Biology subjects

Fukatsu, T.

Publications and source records attributed to Fukatsu, T..

16 recordsLinked to original sources

bioRxiv2026

Global transcriptional rewiring provides recurrent evolutionary routes to insect-Escherichia coli mutualism

Microbial symbionts often evolve specialized functions that compensate for host nutritional deficiencies, yet the evolutionary routes by which such mutualisms arise remain poorly understood. Here, using an experimental symbiosis between the stinkbug Plautia stali and Escherichia coli, we investigated the early evolution of insect-bacterium mutualism. Among 144 independently evolved bacterial lineages, six acquired the ability to improve host performance. Four lineages carried independent disruptive mutations in cyaA, disabling carbon catabolite repression and thereby increasing the essential amino acid tryptophan. The remaining two lineages evolved through nonsynonymous mutations in rpoB or rpoD, encoding core components of the transcriptional machinery. Transcriptomic analyses revealed extensive regulatory rewiring in both mutants, including marked upregulation of biosynthetic pathways for branched-chain essential amino acids. Our results identify global transcriptional regulatory systems as major evolutionary targets for the emergence of mutualism and demonstrate how large-effect regulatory mutations can rapidly generate host-beneficial traits. (146 < 150 words)

evolutionary biology↗

bioRxiv2026

Adaptive laboratory evolution of a minimal cell to low temperature

Temperature is a fundamental constraint on life. Most organisms adapt to temperature change through complex regulatory and stress-response systems. Whether such adaptation is possible in a genomically minimal cell remains unclear. Here, adaptive laboratory evolution was performed on the minimal genome bacterium JCVI-syn3B, shifting growth from 37{degrees}C to 25{degrees}C, a temperature at which the original strain cannot grow. After 40 serial passages, the evolved strains exhibited robust growth at 25{degrees}C. Multi-omics analyses revealed the adaptation mechanisms including increased mRNA turnover, enhanced DNA unwinding and stabilization of replication intermediates, elevated glycerolipid synthesis, and upregulation of division proteins associated with Z-ring assembly. Whole-genome transplantation was performed to distinguish genetic or non-genetic contributions, demonstrating that the cold-adapted phenotype was largely genetically encoded. These results indicated that even a minimal cell retains substantial evolvability and highlight its potential as a tractable research platform for cellular and evolutionary biology.

evolutionary biology↗

bioRxiv2026

Symbiotic Escherichia coli strains can better colonize host stinkbugs and outcompete natural symbiotic bacteria, but confer less fitness benefits

The stinkbug Plautia stali harbors essential gut symbiotic bacteria of the genus Pantoea, whose natural strains differ in cultivability and host benefits. Using this system, we evaluated how laboratory-evolved and genetically-engineered symbiotic Escherichia coli strains compete against native Pantoea symbionts and how they influence host fitness. In single infection assays, the native uncultivable symbiont Sym A conferred the highest host performance, whereas the evolved (CmL05G13) and artificial ({Delta}cyaA) symbiotic E. coli strains supported host survival at levels comparable to cultivable Pantoea symbionts (Sym C-F). In competitive co-infection assays, the symbiotic E. coli strains generally showed unexpectedly strong colonization ability. CmL05G13 outcompeted all the cultivable symbionts Sym C-F and even displaced the native uncultivable symbiont Sym A, whereas {Delta}cyaA and the nonsymbiotic control E. coli {Delta}intS were dominated by Sym A at the adult stage. Despite their superior infection competitiveness, the symbiotic E. coli strains provided limited reproductive benefits, behaving as "cheater-like" associates. They were able to invade and dominate the symbiotic organ but failed to match the fitness contributions of native symbionts. These results demonstrate that the experimentally evolved E. coli can rapidly acquire strong colonization ability surpassing that of the natural symbionts that have coevolved with P. stali in nature. At the same time, the mismatch between infection success and host fitness benefits highlights potential evolutionary conflicts and provides an experimental model for studying the dynamics of cheating, mutualism, and symbiont replacement in vertically transmitted symbioses. IMPORTANCEUnderstanding how novel symbionts invade and displace long-term mutualists is central to the evolution of symbiosis. This study demonstrates that Escherichia coli, originally a nonsymbiotic bacterium, can rapidly evolve potent colonization ability and even outcompete native Pantoea symbionts of the stinkbug Plautia stali. Meanwhile, these competitive E. coli strains confer markedly lower reproductive benefits compared with the native symbionts that have developed intimate mutualistic association with host P. stali over evolutionary time, revealing a striking decoupling between infection success and host fitness. This finding highlights the potential for cheater-like microbes to invade vertically transmitted symbioses and destabilize coevolved partnerships. By combining experimental evolution, controlled co-infections, and quantitative analyses, the P. stali-E. coli experimental symbiotic system provides a powerful model for studying the mechanisms and evolutionary dynamics of mutualism, cheating, and symbiont replacement.

