Molecular evidence of the involvement of heat shock protein 90 in brassinosteroid signaling in Arabidopsis T87 cultured cells

Abstract

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone that is reportedly involved in the proper folding, stabilization, intracellular trafficking, maintenance and degradation of numerous proteins, as well as the facilitation of cellular signaling in various organisms including plants. Brassinosteroids (BRs), a class of unique steroidal hormones, play crucial roles in plant growth and development. The interaction between HSP90 proteins and BR action has been poorly understood. Here, we present molecular evidence suggesting that HSP90 proteins have a function(s) in BR signal transduction. First, blue native/sodium dodecyl sulfate-polyacrylamide gel electrophoresis linked immunoblotting demonstrated that a bioactive BR, brassinolide (BL), promotes the formation of some HSP90-containing macromolecular complexes with molecular weight more than 480 kDa in Arabidopsis T87 cultured cells. Second, HSP90.3, one of seven Arabidopsis HSP90 family proteins, was observed to interact in vitro with BRI1-EMS-SUPPRESSOR 1 (BES1), a transcription factor acting in BR signaling. Geldanamycin, an inhibitor of ATPase activity in HSP90, not only diminished HSP90.3 interaction with BES1 in vitro, but also suppressed BL-induced down-regulation of two BR biosynthesis genes, CONSTITUTIVE PHOTHOMORPHOGENESIS AND DWARFISM and DWARF4 in vivo. The results suggest the involvement of the HSP90/BES1 heterocomplexes in BR signaling-mediated feedback control in BR contents. Together, our results provide important clues to elucidate HSP90s' functions in the BR signaling pathway in Arabidopsis.

Heat shock protein 90 acts in brassinosteroid signaling through interaction with BES1/BZR1 transcription factor

“…Recently, Samakovli et al (2014) reported that HSP90 interacts with a BR signaling component, BIN2 kinase, to modulate its nuclear retention. Independently of their study, HSP90 was also found to bind to BES1 (Lachowiec et al, 2013;Shigeta et al, 2014). These findings suggest the involvement and importance of HSP90 activity in BR signaling.…”

“…Template DNA of BRASSINAZOLE RESISTANT 1 (BZR1) and HSP90.3 for in vitro transcription was constructed similarly to that of BRASSINOSTEROID INSENSITIVE 1-EMS-SUPRESSOR 1 (BES1) described in Shigeta et al (2014). The templates of truncated BES1 were constructed from its full-length cDNA (pEU-E01-HF-BES1) using the PrimeSTAR Mutagenesis Basal Kit (TaKaRa Bio Inc., Shiga, Japan).…”

“…ecotype Columbia (Axelos et al, 1992). Transgenic T87 cells carrying 35S::6 × His-FLAG-BES1::Nos-T (35S::HF-BES1) was generated and maintained as described in Shigeta et al (2014).…”

Brassinosteroid-induced de novo protein synthesis in Zea mays under salinity and bioinformatic approach for identification of heat shock proteins

“…Important to note that genes coding these chaperones are greatly induced by BRs directly under heat shock, and level of protein products is increased after heat shock (Dhaubhadel et al 2002). Recently, a new evidence was found about role of HSPs, particularly HSP90, in brassinosteroids signaling in Arabidopsis cells (Shigeta et al 2014). It has been shown that Electronic supplementary material The online version of this article (doi:10.1007/s10725-015-0093-3) contains supplementary material, which is available to authorized users.…”

“…Moreover, inhibitor of HSP90 ATPase activity-geldanamycin-suppressed BR-induced downregulation of key biosynthesis genes-CONSTITUTIVE PHOTHOMOR-PHOGENESIS AND DWARFISM (CPD) and DWARF4 in vivo (Shigeta et al 2014). HSP90 also assists nuclear localization of BRs signaling component-BIN2 (BRAS-SINOSTEROID INSENSITIVE 2) protein and geldanamycin treatment force BIN2 translocation to cytosol (Samakovli et al 2014).…”