Characterizing serotonin biosynthesis in Setaria viridis leaves and its effect on aphids

Area of Science:

• Plant science
• Molecular biology
• Biochemistry

Background:

• Setaria viridis (green foxtail) is a model C4 plant and wild ancestor of foxtail millet.
• Molecular mechanisms of insect resistance in Setaria are not well understood.
• Aphid infestation is a significant agricultural challenge.

Purpose of the Study:

• To investigate the role of serotonin biosynthesis in Setaria viridis's defense against aphids.
• To identify genes involved in serotonin production in Setaria.
• To explore the potential of serotonin for developing pest-tolerant crops.

Main Methods:

• Metabolic analysis of Setaria viridis leaves under aphid infestation.
• Transcriptome analysis to identify key biosynthetic genes.
• Ectopic expression and gene silencing (virus-induced gene silencing) to validate gene function.
• Aphid bioassays with exogenous serotonin application and artificial diets.

Main Results:

• Setaria viridis accumulates tryptamine and serotonin in response to aphid infestation.
• Exogenous serotonin application and artificial diet bioassays increased aphid mortality.
• Key genes encoding tryptophan decarboxylase (TDC) and tryptamine 5-hydroxylase (T5H) were identified.
• Ectopic expression confirmed the enzymatic activities of SvTDC1 and SvT5H1.
• Gene silencing of SvTDC1 reduced serotonin levels in Setaria italica.

Conclusions:

• This study provides the first evidence of serotonin biosynthesis in Setaria leaves.
• Serotonin plays a role in plant defense against aphids.
• The identified genes and pathway are valuable for engineering pest resistance in Setaria italica.