microbiology↗

bioRxiv2025

Uric acid accumulation in cockroach wings

Cockroaches, embracing some 4,500 species in the world, are found in a variety of environments including human settlements. The ecological success of cockroaches is attributable to the ability to endure long periods of starvation and to thrive on nutritionally poor diets, which is underpinned by the capability of storing their own nitrogenous waste products as uric acid in the fat body and also by the endosymbiosis with bacteriocyte-dwelling bacteria Blattabacterium that recycle the stored uric acid for synthesis of amino acids. Previous histological studies on cockroaches described that uric acid is accumulated within the fat body, especially in urocytes. Here we report that cockroaches also accumulate uric acid in the wings. In our observation of the German cockroach Blattella germanica under different nutritional conditions, we found that well-fed cockroaches exhibited whitish aggregates in the wing veins, which is ascribed to accumulation of uric acid granules. The uric acid granules in the wings disappeared by starvation and were restored by feeding in B. germanica. The uric acid granules in the wings were found not only in B. germanica but also in other diverse cockroach species.

physiology↗

bioRxiv2025

Cockroach bacteriocytes migrate into the ovaries for vertical transmission of the bacterial endosymbiont Blattabacterium

Diverse insect groups are obligatorily associated with and dependent on specific microorganisms as essential mutualistic partners that are usually maintained in specialized cells or organs, called bacteriocytes or symbiotic organs. Many organisms with symbiotic microorganisms have developed elaborate vertical transmission mechanisms, which are thought to be important for the evolution of intimate symbiotic relationships with microorganisms. One such case is the cockroach-Blattabacterium endosymbiosis, in which the symbiotic bacteria have been evolutionarily conserved and co-speciated with the host insects with stable vertical symbiont transmission via ovarial passage. While classical histological descriptions and recent electron microscopic observations have reported the vertical symbiont transmission processes in some cockroach-Blattabacterium associations, the full picture of the infection dynamics has not been fully understood. In this study, we conducted detailed histological and cytological observations of the localization of the bacteriocytes and the symbiotic bacteria during the postembryonic development of the German cockroach Blattella germanica. We found that the symbiont-filled bacteriocytes migrate into and associate with nymphal ovaries and are subsequently eliminated from adult ovaries, suggesting that symbiont infection to the ovaries may only occur during nymphal stages. We also found that the symbiotic bacteria are localized in the space between each oocyte and surrounding follicle cells, the symbiont-localized space is interconnected between neighboring oocytes, and therefore the symbiotic bacteria can move across oocytes within the same ovariole, suggesting the possibility that the symbiont-infected oocytes may serve as the source of symbiont supply to developing young oocytes upstream in the same ovariole. Based on these observations, we provide a hypothesis as to how the postembryonic developmental dynamics of the bacteriocytes are integrated into the vertical symbiont transmission and functioning in the cockroach-Blattabacterium endosymbiosis.

developmental biology↗

bioRxiv2024

Robust and highly efficient transformation method for a minimal Mycoplasma cell

Mycoplasmas have been widely investigated for their pathogenicity, as well as for genomics and synthetic biology. Conventionally, transformation of mycoplasmas was not highly efficient, and due to the low transformation efficiency, large amounts of DNA and recipient cells were required for that purpose. Here we report a robust and highly efficient transformation method for the minimal cell JCVI-syn3B, which was created through streamlining of the genome of Mycoplasma mycoides. When the growth states of JCVI-syn3B were examined in detail by focusing on such factors as pH, color, absorbance, CFU, and transformation efficiency, we found that the growth phase after the lag phase can be divided into three distinct phases, of which the highest transformation efficiency was observed during the early-exponential growth phase. Notably, we attained the transformation efficiency up to 4.4 x 10-2 transformants per cell per g plasmid DNA. We developed a method to obtain several hundred to several thousand transformants with less than 0.2 mL of cultured cells and 10 ng of plasmid DNA. Moreover, we established a transformation method using frozen stock of transformation-ready cells. These procedures and information could simplify and enhance the transformation process of minimal cells, facilitating advanced genetic engineering and biological research using minimal cells. IMPORTANCEMycoplasmas are parasitic and pathogenic bacteria for many animals. They are also useful bacteria to understand cellular process of life and for bioengineering because of their simple metabolism, small genomes and cultivability. Genetic manipulation is crucial for these purposes, but transformation efficiency in mycoplasmas is typically quite low. Here we report a highly efficient transformation method for the minimal genome mycoplasma JCVI-syn3B. Using this method, transformants can be obtainable only 10 nanograms of plasmid DNA, which is around one-thousandth amount required for traditional mycoplasma transformations. Moreover, we established a convenient method using frozen stocks of transformation-ready cells. These improved methods play a crucial role in further studies using minimal cells.

