Transcriptome analysis reveals the effects of strigolactone on shoot regeneration of apple.

KEY MESSAGE: We have demonstrated that strigolactone inhibitor, Tis108, could be used to improve shoot regeneration of apple, and provided insights into the molecular mechanism of strigolactone-mediated inhibition of adventitious shoot formation. Lack of an efficient transformation system largely stagnated the application of transgenic and CRISPR technology in apple rootstock. High shoot regeneration ability is an important basis for establishing an effective transformation system. In this study, we first demonstrated the inhibitory effects of strigolactones on the adventitious shoot formation of apple rootstock M26. Next, we successfully verified that strigolactone-biosynthesis inhibitor, Tis108, could be used to improve the shoot regeneration of woody plants. Our results also suggest strigolactone-biosynthesis gene, MdCCD7, can be a target gene for biotechnological improvements of shoot regeneration capacity. Furthermore, we have employed transcriptome analysis to reveal the molecular mechanism of strigolactone-mediated inhibition of adventitious shoot formation. Differentially expressed genes associated with photosynthesis, secondary growth, and organ development were identified. WGCNA suggests SLs might affect shoot regeneration through interaction with other hormones, especially, auxin, cytokinin, and ethylene. We were able to identify important candidate genes mediating the cross-talk between strigolactone and other hormones during the process of adventitious shoot formation. Overall, our findings not only propose a useful chemical for improving shoot regeneration in practice but also provide insights into the molecular mechanism of strigolactone-mediated inhibition of adventitious shoot formation.