Figure 1.

Transient induction of the noncatalytic PDX1.2 by heat stress in Arabidopsis but not its catalytic counterparts. A, Schematic representation of the intronless PDX1 genes of Arabidopsis; the single exon in each case is depicted in black and fragments of the respective upstream and downstream regions in gray. The critical enzymatic residues [Asp-40 (D40), Lys-97 (K97), and Lys-165 (K165), AtPDX1.3 numbering] are indicated in the catalytic PDX1s (cPDX1; AtPDX1.1, AtPDX1.3), which are not conserved in the noncatalytic PDX1 of Arabidopsis (ncPDX1; AtPDX1.2). B and C, Quantitative analysis of AtPDX1.2 and AtHSP101 expression, respectively, as a function of temperature. The fold-change is depicted relative to that at 22°C (set to 1). Seedlings were incubated for 1 h at the indicated temperatures. D, Relative fold-change of AtPDX1.1 (black) and AtPDX1.3 (gray) expression as in (B) and (C). E and F, Relative fold-change of AtPDX1.2 and AtHSP101 expression, respectively, before heat stress (NS; 22°C) and after heat stress (HS; 37°C for 1 h) and after the indicated recovery periods at 22°C. The fold-change is depicted relative to NS (set to 1). G, Relative fold-change of AtPDX1.1 (black) and AtPDX1.3 (gray) expression as in (E) and (F). In each case, 8-d-old Arabidopsis seedlings precultivated at 22°C under a 16-h photoperiod (120 μmol photons m⁻² s⁻¹) and 8 h of darkness at 18°C were used. Statistical significance was calculated from a pairwise comparison to that at 22°C as indicated by an asterisk for P < 0.001. In all cases, error bars represent se.