Transcription factor BES1 interacts with HSFA1 to promote heat stress resistance of plants

Abstract

Heat stress is a major environmental stress type that can limit plant growth and development. To survive sudden temperature increases, plants utilize the heat shock response, an ancient signaling pathway. Initial results had suggested a role for brassinosteroids (BRs) in this response. Brassinosteroids are growth-promoting steroid hormones whose activity is mediated by transcription factors of the BES1/BZR1 subfamily. Here, we provide evidence that BES1 can contribute to heat stress signaling. In response to heat, BES1 is activated even in the absence of BRs and directly binds to heat shock elements (HSEs), known binding sites of heat shock transcription factors (HSFs). HSFs of the HSFA1 type can interact with BES1 and facilitate its activity in HSE binding. These findings lead us to propose an extended model of the heat stress response in plants, in which the recruitment of BES1 is a means of heat stress signaling cross-talk with a central growth regulatory pathway.

A Brassinosteroids-BES1 Regulatory Module Manipulate Thermomemory in Arabidopsis thaliana

“…Studies in Arabidopsis and tomato demonstrate that downstream of BRs signaling, but not BRs level, make sense in heat stress response (Mazorra et al, 2011;Setsungnern et al, 2020). Similarly, a latest study reveals that BES1 is rapidly dephosphorylated and activated by heat stress in a manner independent of BRs signaling (Albertos et al, 2022). It seems like a paradox that BRs activate BES1/BZR1 but endogenous BRs levels are indispensable for thermal tolerance.…”

“…A recent study indicates that a defect in BES1 showed serious sensitive characteristics to heat stress compared to wild type. Heat shock rapidly activates BES1 and ABA promotes the dephosphorylation of BES1 through repressing the activity of PP2C-type phosphatases in HS process (Albertos et al, 2022). HSP90 forms a complex with BES1 and assists the compartmentalized cycle between active and inactive BES1 (Samakovli et al, 2020;Shigeta et al, 2015).…”

“…In tomato, epi-brassinolide (EBL) induces thermotolerance and peroxidase (POD) activity (Mazorra, Holton, Bishop, & Nunez, 2011). HS promotes the dephosphorylation of BES1 through repressing the activity of type 2C phosphatases (PP2Cs), activated BES1 directly binds to heat shock elements (HSEs) thus contribute to HS signaling (Albertos et al, 2022). These studies demonstrate that BRs signal play a positive role in HS response.…”

“…Given that BRs act positively in thermomemory, we then investigated whether the defect in BRs synthesis weakened memory response. Previous studies reported that BR-deficient and -overproduction seedlings represented similar thermal tolerance (Albertos et al, 2022;Mazorra et al, 2011), to further investigate whether endogenous BRs levels affect thermomemory, we subject 5-day-old det2 and DET2-OX seedlings to our priming and triggering stimulus protocol. Surprisingly, both det2 and DET2-OX represented enhanced thermal tolerance (Supplementary Fig.…”

“…HS activates BES1 via dephosphorylation (Albertos et al, 2022), so we are curious about whether the state can be sustained in the memory phase. We executed a transient expression experiment on N. benthamiana leaves to explore the subcellular distribution of BES1 after heat priming.…”