Figure 4.

Proline accumulation and expression of proline metabolism genes in wild-type (WT) and esk1 Arabidopsis. (A) Proline levels in nonacclimated plants (open bars), in plants cold acclimated at 4°C for 2 days (shaded bars), and in plants 10 hr after application of 100 mM proline (solid bars). Harvested leaf tissue was frozen in liquid nitrogen and lyophilized. Free amino acids were extracted and quantified by using an amino acid analyzer. (B) Gel-blot analysis of transcript levels for genes encoding Δ¹-pyrroline-5-carboxylate synthetase (P5CS) and proline oxidase (AtPOX). Methods are those described in Fig. 3.