PLEIOTROPIC REGULATORY LOCUS 1 (PRL1) Integrates the Regulation of Sugar Responses with Isoprenoid Metabolism in Arabidopsis

Abstract

The biosynthesis of isoprenoids in plant cells occurs from precursors produced in the cytosol by the mevalonate (MVA) pathway and in the plastid by the methylerythritol 4-phosphate (MEP) pathway, but little is known about the mechanisms coordinating both pathways. Evidence of the importance of sugar signaling for such coordination in Arabidopsis thaliana is provided here by the characterization of a mutant showing an increased accumulation of MEP-derived isoprenoid products (chlorophylls and carotenoids) without changes in the levels of relevant MEP pathway transcripts, proteins, or enzyme activities. This mutant was found to be a new loss-of-function allele of PRL1 (Pleiotropic Regulatory Locus 1), a gene encoding a conserved WD-protein that functions as a global regulator of sugar, stress, and hormone responses, in part by inhibition of SNF1-related protein kinases (SnRK1). Consistent with the reported role of SnRK1 kinases in the phosphorylation and inactivation of the main regulatory enzyme of the MVA pathway (hydroxymethylglutaryl coenzyme-A reductase), its activity but not transcript or protein levels was reduced in prl1 seedlings. However, the accumulation of MVA-derived end products (sterols) was unaltered in mutant seedlings. Sucrose supplementation to wild-type seedlings phenocopied the prl1 mutation in terms of isoprenoid metabolism, suggesting that the observed isoprenoid phenotypes result from the increased sugar accumulation in the prl1 mutant. In summary, PRL1 appears to coordinate isoprenoid metabolism with sugar, hormone, and stress responses.

The Arabidopsis Mitochondria-Localized Pentatricopeptide Repeat Protein PGN Functions in Defense against Necrotrophic Fungi and Abiotic Stress Tolerance

“…Interestingly, expression of PRL1 is significantly repressed in the pgn mutant, suggesting that these two may have functional interaction in RNA metabolism in response to different abiotic and biotic stresses. In addition, prl1 plants are resistant to the methylerythritol phosphate pathway inhibitor clomazone, a phenotype observed with loss of function of LOI1, which encodes a mitochondrial PPRP (Kobayashi et al, 2007;Flores-Pérez et al, 2010).…”

Biosynthesis and biotechnological production of ginsenosides

“…Since PP2A is involved in abscisic acid and auxin signaling and PRL1 functions as a regulator of sugar, stress, and hormone response, it is possible that the HMGR activity is regulated by phytohormone and stress response. Furthermore, both MVA and MEP pathways have been shown to be coordinated by sugar and hormone molecules via the global regulator PRL1 (Flores-Perez et al, 2010).…”

TheSUD1Gene Encodes a Putative E3 Ubiquitin Ligase and Is a Positive Regulator of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Activity inArabidopsis

“…Whereas transcriptional modulation of HMGR has been demonstrated in many plant systems, evidence for mechanisms regulating HMGR activity at the posttranslational level is scarce. Thus, Nieto et al (2009) have shown that metabolic perturbations by enhancing or depleting the flux through the sterol pathway in Arabidopsis causes a compensatory response in HMGR activity, without changes in transcript or protein levels, and Flores-Pérez et al (2010) reported that the inactivation of the Arabidopsis WD protein PRL1 leads to reduced HMGR activity with no changes in transcript and protein levels. This effect could be related to the ability of PRL1 to interact and inhibit the activity of the Arabidopsis SNF1-related protein kinases (SnRK1) AKIN10 and AKIN11 (Bhalerao et al, 1999), presumably targeting them for ubiquitination and proteasomal degradation (Lee et al, 2008).…”