Detoxification function of the Arabidopsis sulphotransferase AtSOT12 by sulphonation of xenobiotics

Abstract

Cytosolic sulphotransferases have been implicated in inactivation of endogenous steroid hormones and detoxification of xenobiotics in human and animals. Yet, the function of plant sulphotransferases in xenobiotic sulphonation and detoxification has not been reported. In this study, we show that the Arabidopsis sulphotransferase AtSOT12 could sulphonate the bacterial-produced toxin cycloheximide. Loss-of-function mutant sot12 exhibited hypersensitive phenotype to cycloheximide, and expression of AtSOT12 protein in yeast cells conferred resistance to this toxic compound. AtSOT12 exhibited broad specificity and could sulphonate a variety of xenobiotics including phenolic and polycyclic compounds. Enzyme kinetics analysis indicated that AtSOT12 has different selectivity for simple phenolics with different side chains, and the position of the side chain in the simple phenolic compounds affects substrate binding affinity and catalytic efficiency. We proposed that the broad specificity and induced production of AtSOT12 may have rendered this enzyme to not only modify endogenous molecules such as salicylic acid as we previously reported, but also sulphonate pathogen-produced toxic small molecules to protect them from infection. Sulphonation of small molecules in plants may constitute a rapid way to inactivate or change the physiochemical properties of biologically active molecules that could have profound effects on plant growth, development and defence.

The role of promoter cis-element, mRNA capping, and ROS in the repression and salt-inducible expression of AtSOT12 in Arabidopsis

“…Our previous research indicated that AtSOT12 gene is a multiple stress inducible gene and can be highly induced by NaCl treatment ( Baek et al, 2010 ; Chen et al, 2015 ). The approximately 1 kb sequence in front of the initiation codon (ATG) of the AtSOT12 gene including 208 bp 5′-UTR, 207 bp promoter region, and 624 bp upstream sequence ( Figure 1A ) was validated to be a salt inducible promoter that could drive salt inducible expression of the luciferase reporter gene in Arabidopsis ( Jiang et al, 2013 ).…”

“…It has been shown that sulfate availability influences ABA under salt stress ( Cao et al, 2014 ). Perhaps AtSOT12 is one of the key enzymes regulating sulfur pools in the guard cells due to its strong induction by salt stress and its wide substrates selectivity ( Baek et al, 2010 ; Chen et al, 2015 ). Through modulating sulfur contents, AtSOT12 may regulate ABA levels thus play a role in guard cell function.…”

“…Salt stress has been reported to increase sulfur contents and sulfur assimilation ( Rodríguez-Hernández et al, 2014 ; Nazar et al, 2015 ). Thus, it is conceivable that the pericycle cells are sites for sulfur accumulation, transport, and assimilation and AtSOT12 functions in these cells for sulfur assimilation by sulfonating a variety of small molecules ( Chen et al, 2015 ). Sulfur assimilation via AtSOT12 in the pericycle cells may be a molecular response contributing to salt stress tolerance.…”

“…The Arabidopsis sulfotransferase gene AtSOT12 is one of the salt inducible genes identified as NaCl specific in the transcriptome analysis by Kreps et al (2002) . However, our further study on the functions of AtSOT12 revealed that AtSOT12 gene is induced by multiple stress conditions including salt and osmotic stress ( Baek et al, 2010 ; Chen et al, 2015 ). This suggests that the induction of AtSOT12 expression by NaCl treatment may consist of both osmotic and ion stress components.…”

Improving analytical methods for protein-protein interaction through implementation of chemically inducible dimerization

“…We employed the proteins UGT74B1 and SOT16 from the Arabidopsis GLS pathway as bait and prey respectively. To evaluate specificity, we included the closely related SOT12, which functions in the synthesis of brassinosteroids 26 as well as detoxification of xenobiotics 27 . Co-transformation of FRB-NubG alone and the UGT74B1-containg bait construct did not give rise to activation of the reporter, demonstrating that this bait did not auto-activate the reporters under the applied conditions ( Fig.…”