Nucleolar GTP-binding protein 1 (NOG1) is a highly conserved GTPase first reported in Trypanosoma as required for ribosome biogenesis. We characterized NbNOG1, a Nicotiana benthamiana NOG1 ortholog sharing more than 45% amino acid identity with Trypanosoma, yeast, and human NOG1. N. benthamiana plants silenced for NbNOG1 were stunted and produced sterile flowers. NbNOG1 is functionally interchangeable with yeast NOG1 (ScNOG1), rescuing yeast lethality caused by loss of ScNOG1. Finally, NbNOG1 silencing caused over-accumulation of pre-rRNA processing intermediates, and concomitant loss of mature rRNAs. Collectively, these data support a role for NbNOG1 in ribosomal RNA processing.

Salicylic acid (SA) is an essential defence hormone in plants. Upon pathogen infection, induced biosynthesis of SA is mediated by Isochorismate synthase 1 (ICS1), whose gene transcription is controlled mainly through two redundant transcription factors, SAR Deficient 1 (SARD1) and Calmodulin-binding protein 60-like g (CBP60g). Although these master transcription factors regulate not only positive, but also negative regulators of immunity, how they control signaling events downstream of different immune receptors is unclear. Using autoimmune mutants activating immunity mediated by different receptors we show that, although the sard1 cbp60g double mutant almost fully suppresses the activation of defence mediated by suppressor of npr1-1, constitutive 2 (snc2), it strikingly enhances snc1, which carries a gain-of-function mutation in an intracellular nucleotide-binding leucine-rich repeat (NLR) immune receptor. This negative regulation of immunity is achieved through the transcriptional regulation of negative regulators, such as Nudix hydrolase homolog 6 (NUDT6). Our study highlights the diverse roles, especially the negative ones, in the regulation of plant immunity by the two master immune transcription factors SARD1 and CBP60g.

Peroxisomes compartmentalize a dynamic suite of biochemical reactions and play a central role in plant metabolism, such as the degradation of hydrogen peroxide, metabolism of fatty acids, photorespiration, and the biosynthesis of plant hormones. Plant peroxisomes have been traditionally classified into three major subtypes, and in-depth mass spectrometry (MS)-based proteomics has been performed to explore the proteome of the two major subtypes present in green leaves and etiolated seedlings. Here, we carried out a comprehensive proteome analysis of peroxisomes from Arabidopsis leaves given a 48-h dark treatment. Our goal was to determine the proteome of the third major subtype of plant peroxisomes from senescent leaves, and further catalog the plant peroxisomal proteome. We identified a total of 111 peroxisomal proteins and verified the peroxisomal localization for six new proteins with potential roles in fatty acid metabolism and stress response by in vivo targeting analysis. Metabolic pathways compartmentalized in the three major subtypes of peroxisomes were also compared, which revealed a higher number of proteins involved in the detoxification of reactive oxygen species in peroxisomes from senescent leaves. Our study takes an important step towards mapping the full function of plant peroxisomes.

Increasing evidence indicates that long non-coding RNAs (lncRNAs) play pivotal roles in regulatory networks controlling plant and animal gene expression. However, lncRNA roles in regulating rubber biosynthesis in Eucommia ulmoides, an emerging source of natural rubber (Eu-rubber), are currently unknown. Here, we report on RNA deep-sequencing of E. ulmoides fruits at two developmental stages. Based on application of a stringent pipeline, 29,103 lncRNAs and 9,048 transcripts of uncertain coding potential (TUCPs) were identified. Two differentially expressed (DE) TUCPs appear to simultaneously regulate 12 protein-coding genes involved in Eu-rubber biosynthesis (GIEBs), as well as 95 DE genes. Functional categorization of these 95 DE genes indicated their involvement in subcellular microstructures and cellular processes, such as cell wall, cell division, and growth. These DE genes may participate in the differentiation and development of laticifers, where Eu-rubber is synthesized. A model is proposed in which “commanders” (DE TUCPs) direct the “builders” (DE genes) to construct a “storehouse” of materials needed for Eu-rubber synthesis, and the “workers” (GIEBs) to synthesize Eu-rubber. These findings provide insights into both cis- and trans-polyisoprene biosynthesis in plants, laying the foundation for additional studies of this crucial process.