Yellow-g and Yellow-g2 proteins are required for egg desiccation resistanceand temporal pigmentation in the Asian tiger mosquito, Aedes albopictus

Presenting Author(s)

MN

Mi Young Noh

Assistant Professor
Chonnam National University
gwangju, Kwangju-jikhalsi, Republic of Korea

Co-Author(s)

SK

Sung Hyun Kim

Chonnam National University
Gwangju, Kwangju-jikhalsi, Republic of Korea
Maureen J. Gorman

Research Associate Professor
Kansas State University
Manhattan, Kansas, United States
KK

Karl Kramer

Professor
Kansas State University
Manhattan, Kansas, United States
SM

Subbaratnam Muthukrishnan

Professor
Kansas State University
Manhattan, Kansas, United States
YA

Yasuyuki Arakane

Professor
Chonnam National University
Gwangju, Kwangju-jikhalsi, Republic of Korea

Eggs from Aedes mosquitoes exhibit desiccation resistance that helps them survive and spread as human disease vectors. Previous studies have suggested that eggshell/chorion melanization and/or serosal cuticle formation are important factors for desiccation resistance. Here, we analyzed the functional importance of two ovary-specific yellow genes, AalY-g and AalY-g2, in resistance to egg desiccation of Aedes albopictus, a species in which neither timing of the melanization nor temporal development of serosal cuticle is correlated with desiccation resistance. Injections of dsAalY-g or dsAalY-g2 (dsRNAs) into adult females have no effect on fecundity. However, initial melanization is delayed by 1-2 h with eggshells eventually becoming black similar to the pigmentation observed in dsEGFP control eggs. In addition, the shape of the dsAalY-g and dsAalY-g2-depletedeggs is abnormally crescent-shaped and the outermost exochorion is fragile and becomes partially peeled off. dsEGFP control eggs acquire resistance to desiccation (ERD) between 18 and 24 h after oviposition (HAO). However, ~80% of the 24 HAO dsAalY-g and dsAalY-g2 eggs collapse, when they are transferred to a low humidity environment. Furthermore, no electron-dense outer endochorion is evident in either dsAalY-g or dsAalY-g2 eggs. These results suggest that AalY-g and AalY-g2 help to regulate the timing of eggshell darkening and are required for integrity of the exochorion as well as rigidity, normal morphology and formation of the outer endochorion, a structure that apparently is critical for egg desiccation resistance in Ae. albopictus.