Whitefly Endosymbionts: Biology, Evolution, and Plant Virus Interactions

SIMPLE SUMMARY: Whiteflies feed on plant sap and cause many problems on agricultural crops around the world. Whiteflies have endosymbiotic bacteria in cells inside their bodies that help them to feed on plants. Therefore, the sweetpotato whitefly feeds on a wide range of plants including many vegetable crops, and there are different types of these bacteria which do not all occur in the same whitefly population. In this paper, we focus on endosymbiotic bacteria that are associated with different biotypes of the sweetpotato whitefly with emphasis on their biological characteristics, diversity, and their interactions with whitefly-transmitted plant viruses. This information will be useful to the scientific community for the development of strategies to disrupt these bacteria and provide better whitefly control. ABSTRACT: Whiteflies (Hemiptera: Aleyrodidae) are sap-feeding global agricultural pests. These piercing-sucking insects have coevolved with intracellular endosymbiotic bacteria that help to supplement their nutrient-poor plant sap diets with essential amino acids and carotenoids. These obligate, primary endosymbionts have been incorporated into specialized organs called bacteriomes where they sometimes coexist with facultative, secondary endosymbionts. All whitefly species harbor the primary endosymbiont Candidatus Portiera aleyrodidarum and have a variable number of secondary endosymbionts. The secondary endosymbiont complement harbored by the cryptic whitefly species Bemisia tabaci is particularly complex with various assemblages of seven different genera identified to date. In this review, we discuss whitefly associated primary and secondary endosymbionts. We focus on those associated with the notorious B. tabaci species complex with emphasis on their biological characteristics and diversity. We also discuss their interactions with phytopathogenic begomoviruses (family Geminiviridae), which are transmitted exclusively by B. tabaci in a persistent-circulative manner. Unraveling the complex interactions of these endosymbionts with their insect hosts and plant viruses could lead to advancements in whitefly and whitefly transmitted virus management.