Sub-cellular trafficking of phytochemicals explored using auto-fluorescent compounds in maize cells

Area of Science:

• Plant Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Plant cells' small molecule trafficking mechanisms are poorly understood.
• Phytochemical transport pathways may differ from protein transport routes.
• Novel trafficking pathways might have co-evolved with plant metabolic pathways.

Purpose of the Study:

• Investigate the sub-cellular localization and trafficking of auto-fluorescent compounds in maize.
• Determine if phytochemicals use distinct pathways for cell wall and vacuolar targeting.
• Utilize P1 transcription factor-induced compounds to study plant small molecule transport.

Main Methods:

• Maize BMS cells expressing an estradiol-inducible P1 transcription factor were used.
• Accumulation and sub-cellular localization of green and yellow fluorescent compounds were analyzed.
• Electron microscopy and BFA/monensin treatments were employed to study trafficking routes.

Main Results:

• Yellow fluorescent compounds accumulated in the vacuole within structures resembling anthocyanin-containing vesicles (AVIs).
• Green fluorescent compounds initially accumulated in the cytoplasm and were secreted to the cell wall via a Golgi-independent pathway.
• Electron-dense structures involved in green compound secretion were observed fusing with the plasma membrane.

Conclusions:

• Two distinct trafficking pathways exist in maize cells for compounds induced by the same transcription factor.
• Green auto-fluorescent compounds are secreted to the cell wall through a novel pathway, not involving the Trans-Golgi Network (TGN).
• Yellow auto-fluorescent compounds accumulate in the vacuole, providing insights into phenolic compound accumulation and potential for metabolic engineering.