Distinct transcriptional programs control polyethylene glycol (PEG)-induced drought stress responses in oat (Avena...

Oats (Avena sativa L.) are generally considered tolerant to unfavorable environmental conditions, although drought is known to impose yield losses. Several breeding programs worldwide aim at producing new oat genotypes tolerant to water deficit, but the molecular mechanisms underlying drought responses remain scarcely characterized. We investigated the growth and biomass production of 12 oat genotypes submitted to dehydration induced by PEG. Shoot elongation and biomass production were severely impaired by osmotic stress, whereas in roots growth and dry weight were mostly increased. To gain further insight into the responses, seedlings from 'URS Altiva' were subjected to osmotic stress for seven days, their growth and biomass performance investigated, and the transcriptome was determined for the shoots and roots of control and water-stressed plants. Distinct transcriptional programs were demonstrated to control dehydration responses in shoots and roots, agreeing with the phenotypic responses. Photosynthesis and chloroplast assembly pathways were negatively affected in the shoots, whereas in the roots the transcription of defense genes was mostly impaired. The salvage pathways induced by osmotic stress in oat shoots and roots were shared, consisting of water deprivation and abscisic acid-mediated pathways. Candidate genes and transcription factors regulating these pathways in response to dehydration were identified. Three modules of co-regulated genes were demonstrated to be correlated with biomass production in the shoots and roots and shoot elongation. This work contributes to the current understanding of the molecular mechanisms underlying the differential response of shoots and roots to dehydration and may provide tools to develop new tolerant cultivars.