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Environmental stresses disturb the endoplasmic reticulum (ER) protein folding. However, primary metabolic responses induced by ER stress remain unclear. Thus, we investigated the morphophysiological and metabolomic changes under ER stress, induced by dithiothreitol (DTT) and tunicamycin (TM) treatments in sorghum seedlings from 24 to 96 h. The ER stress caused lipid peroxidation and increased the expression of SbBiP1, SbPDI, and SbIRE1. The development impairment was more pronounced in roots than in shoots as distinct metabolomic profiles were observed. DTT decreased root length, lateral roots, and root hair, while TM decreased mainly the root length. At 24 h, under ER stresses, the glutamic acid and o-acetyl-serine were biomarkers in the shoots. While homoserine, pyroglutamic acid, and phosphoric acid were candidates for roots. At the latest time (96 h), kestose and galactinol were key metabolites for shoots under DTT and TM, respectively. In roots, palatinose, trehalose, and alanine were common markers for DTT and TM late exposure. The accumulation of sugars such as arabinose and kestose occurred mainly in roots in the presence of DTT at a later time, which also inhibited glycolysis and the tricarboxylic acid cycle (TCA). Amino acid metabolism was induced, which also contributed TCA components decreasing, such as succinate in shoots and citrate in roots. Thus, our study may provide new insights into primary metabolism modulated by ER stress and seedling development., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Plants have developed mechanisms to avoid harmful effects of Na + accumulation, such as the signaling pathway of carrier proteins Na + /H + (NHX) and salt overly sensitive (SOS). Besides, endoplasmic reticulum (ER) could integrate plant cell response. Thus, we aimed to understand the effects of ER homeostasis impairment, and its relationship to salt stress during early stages of the Sorghum bicolor CSF 20 a salt-tolerant variety. Three days old seedlings were challenged with NaCl (0, 50, 75 and 100 mM), dithiothreitol (DTT) at 0, 2.5, 5.0 10.0 mM, and the combined NaCl and DTT treatments. Tunicamycin (TUN) was also used as a second inducer of ER stress in a quantitative PCR, to corroborate with DTT's results. There was no significant change in growth parameters under NaCl treatments. Nevertheless, seedling length, mass and Na + content were decreased as DTT concentration was increased. Under combined NaCl and DTT treatments, shoot length and fresh and dry masses were maintained at control levels. On the other hand, the levels of Na + were decreased, in comparison to NaCl treatment. Genes analyzed by qPCR revealed that NaCl was able to induce all of them, except for SbbZIP60, however it was induced under combined stresses. In conclusion, the results indicated that S. bicolor seedlings of CSF 20 variety were tolerant to salt and sensible to ER stress. The combination of both stresses restored the ER homeostasis promoting a decrease of Na + content via the membrane transporters SbNHX1, SbSOS1, and SbPDI ER-chaperone and the ER sensor SbbZIP60., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)