Knockdown of CaHSP60-6 confers enhanced sensitivity to heat stress in pepper (Capsicum annuum L.)

• Published in: Planta Vol. 250; no. 6; pp. 2127 - 2145
• Main Authors: ul Haq, Saeed, Khan, Abid, Ali, Muhammad, Gai, Wen-Xian, Zhang, Huai-Xia, Yu, Qing-Hui, Yang, Sheng-Bao, Wei, Ai-Min, Gong, Zhen-Hui
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Science + Business Media 01.12.2019; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Abiotic stress; Agriculture; Antioxidants; Bioinformatics; Biological activity; Biological evolution; Biomedical and Life Sciences; Capsicum - genetics; Capsicum - growth & development; Capsicum annuum; Chlorophyll; Chlorophyll - metabolism; Ecology; Electrolyte leakage; Enzymatic activity; Enzyme activity; Evolutionary genetics; Flowers; Forestry; Functional analysis; Gene expression; Gene Expression Regulation, Plant - drug effects; Gene mapping; Gene regulation; Genes; Heat shock proteins; Heat stress; Heat tolerance; Heat treatment; Heat-Shock Response - genetics; HSP60 gene; Hsp60 protein; Introns; Life Sciences; Lipid peroxidation; Lipids; Mannitol; Mapping; Methyl jasmonate; ORIGINAL ARTICLE; Peppers; Peroxidation; Phylogeny; Plant growth; Plant Leaves - metabolism; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Sciences; Protein folding; Reactive oxygen species; Regulatory sequences; Ribonucleic acid; RNA; Salicylic acid; Sensitivity analysis; Sensitivity enhancement; Sodium chloride; Stress, Physiological - genetics; Transcription; Vegetables; Gene silencing; Hormonal application; Abiotic stresses; Gene expression; genes; Pepper; HSP60 genes
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-019-03290-4

The 60 kDa heat shock protein (HSP60) also known as chaperonin (cpn60) is encoded by multi-gene family that plays an important role in plant growth, development and in stress response as a molecular chaperone. However, little is known about the HSP60 gene family in pepper (Capsicum annuum L.). In this study, 16 putative pepper HSP60 genes were identified through bioinformatic tools. The phylogenetic tree revealed that eight of the pepper HSP60 genes (50%) clustered into group I, three (19%) into group II, and five (31%) into group III. Twelve (75%) CaHSP60 genes have more than 10 introns, while only a single gene contained no introns. Chromosomal mapping revealed that the tandem and segmental duplication events occurred in the process of evolution. Gene ontology enrichment analysis predicted that CaHSP60 genes were responsible for protein folding and refolding in an ATP-dependent manner in response to various stresses in the biological processes category. Multiple stress-related cis-regulatory elements were found in the promoter region of these CaHSP60 genes, which indicated that these genes were regulated in response to multiple stresses. Tissue-specific expression was studied under normal conditions and induced under 2 h of heat stress measured by RNA-Seq data and qRT-PCR in different tissues (roots, stems, leaves, and flowers). The data implied that HSP60 genes play a crucial role in pepper growth, development, and stress responses. Fifteen (93%) CaHSP60 genes were induced in both, thermo-sensitive B6 and thermo-tolerant R9 lines under heat treatment. The relative expression of nine representative CaHSP60 genes in response to other abiotic stresses (cold, NaCl, and mannitol) and hormonal applications [ABA, methyl jasmonate (MeJA), and salicylic acid (SA)] was also evaluated. Knockdown of CaHSP60-6 increased the sensitivity to heat shock treatment as documented by a higher relative electrolyte leakage, lipid peroxidation, and reactive oxygen species accumulation in silenced pepper plants along with a substantial lower chlorophyll content and antioxidant enzyme activity. These results suggested that HSP60 might act as a positive regulator in pepper defense against heat and other abiotic stresses. Our results provide a basis for further functional analysis of HSP60 genes in pepper.