The Arabidopsis PEX12 Gene Is Required for Peroxisome Biogenesis and Is Essential for Development

Abstract

(J.C.) Peroxisomes perform diverse and vital functions in eukaryotes, and abnormalities in peroxisomal function lead to severe developmental disorders in humans. Peroxisomes are also involved in a wide array of physiological and metabolic functions unique to plants, yet many aspects of this important organelle are poorly understood. In yeast and mammals, various steps in peroxisome biogenesis require the function of peroxin (PEX) proteins, among which PEX12 is a RING finger peroxisomal membrane protein involved in the import of matrix proteins. To investigate the role of PEX12 in plants, we identified a T-DNA knockout allele of PEX12 and generated partial loss-of-function pex12 mutants using RNA interference. We show that pex12 null mutants are developmentally arrested during early embryogenesis, and that the embryo-lethal phenotype can be rescued by overexpression of the PEX12-cyan fluorescent protein fusion protein, which targets to the peroxisome. Using virus-induced gene-silencing techniques, we demonstrate that peroxisomal number and fluorescence of the yellow fluorescent proteinperoxisome targeting signal type 1 protein are greatly reduced when PEX12 is silenced. RNA interference plants with partial reduction of the PEX12 transcript exhibit impaired peroxisome biogenesis and function, inhibition of plant growth, and reduced fertility. Our work provides evidence that the Arabidopsis (Arabidopsis thaliana) PEX12 protein is required for peroxisome biogenesis and plays an essential role throughout plant development.Peroxisomes perform diverse and crucial functions in eukaryotes, and peroxisomal deficiencies cause developmental disorders in humans and disrupt many physiological and developmental processes in fungi (Powers and Moser, 1998;Gould and Valle, 2000;Parsons et al., 2001;Titorenko and Rachubinski, 2004). Plant peroxisomes, which include glyoxysomes, leaftype peroxisomes, and unspecialized peroxisomes, contain different sets of enzymes depending on the cell type and developmental stage. They are involved in a wide range of functions, including lipid metabolism, photorespiration, nitrogen metabolism, stress response, and synthesis of some plant hormones (Beevers, 1979;Olsen and Harada, 1995;Hayashi and Nishimura, 2003).More than 30 yeast genes have been identified that encode components for various aspects of peroxisome biogenesis, including peroxisome assembly, matrix protein import, and peroxisome proliferation (Purdue and Lazarow, 2001;Charlton and Lopez-Huertas, 2002;Brown and Baker, 2003). Proteins in this category are named peroxins, or PEX proteins. The peroxisome protein import machinery is composed of a number of proteins facilitating the import process, although the architecture of this machinery is still elusive. PEX2, PEX10, and PEX12 are RING finger proteins hypothesized to function in close proximity to facilitate the import of cargo proteins and the recycling of receptors in yeast and mammals, and possibly in other eukaryotes. These three peroxins are integral membrane proteins whose N...

Light Induces Peroxisome Proliferation in Arabidopsis Seedlings through the Photoreceptor Phytochrome A, the Transcription Factor HY5 HOMOLOG, and the Peroxisomal Protein PEROXIN11b

“…Consistent with this finding, we found more (basal) elongated peroxisomes in the dark-grown cotyledon cells than in adult tissue (observed in our previous studies, such as Fan et al [2005] and Orth et al [2007]). This observation suggests that peroxisomes divide at a higher rate in 3-d seedlings due to the active growth of seedlings at this stage.…”

“…These YFP-PTS1 plants displayed fluorescently labeled peroxisomes as numerous punctate structures in virtually all cell types (Fan et al, 2005;Orth et al, 2007). Three-day-old YFP-PTS1 seedlings grown in the dark were illuminated with 70 mmol m 22 s 21 continuous white light for different time intervals and scored for obvious alterations in size, shape, and abundance of peroxisomes in cotyledon cells with a confocal laser-scanning microscope.…”

Peroxisomes Are Required for in Vivo Nitric Oxide Accumulation in the Cytosol following Salinity Stress of Arabidopsis Plants

“…On the other hand, it has been established that Pex12 is not only required for peroxisome biogenesis but is also essential for plant development (Fan et al, 2005). This could plausibly be explained by Pex12's effect on the import of the peroxisomal NO-generating protein given that NO is also involved in plant germination and development processes Corpas et al, 2006).…”

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

“…PEX10 and PEX12 can interact with PEX5 in mammals (14,15). Impairment of PEX5 ubiquitination and thus of receptor recycling should lead to impaired peroxisomal matrix protein import.In Arabidopsis, the lack of any of the RING finger peroxins results in embryo lethality (10,(16)(17)(18). We started to elucidate the function of these peroxins using conditional sublethal mutants of PEX10.…”