced a sophisticated signal transduction network that initiated detoxification processes in roots as well as ethylene synthesis from methionine metabolism to regulate Cd responses in leaves. This study suggests that D. pinnata can be potentially used for phytoextraction and improves our understanding of Cd-response mechanisms in plants from rhizospheric and molecular perspectives.

Keywords: Dahlia pinnata; heavy metal contamination; phytoextraction; rhizobacteria; signal transduction.