microbiology↗

bioRxiv2024

Tryptophanase disruption underlies the evolution of insect-bacterium mutualism

Animal-microbe symbioses are omnipresent, where both partners often gain benefits as mutualists. How such mutualism has evolved between originally unrelated organisms is of interest. Here we report that, using an experimental symbiotic system between the stinkbug Plautia stali and the model bacterium Escherichia coli, disruption of a single bacterial gene tnaA encoding tryptophanase makes E. coli mutualistic to P. stali. Survey of natural bacterial mutualists across wild populations of P. stali and other stinkbug species uncovered that their Pantoea-allied symbionts consistently lack tnaA gene. Some Pantoea species like P. ananatis retain tnaA gene and cannot establish symbiosis with P. stali, but tnaA-disrupted P. ananatis partially restored the symbiotic capability. When a natural Pantoea mutualist of P. stali was transformed with a functional tna operon, its symbiotic capability reduced significantly. Our finding suggests that tryptophanase disruption may have facilitated the evolution of gut bacterial mutualists in insects.

evolutionary biology↗

bioRxiv2024

Frequent and asymmetric cell division in endosymbiotic bacteria of cockroaches

Many insects are obligatorily associated with and dependent on specific microbial species as essential mutualistic partners. In the host insects, such microbial mutualists are usually maintained in specialized cells or organs, called bacteriocytes or symbiotic organs. Hence, potentially exponential microbial growth cannot be realized but must be strongly constrained by spatial and resource limitations within the host cells or tissues. How such endosymbiotic bacteria grow, divide and proliferate is important for understanding the interactions and dynamics underpinning intimate host-microbe symbiotic associations. Here we report that Blattabacterium, the ancient and essential endosymbiont of cockroaches, exhibits unexpectedly high rates of cell division (20-58%) and, in addition, the cell division is asymmetric (average asymmetry index > 1.5) when isolated from the German cockroach Blattella germanica. The asymmetric division of endosymbiont cells at high frequencies was observed irrespective of host tissues (fat bodies vs. ovaries) or developmental stages (adults vs. nymphs vs. embryos) of B. germanica, and also observed in several different cockroach species. By contrast, such asymmetric and frequent cell division was observed neither in Buchnera, the obligatory bacterial endosymbiont of aphids, nor in Pantoea, the obligatory bacterial gut symbiont of stinkbugs. Comparative genomics of cell division-related genes uncovered that the Blattabacterium genome lacks the Min system genes that determine the cell division plane, which may be relevant to the asymmetric cell division. These observations combined with comparative symbiont genomics provide insight into what processes and regulations may underpin the growth, division and proliferation of such bacterial mutualists continuously constrained under within-host conditions. IMPORTANCEDiverse insects are dependent on specific bacterial mutualists for their survival and reproduction. Due to the long-lasting coevolutionary history, such symbiotic bacteria tend to exhibit degenerative genomes and suffer uncultivability. Because of their microbiological fastidiousness, the cell division patterns of such uncultivable symbiotic bacteria have been poorly described. Here, using fine microscopic and quantitative morphometric approaches, we report that, although bacterial cell division usually proceeds through symmetric binary fission, Blattabacterium, the ancient and essential endosymbiont of cockroaches, exhibits frequent and asymmetric cell division. Such peculiar cell division patterns were not observed with other uncultivable essential symbiotic bacteria of aphids and stinkbugs. Gene repertoire analysis revealed that the molecular machineries for regulating the bacterial cell division plane are lost in the Blattabacterium genome, suggesting the possibility that the general trend toward the reductive genome evolution of symbiotic bacteria may underpin their bizarre cytological/morphological traits.

microbiology↗

bioRxiv2024

Host range of naturally and artificially evolved symbiotic bacteria for a specific host insect

