Chloroplast- or Mitochondria-Targeted DEAD-Box RNA Helicases Play Essential Roles in Organellar RNA Metabolism and Abiotic Stress Responses

Abstract

The yields and productivity of crops are greatly diminished by various abiotic stresses, including drought, cold, heat, and high salinity. Chloroplasts and mitochondria are cellular organelles that can sense diverse environmental stimuli and alter gene expression to cope with adverse environmental stresses. Organellar gene expression is mainly regulated at posttranscriptional levels, including RNA processing, intron splicing, RNA editing, RNA turnover, and translational control, during which a variety of nucleus-encoded RNA-binding proteins (RBPs) are targeted to chloroplasts or mitochondria where they play essential roles in organellar RNA metabolism. DEAD-box RNA helicases (RHs) are enzymes that can alter RNA structures and affect RNA metabolism in all living organisms. Although a number of DEAD-box RHs have been found to play important roles in RNA metabolism in the nucleus and cytoplasm, our understanding on the roles of DEAD-box RHs in the regulation of RNA metabolism in chloroplasts and mitochondria is only at the beginning. Considering that organellar RNA metabolism and gene expression are tightly regulated by anterograde signaling from the nucleus, it is imperative to determine the functions of nucleus-encoded organellar RBPs. In this review, we summarize the emerging roles of nucleus-encoded chloroplast- or mitochondria-targeted DEAD-box RHs in organellar RNA metabolism and plant response to diverse abiotic stresses.

The DEAD-box RNA Helicase RH50 Is a 23S-4.5S rRNA Maturation Factor that Functionally Overlaps with the Plastid Signaling Factor GUN1

“…4B). Several previous studies have suggested that RNA helicases play a pivotal role in plant stress responses (Liu et al, 2002;Owttrim, 2006;Vashisht and Tuteja, 2006;Kant et al, 2007;Nawaz and Kang, 2017). Because these enzymes mediate localized unwinding of RNAs, they might well become critical at low temperatures, which are expected to stabilize RNA secondary structure (Herschlag, 1995;Jones and Inouye, 1996;Lorsch, 2002).…”

The coordinated action of PPR4 and EMB2654 on each intron half mediates trans‐splicing of rps12 transcripts in plant chloroplasts

“…Chloroplast gene expression is regulated mainly at post‐transcriptional levels, including pre‐mRNA splicing, RNA editing and RNA degradation, processes for which a variety of RNA‐binding proteins (RBPs) are vital (Jacobs and Kück, ; Germain et al ., ). In particular, many nucleus‐encoded RBPs are targeted to the chloroplast and play essential roles in the splicing of chloroplast introns (Jenkins et al ., ; Barkan et al ., ; Falcon de Longevialle et al ., ; Bryant et al ., ; Nawaz and Kang, ).…”

OsSLC1 Encodes a Pentatricopeptide Repeat Protein Essential for Early Chloroplast Development and Seedling Survival

“…However, the ability of these introns to perform self-splicing in vivo has been lost, and thus additional nuclear-and/or plastid-encoded splicing cofactors are required to accomplish intron splicing (Bonen and Vogel 2001;de Longevialle et al 2010). Such cofactors include the plastid maturase matK, chloroplast RNA splicing and ribosome maturation proteins, pentatricopeptide repeat (PPR) proteins, RNA helicases, mitochondrial transcription termination factors, a RNase III domain-containing protein, WHAT IS THIS FACTOR 1 (WTF1) and a WHY and UMP kinase (de Longevialle et al 2010;Quesada 2016;Nawaz and Kang 2017;Schmid et al 2019). Of these cofactors, PPR proteins not only play vital roles in intron splicing, but also in RNA editing, RNA processing, RNA stability and RNA translation (Barkan and Small 2014).…”