Multiple exposures to drought ‘train’transcriptional responses in Arabidopsis

摘要

Pre-exposure to stress may alter plants’ subsequent responses by producing faster and/orstronger reactions implying that plants exercise a form of ‘stress memory’. The mechanismsof plants’ stress memory responses are poorly understood leaving this fundamental biologicalquestion unanswered. Here we show that during recurring dehydration stresses Arabidopsisplants display transcriptional stress memory demonstrated by an increase in the rateof transcription and elevated transcript levels of a subset of the stress–response genes(trainable genes). During recovery (watered) states, trainable genes produce transcripts atbasal (preinduced) levels, but remain associated with atypically high H3K4me3 and ser5Ppolymerase II levels, indicating that RnA polymerase II is stalled. This is the first example ofa stalled RnA polymerase II and its involvement in transcriptional memory in plants. Thesenewly discovered phenomena might be a general feature of plant stress–response systems andcould lead to novel approaches for increasing the flexibility of a plant’s ability to respond to theenvironment.