AKRP and EMB506 are two ankyrin repeat proteins essential for plastid differentiation and plant development in Arabidopsis

Abstract

SummaryEMB506 is a chloroplast protein essential for embryo development, the function of which is unknown. A twohybrid interaction screen was performed to provide insight into the role of EMB506. A single interacting partner, AKRP, was identified among a cDNA library from immature siliques. The AKR gene (Zhang et al., 1992, Plant Cell 4, 1575-1588) encodes a protein containing five ankyrin repeats, very similar to EMB506. Protein truncation series demonstrated that both proteins interact through their ankyrin domains. Using reverse genetics, we showed that loss of akr function resulted in an embryo-defective (emb) phenotype indistinguishable from the emb506 phenotype. Transient expression of the signal peptide of AKRP fused to green fluorescent protein demonstrated the chloroplast localization of AKRP. The ABI3 promoter was used to express AKR in a seed-specific manner in order to analyse the post-embryonic effect of AKR loss of function in akr/akr seedlings. Homozygous fertile and viable akr/akr plants were obtained. These plants exhibited mild to severe defects in chloroplast and leaf cellular organization. We conclude that EMB506 and AKRP are involved in crucial and tightly controlled events in plastid differentiation linked to cell differentiation, morphogenesis and organogenesis during the plant life cycle.

Inducible Knockdown of MONOGALACTOSYLDIACYLGLYCEROL SYNTHASE1 Reveals Roles of Galactolipids in Organelle Differentiation in Arabidopsis Cotyledons

“…Considering that cell proliferation for cotyledon formation is nearly completed during embryogenesis and the cell expansion mainly contributes to the postgerminative cotyledon growth in the light (Tsukaya et al, 1994;StoynovaBakalova et al, 2004), the morphological disorder and the dwarf phenotype in the white L4 cotyledons may be due to distorted mesophyll cell expansion during postgerminative growth. The distorted organization of mesophyll cells has been observed in several mutants with defective chloroplast development (Wang et al, 2000;Wycliffe et al, 2005;Garcion et al, 2006;Sulmon et al, 2006), including the mgd1-2 mutant (Kobayashi et al, 2007), thus showing a tight developmental link between chloroplasts and host mesophyll cells. Furthermore, application of norflurazon, which inhibits carotenoid biosynthesis and impairs chloroplast development, to Arabidopsis seedlings was recently found to affect the transition of leaf cells from the proliferation stage to the expansion stage, thus resulting in decreased cell size in young true leaves (Andriankaja et al, 2012).…”

Global Analysis Reveals the Crucial Roles of DNA Methylation during Rice Seed Development

“…LOC_Os02g29140 is an ankyrin repeat-containing protein possibly mediating protein-protein interactions among diverse groups of proteins, including those involved in signal transduction, cytoskeleton interactions, and regulation of the cell cycle; mutation of its homologs ANKYRIN REPEAT PROTEIN and EMBRYO-DEFECTIVE506 results in defective embryo development at the globular stage (Garcion et al, 2006).…”

Identification of QTLs associated with albino plant formation and some new facts concerning green versus albino ratio determinants in triticale (×Triticosecale Wittm.) anther culture

“…One of them was gene with homology to DAG, which is essential for chloroplast development from proplastids, and acts very early in chloroplast development (Chatterjee et al 1996). The second gene encoded a class B ankyrin repeat protein, which is involved in plastid differentiation (Garcion et al 2006). The third one was a transcription factor, that encodes abscisic acid-insensitive 3 (ABI3), which is important for plastid identity and could influence on plastid ultrastructure (Rohde et al 2000).…”