Demand-Driven Control of Root ATP Sulfurylase Activity and SO42- Uptake in Intact Canola (The Role of Phloem-Translocated Glutathione)

Abstract

The activity of ATP sulfurylase extracted from roots of intact canola (Brassica napus 1. cv Drakkar) increased after withdrawal of the S source from the nutrient solution and declined after refeeding S0,'-to S-starved plants. The rate of S0,'-uptake by the roots was similarly influenced. ldentical responses were obtained in SO,'--fed roots when one-half of the root system was starved for S. S is predominantly available to higher plants as S0,'-taken up from soil by the roots. The rate of S uptake by plant roots, especially those of crop species, which have been bred for their fast growth capacity and high harvest potential, is controlled by regulatory processes that operate in such a way that the needs of the whole organism are matched by rates of S uptake. A good illustration of this behavior is provided by the severalfold enhancement of S0: -uptake observed in plants previously deprived of S for periods of a few hours to a few days (

Sulphate uptake and xylem loading of mycorrhizal beech roots

“…Since sulphur starvation stimulate sulphate uptake (Lass & Ullrich-Eberius, 1984 ;Clarkson & Saker, 1989 ;Hawkesford & Belcher, 1991 ;Hawkesford, Davidian & Grignon, 1993 ;Lee, 1993) and high sulphur supply leads to reduced uptake rates of sulphate (Kreuzwieser, Herschbach & Rennenberg, 1996), it appears that sulphate transport processes are well regulated. Consistent with this view Lappartient & Touraine (1996) recently proposed a demand-driven control of sulphate uptake in Canola plants.…”

“…Sulphur depletion led to increased sulphate uptake and xylem loading, whereas both processes were diminished in response to a surplus of sulphate. Many studies with herbaceous plants also reported higher rates of sulphate uptake and xylem loading when the plants were starved of sulphur (Clarkson & Saker, 1989 ;Herschbach & Rennenberg, 1991 ;Lappartient & Touraine, 1996). Lappartient & Touraine (1996) interpreted these findings as a response of plants to maintain homoeostasis of sulphur in its cells.…”

“…The effectors proposed for such a regulation of sulphate uptake include sulphate (Jensen & Ko$ nig, 1982 ;Cram 1983 a, b) as well as products of assimilatory sulphate reduction like -cysteine, -methionine or the tripeptide glutathione (Rennenberg et al, 1988 ;Herschbach & Rennenberg, 1991Kreuzwieser et al, 1996 ;Lappartient & Touraine, 1996). Rennenberg (1995) and Lappartient & Touraine (1996) hypothesized that glutathione is the signal mediating demand-driven control of sulphate uptake. This product of assimilatory sulphate reduction could act as a long distance message that is phloem-transported to the roots, where it signals the shoot's sulphur status (Rennenberg, 1995).…”

Exogenous salicylic acid improves photosynthesis and growth through increase in ascorbate-glutathione metabolism and S assimilation in mustard under salt stress

“…34 It has been reported that withdrawal of S from the medium leads to decreased levels of sulfate and GSH in Arabidopsis and canola plants tissues resulting in the induction of sulfate transporter systems and ATPS activity. 35,36 The inhibition in the activity of ATPS1 and APR results in the inhibition of GSH synthesis. 37,38,39 Supplementation of 0.5 mM SA results in the substantial increase in ATP sulfurylase, serine acetyl transferase activity and Cys content under salt stress and helps in reversing the effects of NaCl ¡ induced ROS on photosynthesis.…”

“…Activity of ATP-sulfurylase (ATPS) was measured in leaves by the method of Lappartient and Touraine 35 . Fresh leaf tissues (1 gm) was ground at 4 C in a buffer consisting of 10 mM Na 2 EDTA, 20 mM Tris-HCl (pH 8.0), 2 mM dithiothreitol (DTT), and 0.01 g mL ¡1 PVP, using 1:4 (w/v) tissue to buffer ratio.…”