## 1 Introduction  
Terrestrial plants face diverse abiotic and biotic stresses during their life cycles. To cope with these environmental stresses, plants employ various important defense-associated proteins, such as pathogenesis-related (PR) proteins (chitinase, glucanase, thaumatin, defensin, and thionin), stress-resistant peptides, and highly efficient defense signaling systems. Among the defense-related proteins, tetratricopeptide (TPR) repeat proteins, which mediate protein-protein interactions, assemble as multiprotein complexes to defend against external stresses [1; 2; 3]. The _Arabidopsis thaliana_ genome encodes more than 16 TPR-containing proteins. Previously, TPR motifs were detected in the FKBP52 protein, which facilitates the folding of target proteins with the help of heat shock protein 90 (HSP90) [4], and in cyclophilin 40 (CyP40), a cyclosporine A-binding immunophilin that supports protein stability and refolding of protein aggregates through the action of its hydrophobic regions [5]. In addition, CHIP, a ubiquitin E3-ligase protein containing three TPR repeats and a U-box domain, protects membrane channel proteins and degrades damaged proteins under extreme temperature conditions [6; 7]. In _Arabidopsis_, TPR motif-containing proteins have been reported to function in the regulation of plant growth and development and hormone signaling [8]. Thus, the TPR-repeat thioredoxin (Trx)-like 1 (TTL1) protein affects abscisic acid (ABA) sensitivity and osmotic stress responses in plants [9]. Ectopic expression of the _spindly_ (_SPY_) gene showed that SPY functions as a negative regulator of gibberell (GA) response, affecting hypocotyl elongation and flowering time in plants [10]. In rice (_Oryza sativa_ L.), the Trx-like protein OsTDX, which contains three N-terminal TPR motifs and a C-terminal Trx domain, exhibits defense activity against various fungal pathogens [11]. Moreover, OsTPR1 participates in the immune response by disturbing the interaction between chitin and MoChia1, a suppressor of chitin-triggered plant immunity [12].  
In contrast to other types of _Arabidopsis_ TPRs, AtTPR10 contains seven N-terminal repeats of the ankyrin (ANK) domain and three C-terminal repeats of the TPR domain. Similar to the TPR motifs, the ANK repeat domains mediate protein-protein interaction in diverse organisms including eukaryotes, prokaryotes, and some viruses [13; 14]. The domains also contain several conserved hydrophobic residues necessary for maintaining their secondary and tertiary structures [15; 16; 17]. Genomic analyses revealed a total of 509 ANK repeats in more than 100 proteins in _Arabidopsis_ with structurally similar characteristics. The ANK repeat-containing plant proteins regulate the cell cycle, mitochondrial enzyme activity, ion transport, and signal transduction [13].  
These data suggest that the two domains play diverse physiological roles in plants by associating with different partner proteins. Although the AtTPR10 protein consists of two highly important domains (TPR and ANK) in a single polypeptide structure, its molecular function remains unknown. Here, we performed bioinformatics analysis of _AtTPR10_ gene expression and investigated the biochemical characteristics of the AtTPR10 protein. Our results show that AtTPR10 functions as a molecular chaperone to protect plants from diverse abiotic stresses that can be used for the development of stress-tolerant crops.