Differential expression of two P5CS genes controlling proline accumulation during salt‐stress requires ABA and is regulated by ABA1, ABI1 and AXR2 in Arabidopsis

Abstract

Summary Proline is a common compatible osmolyte in higher plants. Proline accumulation in response to water stress and salinity is preceded by a rapid increase of the mRNA level of Δ1‐pyrroline‐5‐carboxylate synthase (P5CS) controlling the rate‐limiting step of glutamate‐derived proline biosynthesis. P5CS is encoded by two differentially regulated genes in Arabidopsis. Gene AtP5CS1 mapped to chromosome 2‐78.5 is expressed in most plant organs, but silent in dividing cells. Gene AtP5CS2 located close to marker m457 on chromosome 3–101.3 contributes 20–40% of total P5CS mRNA in plant tissues, but is solely responsible for the synthesis of abundant P5CS mRNA in rapidly dividing cell cultures. Accumulation of AtP5CS transcripts is regulated in a tissue specific manner and inducible by drought, salinity, ABA, and to a lesser extent by auxin. Induction of AtP5CS1 mRNA accumulation in salt‐treated seedlings involves an immediate early transcriptional response regulated by ABA signalling that is not inhibited by cycloheximide, but abolished by the deficiency of ABA biosynthesis in the aba1 Arabidopsis mutant. However, inhibition of protein synthesis by cycloheximide prevents the induction of AtP5CS2 mRNA accumulation, and blocks further increase of AtP5CS1 mRNA levels during the second, slow phase of salt‐induction. Mutations abi1 and axr2, affecting ABA‐perception in Arabidopsis, reduce the accumulation of both AtP5CS mRNAs during salt‐stress, whereas ABA‐signalling functions defined by the abi2 and abi3 mutations have no effect on salt‐induction of the AtP5CS genes.

A STRESS-RESPONSIVE NAC1-Regulated Protein Phosphatase Gene RiceProtein Phosphatase18Modulates Drought and Oxidative Stress Tolerance through Abscisic Acid-Independent Reactive Oxygen Species Scavenging in Rice

“…Some plant PP2Cs have been characterized with regulatory roles in stress tolerance. ABI1 and PP2CA are two important PP2Cs for plant tolerance to several abiotic stresses, including salt, drought, and freezing, by regulation of ABA signaling (Strizhov et al, 1997;Gosti et al, 1999;Tähtiharju and Palva, 2001). OE of an ABI1 ortholog in the liverwort Marchantia polymorpha resulted in reduced freezing and osmotic stress tolerance (Tougane et al, 2010).…”

“…In Arabidopsis, group A PP2Cs, including ABSCISIC ACID INSENSITIVE1 (ABI1), are well characterized and described as negative regulators of abscisic acid (ABA) signaling pathways involved in diverse processes, including seed germination, stomatal movement, and stress responses (Leung et al, 1997;Saez et al, 2004;Kuhn et al, 2006;Zhang et al, 2012). ABI1 and PP2CA are also essential for plant tolerance to several abiotic stresses, including salt, drought, and freezing (Strizhov et al, 1997;Gosti et al, 1999;Tähtiharju and Palva, 2001). The group B member ARABIDOPSIS SER/ THR PHOSPHATASE OF TYPE 2C 1 (AP2C1) inactivates the mitogen-activated protein kinases (MAPKs) MPK4 and MPK6 involved in regulating stress hormone levels and defense responses (Schweighofer et al, 2007).…”

Enhancement of Abscisic Acid Sensitivity and Reduction of Water Consumption in Arabidopsis by Combined Inactivation of the Protein Phosphatases Type 2C ABI1 and HAB1

“…To this end, we used qRT-PCR to analyze the expression of the ABA-and drought-responsive RAB18, P5CS1, RD29B, KIN1, RD29A, and RD22 genes, in wild type, single, and double mutants. These gene markers have been widely used to monitor the ABA and stress response pathways in plants (Kurkela and Franck, 1990;Lang and Palva, 1992;Yamaguchi-Shinozaki and Shinozaki, 1994;Strizhov et al, 1997;Abe et al, 2003). In general, in the absence of ABA or stress treatments, these gene markers show a low expression, which is strongly upregulated in response to the inductive signal.…”

Isolation of the Ornithine-δ-Aminotransferase cDNA and Effect of Salt Stress on Its Expression inArabidopsis thaliana1

“…Regulation of the glutamate route is relatively well documented: moth bean (Vigna aconitifolia) P5CS enzyme synthesized in Escherichia coli is allosterically inhibited by Pro (Hu et al, 1992). The stimulation of Pro biosynthesis under salt and water stress is also correlated with an increase in the levels of P5CR and P5CS mRNA (Hu et al, 1992;Verbruggen et al, 1993;Savoure et al, 1995;Yoshiba et al, 1995;Strizhof et al, 1997).…”

“…Aiming to understand the role of ␦-OAT in the Pro biosynthesis, our approach was to study ␦-OAT in Arabidopsis thaliana, for which the enzymes of the glutamate pathway have already been cloned (Verbruggen et al, 1993;Yoshiba et al, 1995;Strizhof et al, 1997) and to determine how ␦-OAT expression varies as a function of plant development after salt stress.…”