Rickettsia increasing female fecundity and sex ratio shift by host hormone modulating in whitefly

What is it about?

Heritable symbionts are common among animals in nature, but the molecular mechanisms underpinning symbiont invasions of host populations have been elusive. In this study, we demonstrate the spread of Rickettsia in an invasive agricultural pest, the whitefly Bemisia tabaci Mediterranean (MED), across northeastern China from 2018 to 2023. Here, we show that the beneficial symbiont Rickettsia spreads by manipulating host hormone signals. Our analyses suggest that Rickettsia have been horizontally acquired by B. tabaci MED from another invasive whitefly B. tabaci Middle East-Asia Minor 1 during periods of coexistence. Rickettsia is transmitted maternally and horizontally from female B. tabaci MED individuals. Rickettsia infection enhances fecundity and results in female bias among whiteflies. Our findings reveal that Rickettsia infection stimulates juvenile hormone (JH) synthesis, in turn enhancing fecundity, copulation events, and the female ratio of the offspring. Consequently, Rickettsia infection results in increased whitefly fecundity and female bias by modulating the JH pathway. More female progeny facilitates the transmission of Rickettsia. This study illustrates that the spread of Rickettsia among invasive whiteflies in northeastern China is propelled by host hormone regulation. Such symbiont invasions lead to rapid physiological and molecular evolution in the host, influencing the biology and ecology of an invasive species.

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Photo by National Cancer Institute on Unsplash

Photo by National Cancer Institute on Unsplash

Why is it important?

The symbionts can spread in hosts by horizontal transmission as well as fitness effect and reproductive manipulation. However, the molecular mechanisms underlying host fitness effect and reproductive manipulation contributing to symbiont infection in host populations are largely unclear. Here, we demonstrate the spread of Rickettsia, which was horizontally acquired from Bemisia tabaci Middle East-Asia Minor 1, in B. tabaci Mediterranean, throughout northeastern China in 6 y. Rickettsia infection resulted in increased whitefly fecundity and female bias by stimulating juvenile hormone synthesis. The production of more female progeny facilitates Rickettsia transmission. Our results demonstrate that bacterial symbionts impact insect reproduction by modulating hormone signals. This study highlights the important role of host physiological and molecular regulation in the dissemination of symbionts in invasive insects.