Molecular Mechanisms of Polyisoprenoid Biosynthesis in Arabidopsis thaliana
SnRK2-Mediated Phosphorylation of cis-Prenyltransferases Regulates Polyisoprenoid Biosynthesis in Arabidopsis

Molecular mechanisms of polyisoprenoid biosynthesis in Arabidopsis thaliana.
Polyisoprenoids are linear polymers present in the cells of all living organisms. These compounds participate in numerous essential cellular processes, including protein glycosylation, protein prenylation, modulation of membrane permeability and fluidity, and responses to stress conditions. In eukaryotic cells, polyisoprenoids are accumulated as mixtures of homologues, and their composition and size of polyisoprenoid molecules, are variable and depend on the species of origin. Polyisoprenoid formation is catalyzed by dedicated enzymes, cis-prenyltransferases (CPTs), which are responsible for elongating the prenyl chain and regulating its length. Consequently, the composition of the polyisoprenoid mixtures correlates with a number of cis-prenyltransferases involved in their biosynthesis, e.g., only one CPT is found in animal cells, two in baker’s yeast, and several in plants.
So far, we have characterized 5 out of 9 potential CPTs from Arabidopsis thaliana and identified their end products. However, neither the biological significance of the complexity of this pathway nor the cellular roles of individual polyisoprenoid compounds have been fully elucidated. Despite their highly conserved primary structure, AtCPTs differ in their subcellular localization as well as in the length and profile of the synthesized polyprenyl chains. One of these enzymes exclusively produces a very short polyprenol containing seven isoprene units (i.u.), whereas the remaining AtCPTs generate mixtures of polyprenols ranging from mediumlength species to extremely long species. Arabidopsis possesses two types of CPTs: homodimeric enzymes, which act autonomously and heterodimeric enzymes, which require dimerization with a CPT-binding protein (Lew1) to acquire enzymatic activity. Moreover, some polyprenols formed by AtCPTs are converted into dolichols, while the others are not.
Our most recent studies focus on the genetic and cellular effects of a deficiency in the flower-specific CPT heterodimeric complex, CPT4-Lew1, on Arabidopsis pollen development and fertility. We also propose that, in addition to Lew1, other partner proteins may contribute to the regulation of CPT activity in Arabidopsis.
SnRK2-Mediated Phosphorylation of cis-Prenyltransferases Regulates Polyisoprenoid Biosynthesis in Arabidopsis
Our research investigates the post-translational regulation of cis-prenyltransferases (CPTs), enzymes that play a key role in the biosynthesis of polyisoprenoids. These compounds are essential cofactors of protein glycosylation across all domains of life and have recently been found to be involved in plant responses to environmental stress. In Arabidopsis thaliana, the plastid-localized CPT7 is responsible for synthesizing polyprenols (Pren-9 to Pren-11), which are integral components of thylakoid membranes that modulate their physical properties and impact photosynthetic performance. We observed that exposure to elevated temperatures (38°C) triggers a significant upregulation of CPT7 transcription and a corresponding accumulation of polyprenols, an adaptive response critical for plant survival at high temperatures. Concurrently, heat exposure strongly induces the expression of the SnRK2.3 kinase. Our previous findings indicate that CPT7 is phosphorylated by SnRK2 kinases, as shown by in vitro kinase assays and mass spectrometry analysis of the native CPT7p. Compared to wild-type plants, snrk2 mutant lines show reduced CPT7 expression, accompanied by a significant increase in polyprenol levels. These findings suggest that impaired phosphorylation enhances CPT7 enzymatic activity, thereby promoting polyprenol synthesis, while simultaneously suppressing CPT7 gene expression through a negative feedback mechanism. We therefore propose a model where SnRK2-mediated phosphorylation serves as an inhibitory switch for CPT7 activity. To our knowledge, this is the first evidence that the enzymatic function of a CPT is directly regulated by phosphorylation, highlighting a novel mechanism that links kinase signaling with polyprenol production and thermotolerance in plants.

講者: Dr. Liliana Surmacz (Associate Professor at the Laboratory of Lipid Biochemistry, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Poland)
Zuzanna Bechler (PhD Candidate, at the Laboratory of Lipid Biochemistry, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Poland)

主持人: Dr. Yee-yung Charng

時間:2025/10/21 10:30 AM

地點:農業科技大樓1樓A134演講廳