Dual transcriptomics of wild-type and Mtabcg36 nodules reveals differential response of symbiotic partners to metal stress in Medicago truncatula

Authors: CHAKRABORTY, SANHITA - Texas A&M University Institute For Advancing Health Through Agriculture; SHARMA, REENA - Brookhaven National Laboratory; BHAT, ADITI - Brookhaven National Laboratory; Curtin, Shaun; Paape, Timothy - Tim

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/3/2024
Publication Date: 6/3/2024
Citation: Chakraborty, S., Sharma, R., Bhat, A., Curtin, S.J., Paape, T.D. 2024. Dual transcriptomics of wild-type and Mtabcg36 nodules reveals differential response of symbiotic partners to metal stress in Medicago truncatula [abstract]. North American Symbiotic Nitrogen Fixation Conference (NASNFC). June 2-7, 2024; Burlington, VT. Poster presentation.

Interpretive Summary:

Technical Abstract: ATP-binding cassette (ABC) transporters are ubiquitous in all forms of life on earth. In plants, these proteins transport various substrates such as metal ions, hormones, lipid precursors, and pigment precursors, and are involved in ion homeostasis, immunity, and symbiosis. In Medicago truncatula, the disruption of MtABCG36 reduces nodule number. Because ion homeostasis is critical to nodule development, we studied the involvement of MtABCG36 in the plant’s response to the heavy metals cadmium (Cd) and zinc (Zn) in the nodules. Both Cd and Zn treatments decreased the number of nodules per gram of wild-type (WT) roots. To better understand the genome-wide response to metal stress in the nodules and the role of MtABCG36 in the response, we conducted dual transcriptomics of both symbiotic partners from nodules. We observed strong genotypic differences in responses in the transcriptome to the stress treatments in the plant. Also on the plant side, we discovered that over 70% of the differentially expressed genes (DEGs) in either treatment depends on the genotype and there is a strong overlap between the DEGs observed under Cd and Zn treatments. Moreover, several DEGs encoding ion transporters and symbiotic genes such DMI1, IPD3, VPY, NLP2, EFD1, Lb1, DNF2, nKCBP, and NAC969 were observed under both metal treatments in a genotype-dependent manner. Moreover, several auxin-associated genes were differentially regulated by the stress treatments in the WT and not in Mtabcg36, in line with the role of MtABCG36 in auxin homeostasis. The strongest effect on the bacterial transcriptome was observed between the WT and Mtabcg36 under Zn treatment. The DEGs in this category included those encoding several ABC-, and other transporters, and several nod, nif, and fix genes, indicating that symbiosis is negatively regulated by Zn in the bacterium in the absence of the host MtABCG36. Finally, using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), we discovered that Mtabcg36 nodules retain a higher quantity of Cd than the WT nodules under Cd, suggesting the possible role of MtABCG36 as a Cd exporter. Together, these findings highlight MtABCG36 as a key player in ion homeostasis in nodules.