ABSTRACT: Our previous studies have shown that exogenous ethylene (ETH) may induce plant adventitious root development in cucumber. In this study, transcriptome technique was used to explore the key genes in ETH-induced rooting. The results revealed that ETH regulated 1415 diferentially expressed genes (DEGs) during rooting, among which 687 DEGs were up-regulated and 728 DEGs were down-regulated. According to Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis, the critical pathways involved in ETH-induced adventitious root development were selected for further study, including carbon metabolism [starch and sucrose metabolism, glycolysis / gluconeogenesis, citrate cycle (TCA cycle), oxidative phosphorylation, fatty acid biosynthesis and fatty acid degradation], secondary metabolite biosynthesis (phenylalanine metabolism and flavonoid biosynthesis) and plant hormone signal transduction. In carbon metabolism, ETH reduced t the expression of CsHK2, CsPK2 and CsCYP86A1, whereas enhanced the expression of CsBAM1 and CsBAM3. Moreover, ETH negatively regulated the transcript level of CsPAL and CsF3’M and positively mediated that of CsPAO in secondary metabolite biosynthesis pathway. Additionally, ETH could induce adventitious rooting by negatively regulating auxin and ETH signal transduction-related genes (CsLAX5, CsGH3.17, CsSUAR50 and CsERS) and positively regulating ABA and BR signaling transduction-related genes (CsPYL1, CsPYL5, CsPYL8, CsBAK1 and CsXTH3) . Furthermore, the results of real-time PCR about the mRNA levels of these genes were consistent with transcriptome results. Therefore, ETH may induce adventitious root development by regulating carbon metabolism-related genes, secondary metabolite biosynthesis-related genes and plant hormone signal transduction-related genes.
