Genome-wide transcriptomic profiles reveal multiple regulatory responses of poplar to Lonsdalea quercina infection

Remarkable gene expression changes and responsive DEGs were found in poplar upon pathogen attack and provide important clues to the molecular mechanism of defense responses in plants and gene functional studies of trees. The disease Lonsdalea canker affects the growth and productivity of poplar (Populus spp.), often resulting in death of poplar trees. To obtain expression profiles of differentially expressed genes (DEGs) for the response of poplar to pathogens, transcriptomic sequencing was performed using bark from 2-year-old P. x euramericana Guinier trees inoculated (IN) or mock-inoculated (KK) with Lonsdalea quercina. In total, 7,558,430 and 7,149,345 clean reads were generated in the KK and IN libraries, respectively. Gene expression profiles identified a total of 7098 DEGs, among which there were nearly twice as many down-regulated (4635) as up-regulated (2463) genes post-inoculation. Expression was further validated and dynamic responses analyzed by qRT-PCR. These DEGs were predominantly related to the biosynthesis of secondary metabolites, plant hormone signal transduction, regulation of autophagy, and ABC transport upon L. quercina infection. In addition, DEGs involved in the flavonoid biosynthesis pathway, and JA and SA-mediated signal transduction pathways might play important roles in the L. quercina infection response in P. x euramericana. The pathogen-responsive DEGs identified in this investigation provide important clues to the molecular mechanism of defense responses in plants and gene functional studies of trees.