Structure and activity of JAC1 J-domain implicate the involvement of the cochaperone activity with HSC70 in chloroplast photorelocation movement

Abstract

Chloroplast photorelocation movement towards weak light and away from strong light is essential for plants to adapt to the fluctuation of ambient light conditions. In the previous study, we showed that blue light receptor phototropins mediated blue light-induced chloroplast movement in Arabidopsis by regulating short actin filaments localized at the chloroplast periphery (cp-actin filaments) rather than actin cables in the cytoplasm. However, the signaling pathway for the chloroplast photorelocation movement is still unclear. We also identified JAC1 (J-domain protein required for chloroplast accumulation response 1) as an essential component for the accumulation response and dark positioning in Arabidopsis. We recently determined the crystal structure of the J-domain of JAC1. The JAC1 J-domain has a positively charged surface, which forms a putative interface with the Hsc70 chaperone by analogy to that of bovine auxilin. Furthermore, the mutation of the highly conserved HPD motif in the JAC1 J-domain impaired the in vivo activity of JAC1. These data suggest that JAC1 cochaperone activity with HSC70 is essential for chloroplast photorelocation movement.

Chloroplast Photorelocation Movement: A Sophisticated Strategy for Chloroplasts to Perform Efficient Photosynthesis

“…JAC1 has a J-domain at the C-terminus and is similar to a clathrin uncoating factor, auxilin . The J-domain of JAC1 is necessary for JAC1 function and the crystal structure showed high similarity between that domain and that of the bovine auxilin J-domain Suetsugu et al, 2010c). jac1 mutant plants were completely defective in the accumulation response but retain the avoidance response .…”

Functional relevance of J-protein family of rice (Oryza sativa)

“…Seven-day old seedlings of T-DNA insertion mutant lines j3-1 (Salk_132923) and j3-2 (Salk_141625) of Arabidopsis J3 protein (At3g44110) were given heat stress at 42°C for different duration (1 and 5 unstressed, 2 and 3 stressed; 4 seeds heat stressed). The growth response was scored after 10 days of treatments Chlamydomonas (CDJ2/Hsp70B; Liu et al 2005) and movement of chloroplast in Arabidopsis that has implication in photorelocation of chloroplast (Suetsugu et al 2010). JAC1, the J-protein involved in movement of chloroplast, was functionally impaired if its HPD tripeptide was mutated to AAA (Suetsugu et al 2010).…”

“…The growth response was scored after 10 days of treatments Chlamydomonas (CDJ2/Hsp70B; Liu et al 2005) and movement of chloroplast in Arabidopsis that has implication in photorelocation of chloroplast (Suetsugu et al 2010). JAC1, the J-protein involved in movement of chloroplast, was functionally impaired if its HPD tripeptide was mutated to AAA (Suetsugu et al 2010). It will be worthwhile to assess the role of 21 J-proteins in rice that do not contain HPD motif.…”

Novel Role of JAC1 in Influencing Photosynthesis, Stomatal Conductance, and Photooxidative Stress Signalling Pathway in Arabidopsis thaliana

“…The highly conserved His-Pro-Asp (HPD) tripeptide within J-domain has been shown to facilitate the interactions with Hsp70 chaperones ( Jiang et al., 2003 ). Structural analysis of the JAC1 J-domain indicates that HPD motif is indispensable for JAC1-dependent chloroplast light-induced movement and suggests that JAC1 cooperation with heat shock protein cognate 70 (Hsc70) chaperone is needed in this process ( Suetsugu et al., 2010b ). Auxilin J-domain targets and activates the Hsc70 that mediates clathrin uncoating ( Eisenberg and Greene, 2007 ).…”