24-nt phasiRNAs move from tapetal to meiotic cells in maize anthers

Area of Science:

• Plant biology
• Molecular genetics
• RNA biology

Background:

• 24-nt phased, secondary small interfering RNAs (phasiRNAs) are abundant in maize meiotic anthers.
• Their precise distribution and functions within anther cell types remain largely unknown.

Purpose of the Study:

• To investigate the spatial and temporal distribution of 24-nt phasiRNA precursors and products in developing maize anthers.
• To determine the cell-specific origins and potential mobility of 24-nt phasiRNAs.

Main Methods:

• Laser capture microdissection to isolate specific anther cell types (tapetum, meiocytes, somatic cells).
• RNA and small RNA profiling to quantify transcript and small RNA levels.
• Single-molecule and small RNA fluorescence in situ hybridization (smFISH/sRNA-FISH) for spatial localization.

Main Results:

• The tapetum is identified as the primary production site for 24-PHAS precursor transcripts and Dcl5, yielding 24-nt phasiRNAs.
• 24-nt phasiRNAs are detected in all analyzed anther cell types, with highest accumulation in meiocytes, followed by tapetal cells.
• Evidence suggests 24-nt phasiRNAs are mobile, moving from the tapetum to meiocytes and other somatic cells.

Conclusions:

• The tapetum is the main source of 24-nt phasiRNAs in maize anthers.
• These phasiRNAs can move between cells, indicating intercellular communication.
• Potential roles for 24-nt phasiRNAs in regulating gene expression and development across different anther cell types are proposed.