Abscisic Acid: A Potential Secreted Effector Synthesized by Phytophagous Insects for Host-Plant Manipulation.

Area of Science:

• Plant biology
• Insect biology
• Biochemistry

Background:

• Abscisic acid (ABA) is a crucial plant signaling molecule regulating growth, development, and stress responses.
• ABA has been detected in various animals, including insects and humans.
• Phytophagous insects are known to interact with host plants, sometimes inducing galls.

Purpose of the Study:

• To investigate the presence and concentration of ABA in phytophagous insects.
• To determine if ABA levels differ between gall-inducing and non-gall-inducing insects.
• To explore the potential role of insect-derived ABA in plant manipulation.

Main Methods:

• High-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) was used to quantify ABA in 17 insect species.
• Immunohistochemistry was employed to localize ABA within insect tissues, specifically in the salivary glands of *Eurosta solidaginis* larvae.

Main Results:

• ABA was detected in all six insect orders examined, encompassing both gall-inducing and non-gall-inducing species.
• Insect ABA concentrations frequently exceeded those found in plants, suggesting endogenous synthesis.
• ABA was localized to the salivary glands of gall-inducing *Eurosta solidaginis* larvae.

Conclusions:

• Insects likely synthesize and secrete ABA, evidenced by high concentrations and localization in salivary glands.
• Insect-derived ABA may be used to manipulate host plant nutrient allocation and defense mechanisms.
• ABA, alongside cytokinins (CKs) and indole-3-acetic acid (IAA), represents a class of insect-manipulating phytohormones secreted from glandular organs.