Figure 7.

Incorporation Rates of Sulfate in Wild-Type and sir1-1 Plants.

(A) to (C) Leaf pieces of 7-week-old wild-type (black circles) and sir1-1 (white circles) plants, which were grown hydroponically under short-day conditions, were incubated with ³⁵SO₄^2--spiked half-strength Hoagland solution for 15 min (pulse, beginning at time 0) and subsequently kept in the same medium without radiolabel for 30 min (chase). Cys (A), GSH (B), and proteins (C) were extracted and separated by HPLC or specific precipitation. The incorporated ³⁵S label was quantified by scintillation counting.

(D) Total sum of incorporated ³⁵S label in Cys, GSH and proteins. The mean ± se from four independent extractions of the wild type and sir1-1 are shown. Asterisks indicate statistically significant (P < 0.05) differences from wild-type values.