Conservation of transcriptional elements in the obligate symbiont of the whitefly Bemisia tabaci

Abstract

Background Bacterial symbiosis is widespread in arthropods, especially in insects. Some of the symbionts undergo a long-term co-evolution with the host, resulting in massive genome decay. One particular consequence of genome decay is thought to be the elimination of transcriptional elements within both the coding region and intergenic sequences. In the whitefly Bemisia tabaci species complex, the obligate symbiont Candidatus Portiera aleyrodidarum is of vital importance in nutrient provision, and yet little is known about the regulatory capacities of it. Methods Portiera genomes of two whitefly species in China were sequenced and assembled. Gene content of these two Portiera genomes was predicted, and then subjected to Kyoto Encyclopedia of Genes and Genomes pathway analysis. Together with two other Portiera genomes from whitefly species available previously, four Portiera genomes were utilized to investigate regulatory capacities of Portiera, focusing on transcriptional elements, including genes related with transcription and functional elements within the intergenic spacers. Results Comparative analyses of the four Portiera genomes of whitefly B. tabaci indicate that the obligate symbionts Portiera is similar in different species of whiteflies, in terms of general genome features and possible functions in the biosynthesis of essential amino acids. The screening of transcriptional factors suggests compromised ability of Portiera to regulate the essential amino acid biosynthesis pathways. Meanwhile, thermal tolerance ability of Portiera is indicated with the detection of a σ32 factor, as well as two predicted σ32 binding sites. Within intergenic spacers, functional elements are predicted, including 37 Shine-Dalgarno sequences and 34 putative small RNAs.

Whitefly endosymbionts: IPM opportunity or tilting at windmills?

“…The genome of Portiera has been severely reduced during its co-evolution with the host and is around 350,000 base pairs long and with only around 300 genes (Zhu et al 2019 ; Jiang et al 2012 ; Santos-Garcia et al 2012 ). Its genes code enzymes involved in essential amino acid synthesis, carotenoid synthesis, information transfer, and oxidative phosphorylation (Calle-Espinosa et al 2016 ; Santos-Garcia et al 2012 ; Sloan and Moran 2012 ).…”

Nutritional Relationship between Bemisia tabaci and Its Primary Endosymbiont, Portiera aleyrodidarum, during Host Plant Acclimation

“…One possible explanation of the improved performance of B. tabaci is that it manipulates the expression of essential amino acid biosynthesis genes of P. aleyrodidarum, thus helping it to overcome the changing nutrient conditions in the phloem sap. This explanation is supported by a study revealing that none of the regulatory genes related to amino acid biosynthesis were found in P. aleyrodidarum, which suggests that it is B. tabaci, not P. aleyrodidarum, that can regulate the biosynthesis of amino acids [39]. Moreover, one generation may be insufficient for B. tabaci to respond to the different diet conditions between the phloem sap of cotton and Chinese kale, which could explain why the fecundity of first-generation whiteflies was lower than that of the original colony.…”

Cytotype Affects the Capability of the Whitefly Bemisia tabaci MED Species To Feed and Oviposit on an Unfavorable Host Plant

“…Differences related to genetic and/or gene expression variability of the P-symbiont among cytotypes also seems unlikely, given the low genetic variability and the constant metabolic capabilities of “ Ca. Portiera” within the B. tabaci species complex ( 38 , 44 , 73 – 75 ) and the almost complete loss in the “ Ca. Portiera” genome of elements for gene expression regulation (that seems to be ensured by the whitefly host) ( 73 ).…”

“…Portiera” within the B. tabaci species complex ( 38 , 44 , 73 – 75 ) and the almost complete loss in the “ Ca. Portiera” genome of elements for gene expression regulation (that seems to be ensured by the whitefly host) ( 73 ). Conversely, considering their genomic capabilities and based on the results presented above, S-symbionts are promising candidates to explain the differences observed between the three B. tabaci lines considered here.…”