Study : Immediate transcriptional responses to heat shock of plant leaf


Immediate transcriptional responses to heat shock of plant leaf
Ambient temperature is one of the most important environment factors that direct all organisms for morphogenesis, metabolisms and growth. Plants have evolved efficient mechanisms adapting temperature fluctuation such as heat stress response (HSR). Although transcriptional regulatory network of plant HSR has been established, little is known on the genome-wide transcriptional changes within first several minutes upon heat shock (HS). To precisely measure the very first wave of transcriptional response to HS, we investigated the nascent RNA and mature mRNA from plant leaf tissue exposure to 5-min HS treatment using global run-on sequencing (GRO-seq) and RNA sequencing (RNA-seq) methods. We found that only a small group of genes were both up- or down-regulated at nascent RNA and mRNA levels. Primed plants that already exposed to a mild heat stress induced a more drastic transcriptomic alteration than naïve plants which had not experienced a heat stress. Group A1 HEAT SHOCK TRANSCRIPTION FACTORs (HsfA1s) are the major transcription factors in charge of the very early transcriptional HSR. Within 5-minute HS, we also observed that: 1) Engaged RNA polymerase II (Pol II) was accumulated downstream of transcription start sites; 2) 5 pause-release is a rate limiting step for induction of some heat shock protein genes; 3) A good number of genes switched transcription modes; 4) Pervasive read-through was induced at terminators. Plants HSR is transcriptionally very quick. GRO-seq is sensitive and robust to detect quick response to HS. Heat stress memory takes place at multiple steps of transcription cycles such as Pol II recruitment, 5 pausing, elongation and termination. Overall design: Transcriptional profiling by GRO-seq and RNA-seq


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