Horizontally Transferred Salivary Protein Promotes Insect Feeding by Suppressing Ferredoxin-Mediated Plant Defenses.

Area of Science:

• Evolutionary Biology
• Molecular Biology
• Entomology

Background:

• Herbivorous insects secrete proteins to aid feeding, but the origin and evolution of these genes are unclear.
• Orphan salivary proteins in insects, like those in whiteflies, are crucial for plant-insect interactions.
• Understanding gene recruitment and evolution in plant-insect interactions is a significant knowledge gap.

Purpose of the Study:

• To investigate the origin and function of a horizontally transferred gene in the whitefly Bemisia tabaci.
• To elucidate the mechanism by which the insect salivary protein BtFTSP1 interacts with host plant proteins.
• To explore the evolutionary implications of horizontal gene transfer in mediating plant-insect interactions.

Main Methods:

• Identification and characterization of a horizontally transferred gene (BtFTSP1) from fungi to insects.
• Analysis of BtFTSP1's interaction with Nicotiana tabacum ferredoxin 1 (NtFD1) in planta.
• Gene silencing and overexpression experiments in Bemisia tabaci and Nicotiana tabacum.

Main Results:

• A horizontal gene transfer event from fungi to an Aleyrodidae insect ancestor ~42-190 million years ago introduced the BtFTSP1 gene.
• BtFTSP1 targets and degrades the plant defense protein NtFD1 via a ubiquitin-dependent pathway, facilitating insect feeding.
• Overexpression of BtFTSP1 benefits insects, while its silencing impairs feeding, demonstrating its crucial role.

Conclusions:

• Horizontally transferred genes play a significant role in the evolution of plant-insect interactions.
• The BtFTSP1-NtFD1 interaction is a novel adaptation evolved after gene transfer, absent in the fungal donor.
• This study provides insights into the origin of orphan salivary genes in insects through horizontal gene transfer.