Integration of mRNA-miRNA revealed the possible role of PyCYCD3 may increasing branches through bud-notching in pear (Pyrus bretschneideri Rehd)

Abstract

Background: The initiation of branching from the main stem of a pear tree is hindered in the absence of external stimuli, resulting in poor quality branching. Endogenous hormones and associated genes are pivotal in regulating the branching process in pear trees, while the patterns of branching in fruit trees and the underlying chemical mechanisms remain enigmatic. Methods: The impact of notching on 'Huang guan' pear buds was investigated through the assessment of germination rate, branching rate, and hormone levels. Transcriptome sequencing was employed to examine mRNA and miRNA expression in notched and control buds, leading to the identification of a mRNA-miRNA network, which was subsequently validated using qRT-PCR. Furthermore, the CYCD3 gene was genetically manipulated and analyzed in notched and control buds of pears. Results: Based on KEGG analysis, a notable proportion of the differentially expressed genes (DEGs) are linked to the biosynthesis pathway of plant compounds involved in signal transduction within the organism. Within this subset of DEGs, PyCYCD3was identified as an up-regulated gene, potentially indicating its involvement in the regulation of branching processes. Furthermore, a comprehensive investigation identified fifteen miRNAs that target three genes associated with plant hormones. The differentially expressed genes (DEGs) were validated through quantitative real-time polymerase chain reaction (qRT-PCR). PyCYCD3was chosen for transformation into wild Arabidopsis plants, resulting in the generation of transgenic Arabidopsis plants. Subsequent analysis of branching patterns, plant hormone levels, and relative gene expression suggests that PyCYCD3may play a significant role in promoting lateral branches in pear trees through bud-notching. Conclusions: This study suggests that the transport of brassinosteroids from lateral branches to the stem in pear trees may be crucial for the development of lateral buds. PyCYCD3 likely plays a significant regulatory role in both bud germination and branch growth.