Transcriptomic Profiling for Drought-Responsive Genes Regulated By Cytokinins in Transgenic Creeping Bentgrass.

Transgenic creeping bentgrass (Agrostis stolonifera) overexpressing adenine isopentenyltransferase gene (ipt) driven by a senescence-activated promoter (SAG12) exhibit improved drought tolerance. The objective of this study was to determine drought-responsive transcriptional factors and genes regulated by increased endogenous cytokinin production in the transgenic creeping bentgrass that contribute to the improved drought tolerance. Both wild-type (‘Penncross’) and transgenic (‘S41’) plants were exposed to 21 days of drought stress in growth chamber. Global gene expression analysis conducted by Illumina platform-based RNA-seq for both ‘WT’ and ‘S41’ leaf tissues found 661 and 648 up-regulated genes, 764 and 862 down-regulated genes under drought stress conditions compared with their respective controls with fold change ≥ 4 at P level ≤ 0.001. Among them, 474 up-regulated genes and 598 down-regulated genes were shared between ‘WT’ and ‘S41’. Gene ontology and pathway analysis showed that an increase of gene regulation in photorespiration, TCA cycle, antioxidant capacity, and transcription factors related to stress tolerance was found in ‘S41’ leaf, compared with ‘WT’. The transcript abundances of genes related other phytohormones, such as auxin, abscisic acid, brassinosteroid, ethylene, gibberellic acid, were also more up-regulated or less down-regulated in ‘S41’ than ‘WT’. The transcriptomic data in this study revealed the mechanistic relationship between endogenous cytokinin manipulation and drought tolerance in creeping bentgrass, and thus may serve as a guide for future molecular breeding of drought-resistant cultivars.