Type-B cytokinin response regulators link hormonal stimuli and molecular responses during the transition from endo- to ecodormancy in apple buds

• Published in: Plant cell reports 2020-12, Vol.39 (12), p.1687-1703
• Main Authors: Cattani, Amanda Malvessi, da Silveira Falavigna, Vítor, Silveira, Carolina Pereira, Buffon, Vanessa, dos Santos Maraschin, Felipe, Pasquali, Giancarlo, Revers, Luís Fernando
• Format: Article
• Language: English
• Subjects: Apples; Arabidopsis - genetics; Biomedical and Life Sciences; Biotechnology; Buds; Cell Biology; Controlled conditions; Cytokinins; Cytokinins - pharmacology; Cytokinins - physiology; Developmental stages; Dormancy; Fruits; Gene expression; Gene Expression Regulation, Plant; Genes; Genomes; Life Sciences; Malus - drug effects; Malus - growth & development; Malus - physiology; Original Article; Phylogeny; Plant Biochemistry; Plant Dormancy - drug effects; Plant Dormancy - physiology; Plant Growth Regulators - metabolism; Plant Growth Regulators - pharmacology; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Sciences; Plants, Genetically Modified; Reporter gene; Signal transduction; Stimuli; Transcription factors
• ISSN: 0721-7714; 1432-203X
• DOI: 10.1007/s00299-020-02595-z

Key Message Cytokinin together with MdoBRR1 , MdoBRR8 and MdoBRR10 genes participate in the downregulation of MdoDAM1 , contributing to the transition from endo- to ecodormancy in apple buds. The final step of cytokinin (CK) signaling pathway culminates in the activation of type-B response regulators (BRRs), important transcriptional factors in the modulation of CK-responsive genes. In this study, we performed a genome-wide analysis aiming to identify apple BRR family members and understand their involvement in bud dormancy control. The investigation identified ten MdoBRR protein - coding genes. A higher expression of three MdoBRR ( MdoBRR1 , MdoBRR9 and MdoBRR10 ) was observed in dormant buds in comparison to other developmental stages. Interestingly, in ecodormant buds these three MdoBRR genes were upregulated in a CK-dependent manner. Transcription profiles, determined during dormancy cycle under field and artificially controlled conditions, revealed that MdoBRR1 and MdoBRR8 played important roles in the transition from endo- to ecodormancy, probably mediated by endogenous CK stimuli. The expression of MdoBRR7 , MdoBRR9, and MdoBRR10 was induced in ecodormant buds exposed to warm temperatures, indicating a putative role in growth resumption after chilling requirement fulfillment. Contrasting expression patternsin vivo between MdoBRRs and MdoDAM1 , an essential dormancy establishment regulator, were observed during dormancy cycle and in CK-treated buds. Thereafter, in vivo transactivation assays showed that CK stimuli combined with transient overexpression of MdoBRR1 , MdoBRR8, and MdoBRR10 resulted in downregulation of the reporter gene gusA driven by the MdoDAM1 promoter. These pieces of evidences point to the integration of CK-triggered responses through MdoBRRs that are able to downregulate MdoDAM1 , contributing to dormancy release in apple.