The Role of E3 Ubiquitin Ligases in Chloroplast Function

Abstract

Chloroplasts are ancient organelles responsible for photosynthesis and various biosynthetic functions essential to most life on Earth. Many of these functions require tightly controlled regulatory processes to maintain homeostasis at the protein level. One such regulatory mechanism is the ubiquitin-proteasome system whose fundamental role is increasingly emerging in chloroplasts. In particular, the role of E3 ubiquitin ligases as determinants in the ubiquitination and degradation of specific intra-chloroplast proteins. Here, we highlight recent advances in understanding the roles of plant E3 ubiquitin ligases SP1, COP1, PUB4, CHIP, and TT3.1 as well as the ubiquitin-dependent segregase CDC48 in chloroplast function.

Integrated Metabolomic and Transcriptomic Analysis of the Quinoa Seedling Response to High Relative Humidity Stress

“…We also screened five possible long-lasting response genes in the resistant materials based on combined WGCNA and PPI analyses. Among them were identified LOC110722395 (phosphoglycerate kinase, chloroplastic), LOC110733932 (chlorophyll synthase, chloroplastic), and LOC110736961 (E3 ubiquitin-protein ligase), which are associated with chloroplasts [ 83 ]; LOC110706418 (serine hydroxymethyltransferase, mitochondrial), which is associated with mitochondria; and LOC110718123 (heat shock factor protein HSF24), which is associated with stress. Hence, these longevity genes in highly resistant materials are associated with photosynthesis, energy metabolism, and stress response.…”

Combined analysis of lipidomics and transcriptomics revealed the key pathways and genes of lipids in light-sensitive albino tea plant (Camellia sinensis cv. Baijiguan)

“…HY5 , a transcription factor of the bZIP class, is located downstream of photoreceptors and transmits light signals to downstream acting-elements. Under light and dark changes, the dynamic processes of HY5 , COP1 and ABI4 in the nucleus and cytoplasm regulate the key genes of many tetrapyrrole synthetases, such as PORA , HEMA2 and FC2 ( Burko et al., 2020 ; Hand and Shabek, 2022 ). Therefore, this will affect the chlorophyll biosynthesis process.…”

Does the Ubiquitination Degradation Pathway Really Reach inside of the Chloroplast? A Re-Evaluation of Mass Spectrometry-Based Assignments of Ubiquitination

“…There are two E1 and eight E2 ligases and a large number (∼1400) of E3 UBI ligases in A. thaliana that can be found in the cytosol and nucleus or associated with the cytosolic surface of the endoplasmic reticulum or outer membranes of plastids/chloroplasts, mitochondria, and peroxisomes. , Each E3 ligase is generally believed to target a specific set of substrates, and it is therefore the E3 ligases that provide selectivity to proteasomal degradation (in case of polyubiquitinated substrates). Two E3 ligases, SP1 and SP2, are associated with the cytosolic side of chloroplasts. − Furthermore, nuclear-encoded chloroplast precursor proteins synthesized in the cytosol can be polyubiquitinated for proteasomal degradation en route to the chloroplast by cytosolic E3 ligases such as CHIP, and the cytosolic E3 ligase PUB4 appears also involved in chloroplast proteostasis. − However, so far, none of the E1–E2–E3 proteins are known to reside within the plastid/chloroplast stroma and thylakoids.…”

“…There are two E1 and eight E2 ligases and a large number (∼1400) of E3 UBI ligases in A. thaliana 6 that can be found in the cytosol and nucleus or associated with the cytosolic surface of the endoplasmic reticulum or outer membranes of plastids/ chloroplasts, mitochondria, and peroxisomes. 6,14 Each E3 ligase is generally believed to target a specific set of substrates, and it is therefore the E3 ligases that provide selectivity to proteasomal degradation (in case of polyubiquitinated substrates). Two E3 ligases, SP1 and SP2, are associated with the cytosolic side of chloroplasts.…”