Inhibition of Heat Shock proteins HSP90 and HSP70 induce oxidative stress, suppressing cotton fiber development

Abstract

Cotton fiber is a specialized unicellular structure useful for the study of cellular differentiation and development. Heat shock proteins (HSPs) have been shown to be involved in various developmental processes. Microarray data analysis of five Gossypium hirsutum genotypes revealed high transcript levels of GhHSP90 and GhHSP70 genes at different stages of fiber development, indicating their importance in the process. Further, we identified 26 and 55 members of HSP90 and HSP70 gene families in G. hirsutum. The treatment of specific inhibitors novobiocin (Nov; HSP90) and pifithrin/2-phenylethynesulfonamide (Pif; HSP70) in in-vitro cultured ovules resulted in a fewer number of fiber initials and retardation in fiber elongation. The molecular chaperone assay using bacterially expressed recombinant GhHSP90-7 and GhHSP70-8 proteins further confirmed the specificity of inhibitors. HSP inhibition disturbs the H2O2 balance that leads to the generation of oxidative stress, which consequently results in autophagy in the epidermal layer of the cotton ovule. Transmission electron microscopy (TEM) of inhibitor-treated ovule also corroborates autophagosome formation along with disrupted mitochondrial cristae. The perturbations in transcript profile of HSP inhibited ovules show differential regulation of different stress and fiber development-related genes and pathways. Altogether, our results indicate that HSP90 and HSP70 families play a crucial role in cotton fiber differentiation and development by maintaining cellular homeostasis.

Role of GhHDA5 in H3K9 deacetylation and fiber initiation in Gossypium hirsutum

“…However, this is just a predictive model and it requires confirmation by future experimentation. Additionally, the interaction of HDA5 with several HSPs and HSFs is interesting as our group recently described that inhibition of HSP70/HSP90 severely impedes fiber initiation by oxidative stress and autophagy (Sable et al ., ). We also found the enhanced superoxide level and autophagy (Figures a and f, and 7b) marked by higher ATG8 expression and higher H3K9 acetylation on ATG8 promoter in the ovules of GhHDA5 RNAi lines.…”

A multiscale approach reveals regulatory players of water stress responses in seeds during germination

“…HSPs 70 are chaperone proteins that bind ATP in response to stress, and they are also involved in protection against oxidative stress (Pulido, Llamas & Rodriguez‐Concepcion ). In cotton fibre, it has been demonstrated that their inhibition leads to H 2 O 2 accumulation and oxidative stress (Sable et al, ). They have been associated with drought tolerance in Populus (Yer, Baloglu, Ziplar, Ayan, & Unver, ) and Nicotiana tabacum (Cho & Choi, ).…”

Impaired expression of chloroplast HSP90C chaperone activates plant defense responses leading to a disease symptom-like phenotype

“…Heat shock proteins or HSPs are a group of multiple protein families, which are induced upon different cellular stresses and help cells survive under stressed condition (Parsell and Lindquist, 1994). HSPs are evolutionarily conserved throughout the prokaryotes and eukaryotes and have been classified into different families, including HSP100, HSP90, HSP70, HSP60, HSP40, and HSP20 (Park and Seo, 2015; Sable et al ., 2018). All of these families help maintain cellular homeostasis and play roles in different developmental processes through their molecular chaperone function (Park and Seo, 2015; Sable et al ., 2018).…”

“…HSPs are evolutionarily conserved throughout the prokaryotes and eukaryotes and have been classified into different families, including HSP100, HSP90, HSP70, HSP60, HSP40, and HSP20 (Park and Seo, 2015; Sable et al ., 2018). All of these families help maintain cellular homeostasis and play roles in different developmental processes through their molecular chaperone function (Park and Seo, 2015; Sable et al ., 2018). Out of these families, HSP90 family proteins have been shown to play pleiotropic roles in diverse biological phenomena.…”