ATP-sulfurylase, sulfur-compounds, and plant stress tolerance

Abstract

Sulfur (S) stands fourth in the list of major plant nutrients after N, P, and K. Sulfate (SO4 (2-)), a form of soil-S taken up by plant roots is metabolically inert. As the first committed step of S-assimilation, ATP-sulfurylase (ATP-S) catalyzes SO4 (2-)-activation and yields activated high-energy compound adenosine-5(')-phosphosulfate that is reduced to sulfide (S(2-)) and incorporated into cysteine (Cys). In turn, Cys acts as a precursor or donor of reduced S for a range of S-compounds such as methionine (Met), glutathione (GSH), homo-GSH (h-GSH), and phytochelatins (PCs). Among S-compounds, GSH, h-GSH, and PCs are known for their involvement in plant tolerance to varied abiotic stresses, Cys is a major component of GSH, h-GSH, and PCs; whereas, several key stress-metabolites such as ethylene, are controlled by Met through its first metabolite S-adenosylmethionine. With the major aim of briefly highlighting S-compound-mediated role of ATP-S in plant stress tolerance, this paper: (a) overviews ATP-S structure/chemistry and occurrence, (b) appraises recent literature available on ATP-S roles and regulations, and underlying mechanisms in plant abiotic and biotic stress tolerance, (c) summarizes ATP-S-intrinsic regulation by major S-compounds, and (d) highlights major open-questions in the present context. Future research in the current direction can be devised based on the discussion outcomes.

Keywords: ATP-sulfurylase; organic S-compounds; stress tolerance; sulfur assimilation.

FIGURE 1

Schematic representation of pathway of sulfate assimilation, reaction catalyzed by ATP-sulfurylase (ATP-S), and its regulation by major factors. Role of ATP-S in plant stress tolerance through sulfur/cysteine rich and sulfated compounds is outlined. Positive and negative regulation of ATP-S is indicated by arrows and blunt ends, respectively, [¹Kawashima et al. (2011); ²Yatusevich et al. (2010); ³Hopkins et al. (2004); ⁴Schiavon et al. (2007); ⁵van de Mortel et al. (2008); ⁶Guo et al. (2009); ⁷Gill et al. (2012); ⁸Bashir et al. (2013); ⁹Asgher et al. (2014); ¹⁰Leao et al. (2014); ¹¹Phartiyal et al. (2006); ¹²Ruiz and Blumwald (2002); ¹³Nazar et al. (2011); ¹⁴Passera et al. (1989); ¹⁵Huseby et al. (2013); ¹⁶Rotte and Leustek (2000); ¹⁷Takahashi et al. (1997); ¹⁸Liang et al. (2010); ¹⁹Lappartient and Touraine (1997); ²⁰Lappartient and Touraine (1996); ²¹Vauclare et al. (2002)]. (APS, adenosine 5^′-phosphosulfate; Cys, cysteine; AsA, ascorbate; GSH, reduced glutathione; PCs, phytochelatins; MTs, metallothioneins; ROS, reactive oxygen species).