Tobacco class I cytosolic small heat shock proteins are under transcriptional and translational regulations in expression and heterocomplex prevails under the high‐temperature stress condition in vitro

• Published in: Plant, cell and environment cell and environment, 2015-04, Vol.38 (4), p.767-776
• Main Authors: PARK, SOO MIN, KIM, KEUN PILL, JOE, MYUNG KUK, LEE, MI OK, KOO, HYUN JO, HONG, CHOO BONG
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acids; atomic force microscopy; citrate (si)-synthase; clones; Cytosol - metabolism; Escherichia coli; family member; Gene Expression Regulation, Plant; Gene Library; genes; Genes, Reporter; heat shock proteins; Heat-Shock Proteins, Small - genetics; Heat-Shock Proteins, Small - isolation & purification; Heat-Shock Proteins, Small - metabolism; Heat-Shock Response; Hot Temperature; luciferase; molecular chaperone; Molecular Chaperones - genetics; Molecular Chaperones - isolation & purification; Molecular Chaperones - metabolism; Molecular Sequence Data; Multiprotein Complexes; Nicotiana - genetics; Nicotiana - physiology; Nicotiana tabacum; open reading frames; Plant Proteins - genetics; Plant Proteins - isolation & purification; Plant Proteins - metabolism; polyacrylamide gel electrophoresis; post‐transcriptional differentiation; Sequence Alignment; Temperature; temperature dependence; tobacco; transcription (genetics); transcriptional differentiation; translation (genetics)
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12436

Seven genomic clones of tobacco (Nicotiana tabacum W38) cytosolic class I small heat shock proteins (sHSPs), probably representing all members in the class, were isolated and found to have 66 to 92% homology between their nucleotide sequences. Even though all seven sHSP genes showed heat shock‐responsive accumulation of their transcripts and proteins, each member showed discrepancies in abundance and timing of expression upon high‐temperature stress. This was mainly the result of transcriptional regulation during mild stress conditions and transcriptional and translational regulation during strong stress conditions. Open reading frames (ORFs) of these genomic clones were expressed in Escherichia coli and the sHSPs were purified from E. coli. The purified tobacco sHSPs rendered citrate synthase and luciferase soluble under high temperatures. At room temperature, non‐denaturing pore exclusion polyacrylamide gel electrophoresis on three sHSPs demonstrated that the sHSPs spontaneously formed homo‐oligomeric complexes of 200 ∼ 240 kDa. However, under elevated temperatures, hetero‐oligomeric complexes between the sHSPs gradually prevailed. Atomic force microscopy showed that the hetero‐oligomer of NtHSP18.2/NtHSP18.3 formed a stable oligomeric particle similar to that of the NtHSP18.2 homo‐oligomer. These hetero‐oligomers positively influenced the revival of thermally inactivated luciferase. Amino acid residues mainly in the N‐terminus are suggested for the exchange of the component sHSPs and the formation of dominant hetero‐oligomers under high temperatures.