Hsp70, sHsps and ubiquitin proteins modulate HsfA6a‐mediated Hsp101 transcript expression in rice (Oryza sativa L.)

Abstract

Hsp100 chaperones disaggregate the aggregated proteins and are vital for maintenance of protein homeostasis. The level of Hsp100 synthesised in the cells has a bearing on the survival of plants under heat stress. The Hsp100 transcription machinery is activated within minutes of the onset of heat stress. The heat shock factor HsfA6a plays a major role in the transcriptional regulation of the Hsp101 gene in rice plants. Through yeast‐2‐hybrid library screening, we identified small heat shock proteins (sHSPs), Hsp70 and ubiquitin as HsfA6a interacting proteins (HIPs). The bimolecular fluorescence complementation assays showed the physical interaction of HsfA6a with Hsp16.9A‐CI and Hsp18.0‐CII in the cytosolic region and with cHsp70‐1 in the nucleus. With the Hsp101 promoter: reporter gene assays, using yeast cells and rice protoplasts, we show that CI‐sHsps and CII‐sHsps are negative regulators and Hsp70 positive regulator of the HsfA6a activity in modulation of Hsp101 transcription. We also noted that the HsfA6a interactors, Hsp70 and CI‐sHsps and CII‐sHsps, physically interact with each other. We noted that HsfA6a binds with the CI‐sHsp and Hsp70 promoters, implying that HsfA6a has a role in transcriptional regulation of its interacting proteins. Furthermore, we noted that the mutation of the ubiquitin/sumoylation acceptor site lysine 10 to alanine (K10A) of HsfA6a enhanced its DNA binding potential on the Hsp101 promoter, implying that these modifiers are possibly involved in modulation of HsfA6a activity. Our work shows that Hsp70, CI‐sHsps and CII‐sHsp, and ubiquitin proteins coordinate with HsfA6a in mediating the Hsp101 transcription process in rice.

Comparative transcriptome analysis of the mechanism difference in heat stress response between indica rice cultivar “IR64” and japonica cultivar “Koshihikari” at the seedling stage

“…Rice OsHSFA2dI participated in the unfolded protein response under HS by alternative splicing (Cheng et al, 2015). HsfA6a mediates transcriptional regulation of the HSP101 gene in rice (Singh et al, 2021). We identified a large number of genes encoding HSPs and Hsfs among the IHR KHR and CHR DEGs, including hsp82A, HSP70, HSP26.7, OsHsfB2b, hsp82B, OsHSP24.1, OsHSP17.7, HSA32, HSP100, OsHsfA2a and some uncloned genes containing heat shock protein typical domains, many of which are core genes in the PPI network.…”

When Size Matters: New Insights on How Seed Size Can Contribute to Plant Developmental Success

“…The role of HSPs in relation to heat stress and seed size was further investigated in tobacco, where 61 HSP70 members have been identified. HSP70 is a highly conserved HSP, acting as the main molecular chaperone in most plants [121]. Indeed, NtHSP70-8 was found to be highly expressed under drought stress conditions, conferring drought tolerance to tobacco when overexpressed [122].…”

Abiotic Stress in Crop Production

“…BcHSFA1, Sly-HSFA1a, ZmHSF05, TaHSFA2e, and OsHSFA2dI are associated with improved heat tolerance and have been identified as activators of HSP expression in rapeseed, tomatoes, maize, wheat, and rice [ 80 , 81 , 82 , 83 , 84 ]. The activity of HSFs can be regulated by heat-shock proteins (HSPs) [ 85 ] and alternative splicing [ 86 ]. The alternative splicing mechanism has been confirmed as a novel component of heat-shock memory in wheat, barley, rice, maize, and tomatoes [ 84 , 87 , 88 , 89 , 90 ].…”