Sulfate Assimilation in C₄ Plants

Abstract

The activity of ATP sulfurylase, cysteine synthase, and cystathionine jl-lyase was measured in crude leaf extracts, bundle sheath strands, and mesophyll and bundle sheath chloroplasts to determine the location of sulfate assimilation of C4 plant leaves. Almost all the ATP sulfurylase activity was located in the bundle sheath chloroplasts while cysteine synthase and cystathionine j-lyase activity was located, in different proportions, in both chloroplast types.A new spectrophotometric assay for measuring ATP sulfurylase activity is also described.The C4 pathway of CO2 assimilation is compartmentalized into specific cell types with atmospheric CO2 initially being fixed into organic acids in the Although it is generally agreed that in C3 plants, chloroplasts are the main site of S42-assimilation (activation and reduction to S2-) (1) the subcellular distribution of cysteine synthase (EC 4.2.99.8) appears to differ between plant species. In wheat and rape leaves and kidney bean seedlings, the enzyme is apparently cytoplasmic (3,14,16) whereas in spinach, white clover, and pea leaves the enzyme is associated with chloroplasts (7, 15). A recent report suggests that cystathionine ,-lyase (EC 4.4.1.8) in barley leaves is at least partially chloroplastic (17). This paper reports on the inter-and intracellular location of ATP sulfurylase, cysteine synthase and cystathionine ,B-lyase in Zea mays. A new spectrophotometric assay for ATP sulfurylase is also described.

Sulfate assimilation and glutathione synthesis in C4 plants

“…Several groups reported that 75-100% of total leaf ATP sulfurylase activity in maize was confined to BSC (Gerwick Passera and Ghisi 1982;Schmutz and Brunold 1984;Burnell 1984). These findings were extended to 17 other C 4 species of all three C 4 subtypes, where 95-100% of total leaf ATPS activity was localised in chloroplasts of BSC (Gerwick et al 1980).…”

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

“…This reaction is activated by ATP sulfurylase (Osslung et al, 1982;Renosto et al, 1993;Klonus et al, 1994;Leustek et al, 1994). Most SO2-reduction, as well as APS formation, occurs in mesophyll cells in leaves, where the major part of activity is associated with chloroplasts (Burnell, 1984;Lunn et al, 1990;Renosto et al, 1993). Cacco et al (1977) reported that the activity of ATP sulfurylase in roots was subjected to variations, fitting the same pattern as the S02-uptake rate, suggesting that ATP sulfurylase activity and SOZ-uptake may be regulated in a similar way.…”

Reconstruction of Metabolic Pathways, Protein Expression, and Homeostasis Machineries across Maize Bundle Sheath and Mesophyll Chloroplasts: Large-Scale Quantitative Proteomics Using the First Maize Genome Assembly

“…11). Older studies using other assays than proteomics revealed that the activities of ATP sulfurylase (ATPS) and adenosine 5#-phosphosulfate sulfotransferase (APR) in maize were confined to BS cells, while Cys synthase (O-acetyl-Ser thiol lyase [OASTL]) activity is found in both cell types but at a higher level in M cells (Gerwick and Black, 1979;Burnell, 1984;Schmutz and Brunold, 1984;Burgener et al, 1998). These previous observations are consistent with our current observations for ATPS2 and APR3 and -4, which showed BS-M ratios of 3.86, 9.92, and 19.75, respectively, whereas two OASTL isoforms (also named Cys synthase) were 40% to 100% higher in M chloroplasts than in BS chloroplasts.…”