tasiR-ARFs Production and Target Regulation during In Vitro Maize Plant Regeneration

Area of Science:

• Plant Biology
• Molecular Biology
• Genetics

Background:

• Plant regeneration in vitro requires somatic cells to dedifferentiate into pluripotent cells.
• Auxins are crucial for this cellular plasticity, mediating their effects through auxin response factors (ARFs).
• Small trans-acting siRNAs (ta-siRNAs), specifically tasiR-ARFs derived from TAS3 transcripts, regulate ARF activity.

Purpose of the Study:

• To investigate the role of TAS3-derived tasiRNAs in maize in vitro plant regeneration.
• To understand the dynamic expression patterns of TAS3, miR390, tasiR-ARFs, and their targets during regeneration.
• To elucidate the regulatory mechanisms of tasiR-ARFs in controlling cell fate plasticity.

Main Methods:

• Quantitative analysis of TAS3, miR390, tasiR-ARF, ARF, AGO7, and LBL1 transcript levels in embryogenic callus (EC) and non-embryogenic callus (NEC).
• Hormonal treatments (half-reduction, depletion) and photoperiod changes to induce regeneration.
• Microscopic observation of auxin accumulation patterns.

Main Results:

• TAS3b and its derived tasiR-ARFs were less abundant in NEC, while TAS3g, miR390, and tasiR-ARFg were more abundant.
• AGO7 and LBL1, key for tasiR-ARF biogenesis, were higher in EC, suggesting limited tasiR-ARF production in NEC.
• Regeneration initiation correlated with increased TAS3g, miR390, and tasiR-ARFg, followed by TAS3b and tasiR-ARF accumulation upon hormone depletion.

Conclusions:

• tasiR-ARFs play a dynamic, regulatory role throughout maize in vitro regeneration.
• The balance between different TAS3 transcripts and their derived tasiRNAs is critical for controlling ARF activity and cell fate.
• This study reveals a novel layer of post-transcriptional gene regulation governing plant regeneration.