Arabidopsis Seedling Lethal 1 Interacting With Plastid-Encoded RNA Polymerase Complex Proteins Is Essential for Chloroplast Development

Abstract

Mitochondrial transcription termination factors (mTERFs) are highly conserved proteins in metazoans. Plants have many more mTERF proteins than animals. The functions and the underlying mechanisms of plants’ mTERFs remain largely unknown. In plants, mTERF family proteins are present in both mitochondria and plastids and are involved in gene expression in these organelles through different mechanisms. In this study, we screened Arabidopsis mutants with pigment-defective phenotypes and isolated a T-DNA insertion mutant exhibiting seedling-lethal and albino phenotypes [seedling lethal 1 (sl1)]. The SL1 gene encodes an mTERF protein localized in the chloroplast stroma. The sl1 mutant showed severe defects in chloroplast development, photosystem assembly, and the accumulation of photosynthetic proteins. Furthermore, the transcript levels of some plastid-encoded proteins were significantly reduced in the mutant, suggesting that SL1/mTERF3 may function in the chloroplast gene expression. Indeed, SL1/mTERF3 interacted with PAP12/PTAC7, PAP5/PTAC12, and PAP7/PTAC14 in the subgroup of DNA/RNA metabolism in the plastid-encoded RNA polymerase (PEP) complex. Taken together, the characterization of the plant chloroplast mTERF protein, SL1/mTERF3, that associated with PEP complex proteins provided new insights into RNA transcription in the chloroplast.

Identification, Characterization, and Expression Profile Analysis of the mTERF Gene Family and Its Role in the Response to Abiotic Stress in Barley (Hordeum vulgare L.)

“…Notably, the tissue-specific gene HvmTERF16 (mTERF3/SL1, SEEDLING LETHAL 1) was downregulated with 2.65-fold change compared with the control. Since limited studies have been conducted on mTERF genes (Jiang et al, 2020), the biological function of HvmTERFs still need more experimental verification. FPKM+1) transform to represent color scores.…”

“…HvmTERF2, HvmTERF16, and HvmTERF58 (orthologous to RUGOSA2, SL1/mTERF3, and mTERF6 in Arabidopsis, respectively) displayed high expression levels in the studied tissues and stages. In Arabidopsis, these orthologous genes are essential for plant photosynthesis, mitochondrial, and chloroplastic gene expression and development, and leaf patterning and organogenesis (Quesada et al, 2011;Jiang et al, 2020). HvmTERF24 was the most highly expressed gene in different organs.…”

Mitochondrial Transcription Termination Factor 27 Is Required for Salt Tolerance in Arabidopsis thaliana

“…Yeast two-hybrid assays were performed using the yeast strain Y2H Gold (Clontech), following the manufacturer’s instructions. For construction of the Gateway entry clones, PCR products were inserted into pDONR207 via BP reactions (Gateway BP clonase enzyme mix; Invitrogen), then cloned into the expression vectors (pGBKT7 or pGADT7) which contain the attR1-CmR-ccdB-attR2 fragment via LR reactions (Gateway LR clonase enzyme mix; Invitrogen) as previously described [ 46 ]. These vectors were transformed into Y2H Gold yeast (Clontech).…”

PAP8/pTAC6 Is Part of a Nuclear Protein Complex and Displays RNA Recognition Motifs of Viral Origin

“…Although their molecular functions remain largely unknown, PAP8 and PAP12 could be placed between regulation and DNA/RNA metabolism of chloroplast gene transcription; in particular in the control of termination or transcriptional pausing through the binding to mitochondrial transcription termination factors (mTERFs). Indeed, PAP8/pTAC6 was found in additional recruitments at the mTERF5/MDA1-regulated transcriptional pause region of psbEFLJ [ 24 ] and as an interacting protein of GENOMES UNCOUPLED 1 (GUN1), a pentatricopeptide repeats (PPR) protein involved in retrograde signaling [ 25 ], while SL1/mTERF3 interacts with PAP12, PAP5, and PAP7 [ 26 ].…”