Lysine provisioning by horizontally acquired genes promotes mutual dependence between whitefly and two intracellular symbionts

Horizontal gene transfer is widespread in insects bearing intracellular symbionts. Horizontally transferred genes (HTGs) are presumably involved in amino acid synthesis in sternorrhynchan insects. However, their role in insect-symbiont interactions remains largely unknown. We found symbionts Portiera, Hamiltonella and Rickettsia possess most genes involved in lysine synthesis in the whitefly Bemisia tabaci MEAM1 although their genomes are reduced. Hamiltonella maintains a nearly complete lysine synthesis pathway. In contrast, Portiera and Rickettsia require the complementation of whitefly HTGs for lysine synthesis and have lysE, encoding a lysine exporter. Furthermore, each horizontally transferred lysine gene of ten B. tabaci cryptic species shares an evolutionary origin. We demonstrated that Hamiltonella did not alter the titers of Portiera and Rickettsia or lysine gene expression of Portiera, Rickettsia and whiteflies. Hamiltonella also did not impact on lysine levels or protein localization in bacteriocytes harboring Portiera and ovaries infected with Rickettsia. Complementation with whitefly lysine synthesis HTGs rescued E. coli lysine gene knockout mutants. Silencing whitefly lysA in whiteflies harboring Hamiltonella reduced lysine levels, adult fecundity and titers of Portiera and Rickettsia without influencing the expression of Hamiltonella lysA. Furthermore, silencing whitefly lysA in whiteflies lacking Hamiltonella reduced lysine levels, adult fecundity and titers of Portiera and Rickettsia in ovarioles. Therefore, we, for the first time, demonstrated an essential amino acid lysine synthesized through HTGs is important for whitefly reproduction and fitness of both obligate and facultative symbionts, and it illustrates the mutual dependence between whitefly and its two symbionts. Collectively, this study reveals that acquisition of horizontally transferred lysine genes contributes to coadaptation and coevolution between B. tabaci and its symbionts.

Amino acid synthesis loss in parasitoid wasps and other hymenopterans

Insects utilize diverse food resources which can affect the evolution of their genomic repertoire, including leading to gene losses in different nutrient pathways. Here, we investigate gene loss in amino acid synthesis pathways, with special attention to hymenopterans and parasitoid wasps. Using comparative genomics, we find that synthesis capability for tryptophan, phenylalanine, tyrosine, and histidine was lost in holometabolous insects prior to hymenopteran divergence, while valine, leucine, and isoleucine were lost in the common ancestor of Hymenoptera. Subsequently, multiple loss events of lysine synthesis occurred independently in the Parasitoida and Aculeata. Experiments in the parasitoid Cotesia chilonis confirm that it has lost the ability to synthesize eight amino acids. Our findings provide insights into amino acid synthesis evolution, and specifically can be used to inform the design of parasitoid artificial diets for pest control.

Survival strategies of Enterococcus mundtii in the gut of Spodoptera littoralis: a live report

The complex interaction between a higher organism and its resident gut flora is a subject of immense interest in the field of symbiosis. Many insects harbor a complex community of microorganisms in their gut. Larvae of Spodoptera littoralis, a lepidopteran pest which is prevalent in tropical and subtropical regions of the world, have a tube-like gut structure containing a simple bacterial community. This community varies both spatially (along the length of the gut) and temporally (during the life cycle of the insect).To monitor the dynamics and rapid adaptation of microbes to the gut conditions, a GFP-tagged reporter E. mundtii was constructed. After feeding to early instar S. littoralis larvae, the tagged-microbes recovered from the fore and hind guts by flow cytometry. The fluorescent reporter confirmed the persistence of E. mundtii in the gut. RNA-sequencing of the sorted bacteria highlighted various strategies that the symbiont employs to survive, including upregulated pathways for tolerating alkaline stress, forming biofilms and two-component signaling systems, resisting oxidative stress and quorum sensing. Although these symbionts depend on the host for amino acid and fatty acids, differential regulation among various metabolic pathways points to an enriched lysine synthesis pathway in the hindgut of the larvae.

Expression of the NADP+-Dependent Formate Dehydrogenase Gene from Pseudomonas Increases the Lysine Production in Corynebacterium glutamicum

Thepsefdh_D221Q gene coding for a mutant formate dehydrogenase (PseFDG_D221Q) from Pseudomonas, which catalyzes the formate oxidation with the simultaneous formation of NADPH, has been expressed in the cells of lysine-producing Corynebacterium glutamicum strains. The psefdh_D221Q gene was introduced into С. glutamicum strains as part of an autonomous plasmid or was integrated into the chromosome with simultaneous inactivation of host formate dehydrogenase genes. It was shown that the С. glutamicum strains with NADP+ -dependent formate dehydrogenase have an increased level of L-lysine synthesis in the presence of formate, if their own formate dehydrogenase is inactivated. L-lysine, formate dehydrogenase, NADPH, Corynebacterium glutamicum The work was carried out using the equipment of the Multipurpose Scientific This work was carried out on the equipment of the Multipurpose Scientific Installation of «All-Russian Collection of Industrial Microorganisms», National Bio-Resource Center, NRC «Kurchatov Institute»- GosNIIgenetika. This work was financially supported by the Ministry of Education and Science of Russia (Unique Project Identifier - RFMEFI61017X0011).