Analyses of microRNA166 gene structure, expression, and function during the early stage of somatic embryogenesis in...

Area of Science:

• Plant Molecular Biology
• Developmental Biology
• Genetics

Background:

• MicroRNA166 (miR166) is crucial for post-transcriptional gene regulation, impacting plant growth and development by targeting HD-ZIP III family genes.
• The specific roles, expression patterns, and structural features of miR166 during early somatic embryogenesis in Dimocarpus longan (longan) are not well understood.

Purpose of the Study:

• To characterize the structural properties, expression profiles, and functional roles of miR166 genes during early somatic embryogenesis in Dimocarpus longan.
• To investigate the regulatory mechanisms of miR166 in response to plant hormones and its relationship with the target gene ATHB15.

Main Methods:

• Isolation and characterization of pri-miR166 and pre-miR166 transcripts, including identification of transcription initiation sites (TSSs) and potential small open reading frames (smORFs).
• Analysis of promoter regions for cis-acting elements responsive to various stimuli.
• Quantitative analysis of pre-miR166 and ATHB15 expression levels under different hormonal treatments (2,4-D, abscisic acid, ethylene) and during distinct developmental stages (callus to globular embryo).
• Experimental manipulation using miR166a.2-agomir, miR166a.2-antagomir, and miPEP166 S338 to assess their effects on miR166a.2 and ATHB15 expression.

Main Results:

• Two pri-miR166 transcripts (S78 and S338) with distinct TSSs and potential miPEP encoding regions were identified. Promoter analysis revealed responsiveness to diverse stimuli.
• Pre-miR166 S78 and S338 expression increased upon treatment with 2,4-D, abscisic acid, and ethylene, with pre-miR166 S338 showing a stronger response, indicating complex transcriptional and maturation regulation.
• A negative correlation was observed between pre-miR166 and ATHB15 expression during somatic embryogenesis progression, suggesting a feedback mechanism. Exogenous application of agomir, antagomir, and miPEP modulated these expressions without consistent linear synchronization.

Conclusions:

• MiR166 transcription and maturation are complex and not strictly linearly correlated with hormonal stimuli during longan somatic embryogenesis.
• A negative regulatory feedback loop exists between miR166 and its target gene ATHB15 during early longan somatic embryogenesis.
• The study provides insights into the intricate regulation of miR166 and its potential role in controlling developmental transitions in longan, highlighting the complexity of miRNA-mediated gene silencing.