Transcriptional factors for stress signaling, oxidative protection, and protein modification in ipt-transgenic creeping bentgrass exposed to drought stress

Abstract

Overexpressing the cytokinin (CK)-synthesizing gene, isopentenyl transferase (ipt), is known to elevate endogenous CK levels and positively regulate drought tolerance. The objective of this study was to identify transcriptional factors (TFs) and their down-stream genes responsive to ipt overexpression which are associated with improved drought tolerance in creeping bentgrass (Agrostis stolonifera). Transcriptomic profiling was conducted in both the wild type (WT) (cv. ‘Penncross’) and ipt-transgenic creeping bentgrass exposed to well-watered condition and drought stress. A total of 65 TFs showed significantly increased and 62 TFs decreased expression levels in ipt-transgenic compared to the WT exposed to drought stress. The down-stream genes of 15 TFs were also differentially expressed between ipt-transgenic and WT plants. In addition, ipt-transgenic and WT exposed to drought stress also showed differential expression of genes for receptor kinases, stress defense, protein modification, and protein degradation. The transcriptomic analysis revealed that overexpressing ipt gene caused transcriptional changes with central hubs of bHLH148 and MYB4/4-like and WRKY28/53/71. Such TFs also showed to be associated with the up-regulation of transcripts that are involved in jasmonic acid signaling and down-regulation of abscisic acid signaling and antioxidant response, as well as efficient MAPKKK-mediated protein modification and RNA degradation. The changes in the aforementioned pathways could contribute to the transcriptional regulation of CK for improving drought tolerance in creeping bentgrass.