Functional analysis of the role ofeyes absentandsine oculisin the developing eye of the cricketGryllus bimaculatus

Abstract

In the cricket Gryllus bimaculatus, a hemimetabolous insect, the compound eyes begin to form in the embryo and increase 5-6 fold in size during the postembryonic development of the nymphal stage. Retinal stem cells in the anteroventral proliferation zone (AVPZ) of the nymphal eye proliferate to increase retinal progenitors, which then differentiate to form new ommatidia in the anterior region of the eye. However, mechanisms underlying this type of eye formation have not been well elucidated yet. Here, we found that the homologues of the retinal determination transcription factor genes of eyes absent (eya) and sine oculis (so) are expressed during the cricket embryonic eye formation. eya is also expressed intensely in the AVPZ of the nymphal eye. To explore their functions, we performed knockdown by RNA interference (RNAi). Knockdown of Gb'eya resulted in loss of the embryonic eye. In the nymphal eye, RNAi against Gb'eya or Gb'so impaired retinal morphology by apparently transforming cornea structures into head cuticle. These results imply that Gb'eya and Gb'so are essential for the differentiation of the retinal progenitor cells and maintaining retinal structures during eye development.

Hexapoda: Comparative Aspects of Later Embryogenesis and Metamorphosis

“…Likewise, the expression of eya and so in the eye lobes of the orthopterans Schistocerca (Dong and Friedrich 2005 ) and Gryllus (Inoue et al 2004 ) precedes the appearance of eyes during embryogenesis. Consistent with the function of eya in Drosophila and Tribolium , RNAi targeting embryonic eye expression in Gryllus causes the loss of compound eyes (Takagi et al 2012 ). These results support ancestral roles of eya and so in specifying eye primordia during embryogenesis in a large clade of hexapods.…”

“…3.27D-E ). The embryonic expression patterns of eya and so in Gryllus (Takagi et al 2012 ) and Schistocerca (Dong and Friedrich 2005 ), dac in Gryllus (Inoue et al 2004 ), and wg in Schistocerca (Dong and Friedrich 2005 ) are consistent with the eye patterning functions of these genes in Drosophila (Friedrich et al 2013 ). However, in Schistocerca , dpp is expressed in a dorsal region anterior to the morphogenetic furrow and at high levels in a stripe posterior to the morphogenetic furrow, rather than in the morphogenetic furrow as it is in Drosophila (Friedrich and Benzer 2000 ).…”

Ancient default activators of terminal photoreceptor differentiation in the pancrustacean compound eye: the homeodomain transcription factors Otd and Pph13

“…In addition to Drosophila, studies of compound eye development have been initiated in emerging pancrustacean model species that include the red flour beetle Tribolium castaneum [12], the grasshopper Schistocerca americana [13], the two-spotted cricket Gryllus bimaculatus [14,15], and, most recently, the water fleas Daphnia pulex and Daphnia magna [16]. Not surprisingly, these models differ in many visually-relevant features, given their diversified visual ecologies.…”

Opsin evolution and expression in Arthropod compound Eyes and Ocelli: Insights from the cricket Gryllus bimaculatus

“…Each compound eye ( C ) features a specialized dorsal rim area (DRA) and a ventral band (not marked, as its exact position is not known). Eye size increases from one larval stage to the next by adding new ommatidia along a budding zone at the anterior margin of the eye [42-44]. …”

“…They grow from one larval stage to the next by the addition of new ommatidia along a budding zone at the anterior margin of the eye [42-44]. In the adult, a compound eye comprises about 4600 ommatidia [43].…”