1 and 2, B and D). Open in a separate window Figure 2. Subcellular localization of CHUP1-GFP and GFP-CHUP1. the chloroplast outer envelope and the C terminus facing the cytosol, is essential for CHUP1 function, and the coiled-coil region of CHUP1 helps prevent chloroplast aggregation and participates in chloroplast relocation movement. The intracellular distribution of organelles is essential for optimizing metabolic activities in flower cells; hence, the mechanisms by which organelles move to their appropriate positions have long been investigated (Wada and Suetsugu, 2004). Chloroplast movement for efficient light absorption is BI-671800 the most exactly analyzed of these phenomena, because of the importance of photosynthesis (Zurzycki, 1955; Takemiya et al., 2005). Chloroplasts switch their position dynamically according to the ambient light intensity. Under fragile light conditions, chloroplasts gather in the plasma membrane along the periclinal cell wall in palisade cells (the build up response) in order to receive ideal sunlight exposure for efficient photosynthesis. In contrast, under strong light conditions, chloroplasts are positioned in the plasma membrane Rabbit polyclonal to AKR7A2 along the anticlinal cell walls (the avoidance response) to avoid photodamage to the photosynthetic machinery (Kagawa and Wada, 2000; Kasahara et al., 2002; Wada et al., 2003). Hence, chloroplast movement is essential for vegetation to get energy securely and efficiently under numerous light conditions. Chloroplast placing in the dark is also known, but the patterns BI-671800 vary with flower species and cells (Suetsugu et al., 2005). Light-induced chloroplast relocation movement has been analyzed using BI-671800 physiological methods in various flower varieties, including green algae (Haupt et al., 1969; Kraml et al., 1988), mosses (Kagawa et al., 1996; Kadota et al., 2000; Sato et al., 2001), ferns (Yatsuhashi et al., 1985; Yatsuhashi and Kobayashi, 1993; Kagawa and Wada, 1996), and angiosperms (Trojan and Gabrys, 1996; Kagawa and Wada, 2000; Takagi, 2003). Recently, genetic methods using Arabidopsis (and in animal cells (Gouin et al., 2005). Rab27 within the melanosome surface regulates a engine protein for melanosome movement (Wu et al., 2002). These good examples suggest that the key proteins for chloroplast relocation movement may also exist within the chloroplast surface. Previously, we isolated the mutant (Oikawa et al., 2003), which shows aggregation of chloroplasts at the bottom of cells and lacks chloroplast relocation reactions to any light conditions. The gene encodes a protein with several putative functional areas that are related to actin polymerization and might be involved in chloroplast relocation movement. CHUP1 is thought to be the only protein among the recently found proteins related to chloroplast movement (such as JAC1, PMI1, PMI2, and PMI15) that localizes within the chloroplast envelope (Oikawa et al., 2003; Schmidt von Braun and Schleiff, 2008). However, the actual localization of full-length CHUP1 BI-671800 remains unclear. Furthermore, it is also not clear whether these expected functional regions of CHUP1 actually function physiologically to regulate chloroplast relocation downstream of the photoreceptor transmission cascade. In this study, we focused on CHUP1 function from your viewpoint of its localization. We found that full-length CHUP1 localizes within the outer envelope of chloroplasts and that this localization is essential for CHUP1 function. Furthermore, we found that the CHUP1 protein consists of three functional areas: a chloroplast translocation transmission in the N terminus, a region that anchors the chloroplast to the plasma membrane and has a coiled-coil character, and a cytoskeleton-associated region. Here, we statement that CHUP1 is definitely targeted to chloroplasts and has the novel physiological function of regulating chloroplast localization by anchoring chloroplasts to the plasma membrane and forming a bridge to the actin cytoskeleton. RESULTS Detection of CHUP1 in an Isolated Chloroplast Portion To determine the subcellular localization of the full-length CHUP1 biochemically, we performed immunoblot analyses of whole leaves and isolated chloroplasts using two different polyclonal antibodies, one against the N-terminal (head) 200 to 320 amino acids (vegetation (Fig. 1B). The CHUP1 transmission was also recognized in the purified chloroplast portion from wild-type vegetation (Fig. 1C). Interestingly, CHUP1 protein was not recognized after treatment of isolated chloroplasts with the protease thermolysin (Fig. 1D). The transport protein Toc159, which is also sensitive to thermolysin, is localized.