miR-27a augmentation via tail-vein injection of miR-27a mimic in high cholesterol diet-fed Apoe -/- mice shows down-regulation of hepatic Hmgcr and plasma cholesterol levels. Pathway and gene expression analyses show that miR-27a also targets several other genes (apart from Hmgcr) in cholesterol biosynthesis pathway. Taken together, miR-27a emerges as a key regulator of cholesterol biosynthesis and has therapeutic potential for clinical management of hypercholesterolemia. Copyright © 2020 American Society for Microbiology.Stress granules (SGs) are cytoplasmic aggregates formed upon stress when untranslated messenger ribonucleoproteins accumulate in the cells. In a GFP-library screening of the fission yeast SG proteins, Puf2 of the PUF family of RNA-binding proteins was identified that is required for SG formation after deprivation of glucose. Accordingly, puf2 mutant is defective in recovery from glucose starvation with a much longer lag to re-enter the cell cycle. In keeping with these results, Puf2 contains several low-complexity and intrinsically disordered protein regions with a tendency to form aggregates and, when over-expressed, represses translation to induce aggregation of poly(A) binding protein Pabp, the signature constituent of SGs. Intriguingly, over-expression of Puf2 also enhances the structure of processing bodies (PBs), another type of cytoplasmic RNA granules, a complex of factors involved in mRNA degradation. We demonstrate, in this study, a function of the fission yeast PB in SG formation and Puf2 may provide the link of these two structures. Copyright © 2020 American Society for Microbiology.The chloroplast glutamyl-tRNA (tRNAGlu) is unique in that it has two entirely different functions. In addition to acting in translation, it serves as substrate of glutamyl-tRNA reductase, the enzyme catalyzing the committed step in the tetrapyrrole biosynthetic pathway. How the tRNAGlu pool is distributed between the two pathways and whether tRNAGlu allocation limits tetrapyrrole biosynthesis and/or protein biosynthesis remains poorly understood. We have generated a series of transplastomic tobacco (Nicotiana tabacum) plants to alter tRNAGlu expression levels and also introduced a point mutation into the plastid trnE gene, which was reported to uncouple protein biosynthesis from tetrapyrrole biosynthesis in chloroplasts of the protist Euglena gracilis. We show that, rather than comparable uncoupling of the two pathways, the trnE mutation is lethal in tobacco as it inhibits tRNA processing, thus preventing translation of glutamate codons. Ectopic expression of the mutated trnE gene uncovered an unexpected inhibition of glutamyl-tRNA reductase by immature tRNAGlu. We further demonstrate that, whereas overexpression of tRNAGlu does not affect tetrapyrrole biosynthesis, reduction of GluTR activity through inhibition by tRNAGlu precursors causes tetrapyrrole synthesis to become limiting in early plant development when active photosystem biogenesis provokes a high demand for de novo chlorophyll biosynthesis. Taken together, our work provides insight into the roles of tRNAGlu at the intersection of protein biosynthesis and tetrapyrrole biosynthesis. copyright, serif 2020 American Society of Plant Biologists. All rights reserved.Members of the light-harvesting complex (LHC) protein family participate in multiple processes connected with light sensing, light absorption and pigment binding within the thylakoid membrane. Amino-acid residues of the light-harvesting chlorophyll a/b binding proteins (LHCPs) involved in pigment binding have been precisely identified through X-ray crystallography experiments. In vitro pigment-binding studies have been performed with light-harvesting-like 3 (LIL3) proteins, and the pigment-binding ability of cyanobacterial high-light inducible proteins (Hlips) has been studied in detail. However, analysis of pigment binding by plant Hlip homologs, called ONE-HELIX PROTEINS (OHPs), is lacking. Here, we report on successful invitro reconstitution of Arabidopsis (Arabidopsis thaliana) OHPs with chlorophylls and carotenoids, and show that pigment binding depends on formation of OHP1/OHP2 heterodimers. Pigment binding capacity was completely lostin each of the OHPs when residues of the LHC chlorophyll-binding motif required for chlorophyll binding were mutated. Moreover, the mutated OHP variants failed to rescue the respective knockout (T-DNA insertion) mutants, indicating that pigment-binding ability is essential for OHP function in vivo. SN-011 in vitro The scaffold protein HIGH CHLOROPHYLL FLUORESCENCE244 (HCF244) is tethered to the thylakoid membrane by the OHP heterodimer. We show that HCF244 stability depends on OHP heterodimer formation and introduce the concept of a functional unit consisting of OHP1, OHP2 and HCF244, in which each protein requires the others. Because of their pigment-binding capacity, we suggest that OHPs function in the delivery of pigments to the D1 subunit of photosystem II. copyright, serif 2020 American Society of Plant Biologists. All rights reserved.The nitrate transport accessory protein OsNAR2 plays a critical role in root-growth responses to nitrate and nitrate acquisition in rice (Oryza sativa). In this study, a pull-down assay combined with yeast two-hybrid and co-immunoprecipitation analyses revealed that OsNAR2.1 interacts with OsNIT1 and OsNIT2. Moreover, an in vitro nitrilase activity assay indicated that indole-3-acetonitrile (IAN) is hydrolyzed to indole-3-acetic acid (IAA) by OsNIT1, the activity of which was enhanced 3-4-fold by OsNIT2 and in excess of 5-8-fold by OsNAR2.1. Knockout (KO) of OsNAR2.1 was accompanied by repressed expression of both OsNIT1 and OsNIT2, whereas KO of OsNIT1 and OsNIT2 in the osnit1 and osnit2 mutant lines did not affect expression of OsNAR2.1 or the root nitrate acquisition rate. osnit1 and osnit2 displayed decreased primary root length and lateral root density. Double KO of OsNAR2.1 and OsNIT2 caused further decreases in lateral root density under nitrate supply . Ammonium supply repressed OsNAR2.1 expression whereas it upregulated OsNIT1 and OsNIT2 expression. Both osnit1 and osnit2 showed root growth hypersensitivity to external ammonium; however, less root growth sensitivity to external IAN, higher expression of three IAA-amido synthetase (GH3) genes, and a lower rate of 3H-IAA movement towards the roots were observed. Taken together, we conclude that the interaction of OsNIT1 and OsNIT2 activated by OsNAR2.1 and nitrogen supply is essential for maintaining root growth possibly via altering the IAA ratio of free to conjugate forms and facilitating its transportation. copyright, serif 2020 American Society of Plant Biologists. All rights reserved.