Caragana korshinskii phenylalanine ammonialyase is up-regulated in the phenylpropanoid biosynthesis pathway in response to drought stress

Drought is one of the most severe abiotic stresses, the damage due to which, various plant species mitigate by activating mechanisms that are not yet well understood. Caragana korshinskii is a xerophytic shrub found in the semi-arid regions of northwest China with high tolerance to several abiotic stresses, including drought. Based on the de novo transcriptome data from C. korshinskii leaflets collected along a precipitation gradient on the Loess Plateau (China), most of the differentially expressed genes were explored using trend analysis along the precipitation gradient. Gene ontological analysis showed that “phenylpropanoid biosynthesis process → secondary metabolite biosynthetic process” terms were the most significant gene ontologies, whereas Kyoto Encyclopedia of Genes and Genomes-based analysis indicated that the biosynthesis of secondary metabolites was a significant metabolic pathway. Real-time polymerase chain reaction and enzyme activity analyses confirmed the increased transcription of the phenylalanine ammonialyase (PAL) gene in C. korshinskii under drought stress in field and laboratory conditions. These results suggested that C. korshinskii adjusts its secondary metabolism to water-deficit environments and activates PAL by drought stress. Therefore, further studies on the obtained data can expand the current understanding of the molecular and genetic mechanisms responsible for the drought endurance in C. korshinskii.