Abstract
FES1A is a heat shock protein 70 binding protein. Mutation of FES1A leads to a defect in thermotolerance of Arabidopsis; however, independent fes1a mutants exhibit a range in the extent of thermosensitivity. Here, we found that BRF2, a gene adjacent to FES1A and encoding a component of transcription factor IIIB, affects the thermosensitivity of fes1a mutants. Knockout of BRF2 suppressed fes1a thermosensitivity, while overexpression of BRF2 increased thermosensitivity of fes1a. BRF2 in fes1a mutants regulates the transcriptional strength of RNA Polymerase II and accumulation of heat shock proteins and eventually affects the thermotolerance of fes1a. There is a cross-talking between RNA Pol III and Pol II. The cross-talking is initiated by BRF, magnified by the mutation of FES1A, and finally has an effect on thermotolerance.
Highlights
Our results show that the abundance of BRF2 in fes1a mutants was correlated with the sensitivity of fes1a mutants to heat stress, further suggesting that BRF2 is a negative regulator of thermotolerance defect in fes1a
According to the different expressions of heat shock proteins (HSPs) at the recovery stage, we further evaluated the transcriptional activity of RNA Pol II in fes1a-1 and fes1a-3 by examining the phosphorylation of the Cterminal domain (CTD) of RNA Polymerase II largest subunit 1 (RPB1), using anti-S2P-CTD and anti-S5P-CTD antibodies
Using allelic hybridization (Supplemental Table 8) and evaluation of double mutants, we found that BRF2, a gene downstream of FES1A, is responsible for increasing the thermo-sensitivity of fes1a mutants
Summary
Thermotolerance in plants is associated with a number of regulatory and functional genes which constitute complex signaling pathways. It has been found that abscisic acid, salicylic acid, ethylene, reactive oxygen species, membrane fatty acid composition, ubiquitin, heat shock proteins (HSPs), programmed cell death, and photooxidation are all involved in thermotolerance. Out of numerous heat response-related factors, HSPs are the best understood. HSPs function as molecular chaperones to prevent cellular proteins from denaturation and to promote the refolding of damaged proteins. Different classes of HSPs function in different ways. HSP101 is mainly responsible for dispersing the aggregates of heat-denatured proteins (Merret et al, 2017). Cytosolic HSP90 regulates the heat shock response (Mclellan et al, 2007). Once HSP90 chaperon complex becomes inactivated, the Arabidopsis mutant shows a defect in thermotolerance (Fernández-Bautista et al, 2018). Apart from preventing the aggregation of denatured proteins and assisting the refolding of heat-denatured proteins
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