Plant development is strikingly flexible with respect to the environment. Among the various external cues that plants monitor to optimize their fitness, temperature is critical even within the limits that are not considered as a stress factor (ie, between 12 and 28ºC for Arabidopsis thaliana), and its effects on plant development are collectively known as 'thermomorphogenesis'. The molecular mechanisms that allow the perception of temperature and the signaling events that ultimately regulate gene expression have been well studied over the past 15 years, and a robust gene regulatory network (GRN) has been defined in which at least one photoreceptor also acts as a thermosensor, and several transcription factors that regulate the response to light, also regulate the response to temperature.

However, some long-standing observations indicate that important questions remain unsolved. For instance, temperature changes are more dramatic above ground, but roots can also respond to temperature. Then, to which extent is temperature perceived autonomously by different organs, tissues or cell types? Is there a central hub that transduces temperature information to different parts of the plant? What are the organ-, or tissue- or cell type-specific regulatory circuits through which temperature signals operate? What molecular and physiological mechanisms are set in place at different temperatures, so that optimal fitness is achieved at all temperatures?

In this project, we propose to study the spatial regulation of temperature signaling from different angles. Our pilot transcriptomic experiment has identified large sets of genes that are differentially expressed in shoots vs roots of plants growing permanently in different temperatures, and also as a short-term response to temperature changes. Preliminary analysis of these data suggests that there are different GRNs operating in roots and shoots. In WP1 we propose to define these organ-specific GRNs and experimentally validate their relevance in the different organs. Using an experimental system developed by our collaborators at CBGP (Madrid), in WP2 we will explore the behavior of roots of plants in which only the aerial part is subject to different temperatures, also analyzing the potential mechanisms by which above-ground temperature changes are communicated to below-ground organs -the roots. To explore if there are also cell-type specific GRNs for temperature regulation, in WP3 we propose to perform scRNAseq experiments of leaves of plants growing at different temperatures. Finally, in WP4 we will focus on the under-studied connection between temperature, the plant's metabolic status, and hypoxia, in roots and shoots, using preliminary information extracted from our pilot transcriptomic analysis.