Requirement of the C ₃ HC ₄ zinc RING finger of the Arabidopsis PEX10 for photorespiration and leaf peroxisome contact with chloroplasts

Abstract

Plant peroxisomes perform multiple vital metabolic processes including lipid mobilization in oil-storing seeds, photorespiration, and hormone biosynthesis. Peroxisome biogenesis requires the function of peroxin (PEX) proteins, including PEX10, a C3HC4 Zn RING finger peroxisomal membrane protein. Loss of function of PEX10 causes embryo lethality at the heart stage. We investigated the function of PEX10 with conditional sublethal mutants. Four T-DNA insertion lines expressing pex10 with a dysfunctional RING finger were created in an Arabidopsis WT background (⌬Zn plants). They could be normalized by growth in an atmosphere of high CO2 partial pressure, indicating a defect in photorespiration. ␤-Oxidation in mutant glyoxysomes was not affected. However, an abnormal accumulation of the photorespiratory metabolite glyoxylate, a lowered content of carotenoids and chlorophyll a and b, and a decreased quantum yield of photosystem II were detected under normal atmosphere, suggesting impaired leaf peroxisomes. Light and transmission electron microscopy demonstrated leaf peroxisomes of the ⌬Zn plants to be more numerous, multilobed, clustered, and not appressed to the chloroplast envelope as in WT. We suggest that inactivation of the RING finger domain in PEX10 has eliminated protein interaction required for attachment of peroxisomes to chloroplasts and movement of metabolites between peroxisomes and chloroplasts.␤-oxidation ͉ biogenesis ͉ glyoxysome E ukaryotic peroxisomes perform multiple metabolic processes, including fatty acid ␤-oxidation and H 2 O 2 inactivation by catalase (1). In plants, leaf peroxisomes interact with chloroplasts and mitochondria in photorespiration, a metabolic pathway in which two molecules of glycolate are converted in a series of enzymatic reactions through glyoxylate, glycine, serine, and hydroxypyruvate into CO 2 and phosphoglycerate (2-4). The advantage of the photorespiratory cycle is twofold. When CO 2 in the plant canopy becomes limited in supply (which is frequent at midday), ribulose-bisphosphate carboxylase/oxygenase functions as an oxygenase and protects the photosynthetic machinery from photodamage. It does so by using energy for respiration, producing CO 2 , and regenerating the substrate to be used in CO 2 fixation. Mutants lacking enzymes of the photorespiratory cycle are incapable of surviving in ambient air but are able to grow normally in atmosphere enriched in CO 2 because ribulosebisphosphate oxygenase is suppressed (2). Plant peroxisomes are necessary for jasmonic acid biosynthesis (5) and are implicated in conversion of indole-3-butyric acid (IBA) into indole-3-acetic acid (IAA) (6-8). Specialized peroxisomes called glyoxysomes contain glyoxylate cycle enzymes for lipid mobilization in germinating oil seedlings and senescing leaves (1).The peroxins (PEX proteins) are a set of cytosolic and membrane proteins involved in peroxisome biogenesis. Mutations of PEX genes leading to impaired peroxisome biogenesis result in severe metabolic and developmental disturbances in yeasts,...

Different functions of the C 3 HC 4 zinc RING finger peroxins PEX10, PEX2, and PEX12 in peroxisome formation and matrix protein import

“…In the PEX10-ΔZn1×GFP-PTS1 hybrids, transcription of both the WT and pex10-ΔZn gene together was much lower ( Fig. S4A) with approximately equal amounts of WT and mutated transcript (19). The PEX10-WT-T7 cDNA in the pex10-KO mutant, which lacks the endogenous WT gene, exhibited a 60-fold higher transcription rate relative to WT (PEX10-WT-T7-pex10-KO; Fig.…”

“…The conditional sublethal mutant expressing pex10 with a dysfunctional zinc finger in the presence of the WT allele (PEX10-ΔZn1) (19) was crossed with WT plants expressing the peroxisome-localized GFP (GFP-PTS1) (20) to analyze photosynthetic yield and photorespiration in the hybrid plants. Pex10, pex2, and pex12 with a dysfunctional zinc finger (Fig.…”

“…The PEX10-ΔZn1 line of our former analysis (19) was crossed with Arabidopsis Columbia WT plants expressing GFP-PTS1 (20), resulting in PEX10-ΔZn1×GFP-PTS1 plants; pex10-ΔZn-T7, pex2-ΔZn-T7, and pex12-ΔZn-T7 cDNAs were constructed with an N-terminal T7 tag and a triple Gly-Ser linker between the T7 tag and the start codon and were transformed into Arabidopsis Columbia GFP-PTS1 WT plants (20). The relative expression level of endogenous and transgenic PEX genes was determined by qRT-PCR (SI Text).…”

Peroxisome Function, Biogenesis, and Dynamics in Plants

“…Given the close metabolic connections between peroxisomes and other organelles, it is not surprising that tight physical associations are observed, for example, among peroxisomes and the ER (Barton et al, 2013) and chloroplasts (Schumann et al, 2007;Oikawa et al, 2015). Peroxules can mediate interorganellar contacts, such as among peroxisomes and ER (Sinclair et al, 2009), oil bodies (Thazar-Poulot et al, 2015), mitochondria (Jaipargas et al, 2016), and chloroplasts (Gao et al, 2016).…”

Función del gen 3-cetoacil-CoA tiolasa 2 (KAT2) en defensa y desarrollo. Participación de los peroxisomas en las respuestas a herida en Arabidopsis thaliana.

“…Como _______________________________________________________________Resultados II se muestra en la figura 37.A, las plantas MFP2::YFP-MFP2 mostraron señales fluorescentes provenientes de la proteína YFP localizadas próximas a los cloroplastos (autofluorescencia roja), correspondiendo cada punto verde con un peroxisoma. Los peroxisomas de plantas se asocian a cloroplastos para poder llevar a cabo la fotorespiración (Somerville, 2001, Schumann et al, 2007. Para analizar si el CFB actúa como un inductor de la proliferación de peroxisomas en Arabidopsis, se comparó la fluorescencia debida a YFP en hojas de plantas tratadas con CFB respecto a hojas de plantas control.…”