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Title: BRUTUS and its paralogs, BTS LIKE1 and BTS LIKE2, encode important negative regulators of the iron deficiency response in Arabidopsis thaliana

Author
item HINDT, MARIA - Dartmouth College
item AKMAKJIAN, GARO - Dartmouth College
item PIVARSKI, KARA - Dartmouth College
item PUNSHON, TRACY - Dartmouth College
item Baxter, Ivan
item SALT, DAVID - University Of Aberdeen
item GUERINOT, MARY LOU - Dartmouth College

Submitted to: Metallomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2017
Publication Date: 6/16/2017
Publication URL: https://handle.nal.usda.gov/10113/5729158
Citation: Hindt, M.N., Akmakjian, G.Z., Pivarski, K.L., Punshon, T., Baxter, I.R., Salt, D., Guerinot, M. 2017. BRUTUS and its paralogs, BTS LIKE1 and BTS LIKE2, encode important negative regulators of the iron deficiency response in Arabidopsis thaliana. Metallomics. doi: 10.1039/c7mt00152e.

Interpretive Summary: Iron (Fe) is required for plant and human health, but it can also be toxic when present in excess. Therefore Fe levels must be tightly controlled. In the model plant Arabidopsis thaliana a gene named BRUTUS (BTS) is involved in keeping the Fe deficiency response turned off. In this paper, we show that two similar genes act redundantly in the same pathway. When both genes are disrupted, the plants have increased tolerance to Fe deficiency. We further generated a triple mutant with loss of both genes and a partial loss of BTS function that exhibits even greater tolerance to Fe-deficient conditions and increased Fe accumulation without any resulting Fe toxicity effects. Finally, we identified a mutant carrying a novel missense mutation of BTS that has the Fe deficiency response turned on in the root all the time, leading to Fe toxicity when plants are grown under Fe-sufficient conditions. However, this mutant does not exhibit any induction of the Fe deficiency response in the shoot and coating the leaves with Fe suggests that this mutant has a defect in shoot-to-root Fe signaling. Understanding this signaling pathway could be used to improve the performance of crops such as Soybean in iron deficient soils, which are a significant cause of reduced yield.

Technical Abstract: Iron (Fe) is required for plant health, but it can also be toxic when present in excess. Therefore, Fe levels must be tightly controlled. The Arabidopsis thaliana E3 ligase BRUTUS (BTS) is involved in the negative regulation of the Fe deficiency response and we show here that the two A. thaliana BTS paralogs, BTS LIKE1 (BTSL1) and BTS LIKE2 (BTSL2) encode proteins that act redundantly as negative regulators of the Fe deficiency response. Loss of both of these E3 ligases enhances tolerance to Fe deficiency. We further generated a triple mutant with loss of both BTS paralogs and a partial loss of BTS expression that exhibits even greater tolerance to Fe-deficient conditions and increased Fe accumulation without any resulting Fe toxicity effects. Finally, we identified a mutant carrying a novel missense mutation of BTS that exhibits an Fe deficiency response in the root when grown under both Fe-deficient and Fe-sufficient conditions, leading to Fe toxicity when plants are grown under Fe-sufficient conditions.