Influence of chilling stress on the intercellular distribution of assimilatory sulfate reduction and thiols in Zea mays

The effect of chilling on the intercellular distribution of mRNAs for enzym es of assimilatory sulfate reduction, the activity of adenosine 5'-phosphos ulfate reductase (APR), and the level of glutathione was analysed in leaves and roots of maize (Zea mays L). At 25 degreesC the mRNAs for APR, ATP sul furylase, and sulfite reductase accumulated in bundle-sheath only, whereas the mRNA for O-acetylserine sulfhydrylase was also detected in mesophyll ce lls. Glutathione was predominantly detected in mesophyll cells; however, ox idized glutathione was equally distributed between the two cell types. Chil ling at 12 degreesC induced oxidative stress which resulted in increased co ncentrations of oxidized glutathione in both cell types and a prominent inc rease of APR mRNA and activity in bundle-sheath cells. After chilling, mRNA s for APR and sulfite reductase, as well as low APR activity, were detected in mesophyll cells. In roots, APR mRNA and activity were at higher levers in root tips than in the mature root and were greatly increased after chill ing. These results demonstrate that chilling stress affected the levers and the intercellular distribution of mRNAs for enzymes of sulfate assimilatio n.