Wheat Tae-MIR1118 Constitutes a Functional Module With Calmodulin TaCaM2-1 and MYB Member TaMYB44 to Modulate Plant...

Area of Science:

• Plant Molecular Biology
• Abiotic Stress Physiology
• Agricultural Science

Background:

• MicroRNAs (miRNAs) are crucial regulators of gene expression in plants, influencing responses to environmental stresses.
• Abiotic stresses, such as low nitrogen availability, significantly impact crop yield and require complex genetic regulation.
• Understanding specific miRNA-target interactions and downstream pathways is vital for improving crop resilience.

Purpose of the Study:

• To characterize the functional module Tae-MIR1118/TaCaM2/TaMYB44 in Triticum aestivum (wheat) for mediating low-nitrogen (N) stress response.
• To elucidate the regulatory mechanism of Tae-MIR1118 on its target gene TaCaM2 and the interaction between TaCaM2 and TaMYB44.
• To investigate the role of this pathway in plant adaptation to low-N stress and its potential for yield improvement.

Main Methods:

• Dual luciferase assays to confirm post-transcriptional regulation of TaCaM2 by Tae-MIR1118.
• Gene expression analysis under varying N levels to observe transcript patterns.
• Yeast two-hybrid, BiFC, and Co-IP assays to verify protein-protein interactions.
• Transgene analysis and gene knockdown to assess functional roles in stress adaptation.
• Yeast one-hybrid, ChIP-PCR, and transcriptional activation assays to identify TaMYB44 targets.

Main Results:

• Tae-MIR1118 directly targets and represses TaCaM2 expression via post-transcriptional cleavage.
• TaCaM2 interacts with the MYB transcription factor TaMYB44.
• The Tae-MIR1118/TaCaM2/TaMYB44 pathway negatively regulates Tae-MIR1118 and positively regulates TaCaM2 and TaMYB44 to enhance low-N stress adaptation.
• TaMYB44 directly binds to promoters of TaGS2.2, TaNRT2.1, and TaPIN4, inducing their transcription.
• A major haplotype, TaMIR1118-Hap1, confers enhanced low-N stress tolerance in wheat.

Conclusions:

• The Tae-MIR1118/TaCaM2/TaMYB44 pathway is a key regulator of the low-nitrogen response in wheat.
• This pathway modulates glutamine synthetase activity, nitrogen uptake, and root morphology for improved stress adaptation.
• The identified pathway and specific haplotypes offer potential targets for breeding wheat varieties with enhanced nitrogen use efficiency and stress tolerance.