PgmNr D1201: Variable Effects of eRpL22 Family Paralogue Depletion on Eye Development in Drosophila melanogaster.

Authors:
B. W. Gershman; V. C. Ware


Institutes
Lehigh University, Bethlehem, PA.


Keyword: ectodermal derivatives

Abstract:

In D. melanogaster ribosomal protein (Rp) eRpL22-like has a tissue-specific expression pattern in the testis and eye (Kearse et al., 2011), compared to its ubiquitously expressed paralogue eRpL22.  Consistent with a ribosomal role, these paralogues are structurally similar within the rRNA binding domain (C terminus). Yet, considerable sequence divergence within the N terminal domain of each paralogue suggests the possibility of functionally divergent roles as components of ribosomes or as proteins functioning in other pathways.  The developmental significance of differential expression of eRpL22 paralogues is poorly understood.  Here we focus on the requirements for eRpL22 paralogues in three stages (3rd instar larva, midpupa, adult) of eye development using an RNAi-mediated Gal4-UAS strategy for tissue-specific paralogue knockdown, followed by immunohistochemistry to determine paralogue localization and score differences in eye development phenotypes for each paralogue.  eRpL22 is ubiquitously expressed, but eRpL22-like localization is tissue/cell-specific depending on developmental stage. In 3rd instar larva, eRpL22-like is detected at low levels within the cytoplasm of the eye disc proper; however, within the peripodial membrane, the cytoplasmic distribution of eRpL22-like is polarized toward the disc. In pupal stages, eRpL22-like is highly enriched within the developing inter-ommatidial bristle (IOB) complex. In adult tissue, localization of eRpL22-like shifts from the IOB complex to the ring of accessory cells surrounding each ommatidia (2° pigment, 3° pigment, IOB complex). Non-overlapping localization patterns in different cell/tissues is suggestive of specific functional roles for eRpL22 paralogues.  We then compared eRpL22 paralogue localization during eye development following paralogue knockdown. eyeless-Gal4 induced knockdown affects early mitotic ells while GMR-Gal4 induced knockdown affects differentiated cells. eyeless-Gal4- mediated eRpL22 depletion results in ablation of head and eye structures. In contrast, no notable effect on gross eye morphology or the head is apparent with eyeless-Gal4 mediated eRpL22-like depletion.  GMR-Gal4 mediated eRpL22 depletion leads to ommatidia disorganization and generation of a late onset eye lesion; however, eRpL22-like knockdown with GMR-Gal4 generates a bristle-specific defect.  Notably, a different phenotype results from paralogue-specific knockdown using the same Gal4 driver, suggesting non-redundant (and specialized) roles for each paralogue during eye development. Future work will include attempts to rescue paralogue-specific knockdown phenotypes with overexpression of the cognate paralogue to determine the degree, if any, of functional redundancy in the eRpL22 family.



Flybase Genetic Index:
1. FlyBase gene symbol: Dmel\RpL22-like; FBgn: FBgn0034837
2. FlyBase gene symbol: Dmel\RpL22; FBgn: FBgn0015288