GEPHE SUMMARY Print
Gephebase Gene
Entry Status
Published
GepheID
GP00001781
Main curator
Courtier
PHENOTYPIC CHANGE
Trait Category
Trait State in Taxon A
D. simulans and D. mauritiana - presence of lamellocytes and ability to melanotically encapsulate parasitoids
Trait State in Taxon B
D. sechellia - no lamellocytes and inability to melanotically encapsulate parasitoids
Ancestral State
Taxon A
Taxonomic Status
Taxon A #1
Common Name
-
Synonyms
-
Rank
species
Lineage
Show more ... Brachycera; Muscomorpha; Eremoneura; Cyclorrhapha; Schizophora; Acalyptratae; Ephydroidea; Drosophilidae; Drosophilinae; Drosophilini; Drosophila; Sophophora; melanogaster group; melanogaster subgroup
NCBI Taxonomy ID
is Taxon A an Infraspecies?
No
Taxon A #2
Common Name
-
Synonyms
-
Rank
species
Lineage
Show more ... Brachycera; Muscomorpha; Eremoneura; Cyclorrhapha; Schizophora; Acalyptratae; Ephydroidea; Drosophilidae; Drosophilinae; Drosophilini; Drosophila; Sophophora; melanogaster group; melanogaster subgroup
NCBI Taxonomy ID
is Taxon A an Infraspecies?
No
Taxon B
Common Name
-
Synonyms
Drosophila sechellia Tsacas and Bachli, 1981
Rank
species
Lineage
Show more ... Brachycera; Muscomorpha; Eremoneura; Cyclorrhapha; Schizophora; Acalyptratae; Ephydroidea; Drosophilidae; Drosophilinae; Drosophilini; Drosophila; Sophophora; melanogaster group; melanogaster subgroup
NCBI Taxonomy ID
is Taxon B an Infraspecies?
No
GENOTYPIC CHANGE
UniProtKB
Drosophila melanogaster
GenebankID or UniProtKB
Presumptive Null
Yes
Molecular Type
Aberration Type
SNP
SNP Coding Change
Nonsense
Molecular Details of the Mutation
amino acid change at position 48 which converts the terminal glutamine residue of the propeptide region to a stop codon, and is predicted to generate a truncated version of the PPO3 protein
Experimental Evidence
Taxon A Taxon B Position
Codon - - -
Amino-acid Glu STP 48
Authors
Dudzic JP; Kondo S; Ueda R; Bergman CM; Lemaitre B
Abstract
The diversification of immune systems during evolution involves the expansion of particular gene families in given phyla. A better understanding of the metazoan immune system requires an analysis of the logic underlying such immune gene amplification. This analysis is now within reach due to the ease with which we can generate multiple mutations in an organism. In this paper, we analyze the contribution of the three Drosophila prophenoloxidases (PPOs) to host defense by generating single, double and triple mutants. PPOs are enzymes that catalyze the production of melanin at the site of infection and around parasites. They are the rate-limiting enzymes that contribute to the melanization reaction, a major immune mechanism of arthropods. The number of PPO-encoding genes is variable among insects, ranging from one in the bee to ten in the mosquito.

By analyzing mutations alone and in combination, we ascribe a specific function to each of the three PPOs of Drosophila. Our study confirms that two PPOs produced by crystal cells, PPO1 and PPO2, contribute to the bulk of melanization in the hemolymph, upon septic or clean injury. In contrast, PPO3, a PPO restricted to the D. melanogaster group, is expressed in lamellocytes and contributes to melanization during the encapsulation process. Interestingly, another overlapping set of PPOs, PPO2 and PPO3, achieve melanization of the capsule upon parasitoid wasp infection.

The use of single or combined mutations allowed us to show that each PPO mutant has a specific phenotype, and that knocking out two of three genes is required to abolish fully a particular function. Thus, Drosophila PPOs have partially overlapping functions to optimize melanization in at least two conditions: following injury or during encapsulation. Since PPO3 is restricted to the D. melanogaster group, this suggests that production of PPO by lamellocytes emerged as a recent defense mechanism against parasitoid wasps. We conclude that differences in spatial localization, immediate or late availability, and mode of activation underlie the functional diversification of the three Drosophila PPOs, with each of them having non-redundant but overlapping functions.
Additional References
RELATED GEPHE
Related Genes
No matches found.
Related Haplotypes
No matches found.
EXTERNAL LINKS
COMMENTS
There is also a loss of PPO3 expression in D. sechellia (the causal mutation(s) are unknown)
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