Cytokinins Are Abundant and Widespread Among Insect Species

Area of Science:

• Plant Biology
• Insect Biochemistry
• Chemical Ecology

Background:

• Cytokinins (CKs) are primarily known as plant growth regulators.
• Phytopathogenic microbes and gall-inducing insects are suspected to produce CKs to manipulate host plants.
• The presence and role of CKs in non-gall-inducing insects remain largely unexplored.

Purpose of the Study:

• To investigate the presence and diversity of CKs in various phytophagous insect species.
• To determine if CK production is linked to gall induction or herbivory in general.
• To explore the potential role of insect-derived CKs in plant-insect interactions.

Main Methods:

• High-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-MS/MS) was used.
• CK concentrations were analyzed in 17 species of phytophagous insects across six insect orders.
• A wide range of CK analytes were quantified and identified.

Main Results:

• CKs were detected in all six insect orders surveyed, including non-gall-inducing species.
• 24 different CK analytes were identified, with isoprenoid forms of trans-zeatin (tZ) and isopentenyladenine (iP) being most abundant.
• Insect CK concentrations often exceeded those found in plants, suggesting endogenous synthesis.
• CKs were found in both gall-inducing and non-gall-inducing insects.

Conclusions:

• Phytophagous insects synthesize CKs, which play roles beyond gall induction, including nutrient allocation and defense modification.
• The tRNA-isopentenyltransferase (ipt) pathway is postulated for insect CK production, functioning differently than in plants.
• Insect-derived CKs are significant mediators of plant-insect interactions during herbivory.