Metabolomic and transcriptomic analysis of roots of tobacco varieties resistant and susceptible to bacterial wilt

Ralstonia solanacearum severely damages the growth of tobacco ( Nicotiana tabacum L.) and causes great economic losses in tobacco production. To investigate the root metabolism and transcriptional characteristics of tobacco bacterial wilt susceptible variety Cuibi-1 (CB-1) and resistant new line KCB-1 (derived from an ethyl methanesulfonate (EMS) mutant of CB-1) after infestation with R. solanacearum , root metabolism and transcriptional characteristics were investigated using RNA-Seq and liquid chromatography-mass spectrometry (LC-MS). Differences in resistance between KCB-1 and CB-1 were observed in several aspects: (1) The phenylpropanoid pathway was the main pathway of resistance to bacterial wilt in KCB-1 compared with CB-1. (2) KCB-1 had more differential metabolic markers of disease resistance than CB-1 after infection with R. solanacearum . Among them, the differential coumarin-like metabolites that affect quorum sensing (QS) and biofilm formation of R. solanacearum differ in KCB-1 and CB-1. (3) KCB-1 inhibited production of the R. solanacearum metabolite putrescine, and the level of putrescine in tobacco was positively correlated with susceptibility. (4) Compared with CB-1, the metabolites of KCB-1 had less differential nitrogen sources during the infestation of R. solanacearum , which was detrimental to the growth and reproduction of R. solanacearum . (5) Both indole-3-acetic acid (IAA) and abscisic acid (ABA) in CB-1 and KCB-1 were involved in the response to R. solanacearum infestation, but the levels of IAA and ABA in KCB-1 were greater than in CB-1 at 24 h post inoculation (hpi). In conclusion, R. solanacearum caused reprogramming of both root metabolism and transcription in KCB-1 and CB-1, and the transcriptional and metabolic characteristics of resistant tobacco were more unfavorable to R. solanacearum . • In this study, the transcriptomes and metabolomes of the roots of bacterial wilt susceptible tobacco Cuibi-1 (CB-1) and the new resistant strain KCB-1 were systematically studied before and after R. solanacearum infestation. Several important conclusions were drawn from the study, as follows: (1) The phenylpropanoid pathway was the main pathway of resistance to bacterial wilt in KCB-1 compared with CB-1 (2) KCB-1 had more and less disease-resistant differential metabolites and nitrogen sources after infection with R. solanacearum than CB-1. In addition, at 24 hpi, KCB-1 had higher levels of both IAA and ABA than CB-1. (3) KCB-1 inhibited production of the R. solanacearum metabolite putrescine, and the level of putrescine in tobacco was positively correlated with susceptibility.