Plants, able to meet their energy needs from the light of the sun, have organized their molecular activities around the recurring availability of light every day. Almost all aspects of a plant’s physiology and metabolism are orchestrated to precise times in the daily cycle. This daily fluctuation in metabolism impacts plant interactions with the environment including biotic and abiotic stress responses. The results of any -omic analysis and subsequent interpretations of the plant responses to given environmental stimuli are significantly affected by the time of day that the experiment is performed.<br/>We explored the effects of time of day on the plant transcriptional and metabolic responses to heat stress. We observed both qualitative and quantitative differences in the response to the exact same stimuli depending on the time of day the experiment was performed. Transcript levels, even of classical heat responsive transcripts, showed significant variation between plants exposed to the same temperature stress at different times of the day. As expected, since a majority of the plant transcriptome shows a rhythmic expression throughout the day, some observed variation in responses that could be attributed to altered transcript levels before the stress was applied. However, some transcripts showed unique responses at only one time of day, even when starting at the same pre-stress level. We used this temporal variation, employing time as a perturbagen and interrogated network connectivity and regulatory relationships in the transcriptional networks responding to heat at different times of the day. We identified previously uncharacterized heat responses and network connections. Our results suggest that time of day is a critical experimental factor and that our bias as a diurnally active observer may influence our understanding of plant responses not only to heat but to all environmental stresses.

Temporal-omics, incorporating time into high-throughput plant-omics

255th National Meeting (2018)

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