Odorant-Binding Proteins OBP57d and OBP57e Affect Taste Perception and Host-Plant Preference in Drosophila sechellia

Takashi Matsuo,Shigeru Sugaya,Toshiro Aigaki,Jyunichiro Yasukawa,Yoshiaki Fuyama,Mohamed A F Noor

doi:10.1371/journal.pbio.0050118

Abstract

Despite its morphological similarity to the other species in the Drosophila melanogaster species complex, D. sechellia has evolved distinct physiological and behavioral adaptations to its host plant Morinda citrifolia, commonly known as Tahitian Noni. The odor of the ripe fruit of M. citrifolia originates from hexanoic and octanoic acid. D. sechellia is attracted to these two fatty acids, whereas the other species in the complex are repelled. Here, using interspecies hybrids between D. melanogaster deficiency mutants and D. sechellia, we showed that the Odorant-binding protein 57e (Obp57e) gene is involved in the behavioral difference between the species. D. melanogaster knock-out flies for Obp57e and Obp57d showed altered behavioral responses to hexanoic acid and octanoic acid. Furthermore, the introduction of Obp57d and Obp57e from D. simulans and D. sechellia shifted the oviposition site preference of D. melanogaster Obp57d/eKO flies to that of the original species, confirming the contribution of these genes to D. sechellia's specialization to M. citrifolia. Our finding of the genes involved in host-plant determination may lead to further understanding of mechanisms underlying taste perception, evolution of plant–herbivore interactions, and speciation.

Highlights

Every animal must locate and identify sufficient food to meet its biological requirements
By comparing D. melanogaster and D. sechellia, we revealed that two genes encoding odorantbinding proteins, Obp57d and Odorant-binding protein 57e (Obp57e), are involved in the fruit fly’s taste perception, but can change the behavioral response of the flies to the toxins contained in the fruit
We previously reported that the behavioral difference between D. sechellia and D. simulans in response to hexanoic acid (HA), one of the main components of odor from the ripe fruit of M. citrifolia, is controlled by at least one gene on the second chromosome [17]

Summary

Introduction

Every animal must locate and identify sufficient food to meet its biological requirements. If an insect species acquires resistance to a plant toxin, it may reap an ecological advantage by gaining exclusive access to the toxic plant and may subsequently evolve as a specialist herbivore with a specific preference towards that plant. Such physiological and behavioral specialization plays an important role in the evolution of divergent ecological interactions between herbivores and their host plants. Genomic fragments including Obp57d/e were PCR cloned from D. simulans and D. sechellia with the primers P1 and P2, and cloned into the pCaSpeR3 transformation vector. Either of a primer pair was designed at an exon boundary to ensure amplification only from spliced transcripts

Methods

Results

Conclusion