Epigenetic regulation of thermomorphogenesis and heat stress tolerance

Abstract

Many environmental conditions fluctuate and organisms need to respond effectively. This is especially true for temperature cues that can change in minutes to seasons and often follow a diurnal rhythm. Plants cannot migrate and most cannot regulate their temperature. Therefore, a broad array of responses have evolved to deal with temperature cues from freezing to heat stress. A particular response to mildly elevated temperatures is called thermomorphogenesis, a suite of morphological adaptations that includes thermonasty, formation of thin leaves and elongation growth of petioles and hypocotyl. Thermomorphogenesis allows for optimal performance in suboptimal temperature conditions by enhancing the cooling capacity. When temperatures rise further, heat stress tolerance mechanisms can be induced that enable the plant to survive the stressful temperature, which typically comprises cellular protection mechanisms and memory thereof. Induction of thermomorphogenesis, heat stress tolerance and stress memory depend on gene expression regulation, governed by diverse epigenetic processes. In this Tansley review we update on the current knowledge of epigenetic regulation of heat stress tolerance and elevated temperature signalling and response, with a focus on thermomorphogenesis regulation and heat stress memory. In particular we highlight the emerging role of H3K4 methylation marks in diverse temperature signalling pathways.

PIF4 Promotes Expression of HSFA2 to Enhance Basal Thermotolerance in Arabidopsis

“…Previous studies have well established that PIF4 is a core hub of thermomorphogenesis and photomorphogenesis in plants [ 6 , 55 ]. In darkness, PIF4 promotes skotomorphogenic development, thereby leading to rapid hypocotyl elongation [ 56 ].…”

“…In recent years, global warming has caused frequent occurrences of extreme weather, which have had a detrimental impact on plant growth and development throughout the whole plant life cycle [ 64 ]. As sessile organisms, plants cannot migrate to avoid extreme temperatures; therefore, multiple strategies have evolved to sense and cope with heat stress in plants [ 6 , 8 , 21 ]. In general, extreme temperatures display two forms: high ambient temperatures (27~29 °C) and heat stress (≥30 °C) [ 5 , 6 ].…”

“…In general, the response of plants to temperature can be divided into two forms: acclimation and the tolerance response [ 5 , 6 ]. The definitions of warm temperatures and heat stress (HS) depend on the natural living conditions of specific species [ 5 ].…”

“…The definitions of warm temperatures and heat stress (HS) depend on the natural living conditions of specific species [ 5 ]. The optimum temperature for Arabidopsis is 20–22 °C, with 27–29 °C being considered to be a high ambient temperature [ 6 ]. Sessile plants can change their architecture in response to high ambient temperatures (27–29 °C) through elongated hypocotyls and petioles, thinned leaves, and hyponastic growth and early flowering, and these developmental processes have been collectively named thermomorphogenesis [ 7 , 8 , 9 ].…”

Chromatin-Based Transcriptional Reprogramming in Plants under Abiotic Stresses

“…The main pathway of epigenetic regulation to combat stresses such as heat involves DNA methylation, ATP dependent chromatin remodeling, histone modifications, long non-coding RNAs etc. [ 26 , 27 , 28 , 29 ]. All the above epigenetic modifications fine-tune the gene expression of heat-responsive genes to handle stress deftly [ 27 ].…”