Diverse insects are intimately associated with specific symbiotic bacteria, where host and symbiont are integrated into an almost inseparable biological entity. These symbiotic bacteria usually exhibit host specificity, uncultivability, reduced genome size, and other peculiar traits relevant to their symbiotic lifestyle. How host-symbiont specificity is established at the very beginning of symbiosis is of interest but poorly understood. To gain insight into the evolutionary issue, we adopted an experimental approach using the recently developed evolutionary model of symbiosis between the stinkbug Plautia stali and Escherichia coli. Based on the laboratory evolution of P. stali-E. coli mutualism, we selected {Delta}cyaA mutant of E. coli as an artificial symbiont of P. stali that has established mutualism by a single mutation. In addition, we selected a natural cultivable symbiont of P. stali of relatively recent evolutionary origin. These artificial and natural symbiotic bacteria of P. stali were experimentally inoculated to symbiont-deprived newborn nymphs of diverse stinkbug species. Strikingly, the mutualistic E. coli was unable to establish infection and support growth and survival of all the stinkbug species except for P. stali, uncovering that host specificity can be established at a very early stage of symbiotic evolution. Meanwhile, the natural symbiont was able to establish infection and support growth and survival of several stinkbug species in addition to P. stali, unveiling that a broader host range of the symbiont has evolved in nature. Based on these findings, we discuss what factors are relevant to the establishment of host specificity in the evolution of symbiosis. IMPORTANCEHow does host-symbiont specificity emerge at the very beginning of symbiosis? This question is difficult to address, because it is generally difficult to directly observe the onset of symbiosis. However, recent development of experimental evolutionary approaches to symbiosis has brought about a breakthrough. Here we tackled this evolutionary issue using a symbiotic Escherichia coli created in laboratory and a natural Pantoea symbiont, which are both mutualistic to the stinkbug Plautia stali. We experimentally replaced essential symbiotic bacteria of diverse stinkbugs by the artificial and natural symbionts of P. stali, and evaluated whether the symbiotic bacteria evolved for a specific host can establish infection and support growth and survival of heterospecific hosts. Strikingly, the artificial symbiont showed strict host specificity to P. stali whereas the natural symbiont was capable of symbiosis with diverse stinkbugs, which provide insight into how host-symbiont specificity can be established at early evolutionary stages of symbiosis.

microbiology↗

bioRxiv2024

High temperature treatment optimized for symbiont suppression in an obligatory gut bacterial symbiosis in the stinkbug Plautia stali

In the era of global warming, much attention has been paid to the possibility that high temperature may influence diverse insects not only directly but also indirectly via effects on their symbiotic microorganisms. The stinkbug Plautia stali develops a midgut symbiotic organ that harbors a specific bacterial symbiont indispensable for its growth and survival. Being maintainable in laboratory and tractable experimentally, P. stali is recently highlighted as a model system to investigate the mechanisms underpinning insect-microbe symbiotic interactions. In this study, we reared newly-emerged adult insects of P. stali under different temperature conditions for 8 days and monitored how their symbiotic organs and symbiotic bacteria are affected. While all insects survived at temperatures from 25{degrees}C to 37{degrees}C, some insects died at 38{degrees}C, 39{degrees}C and 40{degrees}C, wherein mortality rates increased as temperature elevated. While the symbiotic organs of the normal insects exhibited vivid yellow color, the symbiotic organs of the insects reared at 35{degrees}C or higher frequently exhibited abnormal colors such as pale yellow, yellowish white, or white, the extent of which became more severe as temperature elevated. Symbiont quantification revealed that, while the symbiont titers were almost constant for 8 days at 25{degrees}C and 30{degrees}C, the symbiont titers on the 8th day drastically declined to 1/100 at 35 and 1/10000 at 37{degrees}C and 39{degrees}C. Based on these results, we propose that rearing at 37{degrees}C for a week is a recommended treatment regime by which the symbiont is effectively suppressed with minimal damage to the host insect.

physiology↗

bioRxiv2024

Defensive fungal symbiosis on insect hindlegs

Tympanal organs as "insect ears" have evolved repeatedly. Dinidorid stinkbugs were reported to possess a conspicuous tympanal organ on females hindlegs. Here we report an unexpected discovery that the stinkbugs "tympanal organ" is actually a novel symbiotic organ. The stinkbugs "tympanum" is not membranous but a porous cuticle, where each pore connects to glandular secretory cells. In reproductive females, the hindleg organ is covered with fungal hyphae growing out of the pores. Upon oviposition, the females skillfully transfer the fungi from the organ to the eggs. The eggs are quickly covered with hyphae and physically protected against wasp parasitism. The fungi are mostly benign Cordycipitaceae entomopathogens and show considerable diversity among insect individuals and populations, indicating environmental acquisition of specific fungal associates. These results uncover a novel external fungal symbiosis in which hosts elaborate morphological, physiological and behavioral specializations underpin the selective recruitment of benign entomopathogens for a defensive purpose.

microbiology↗

bioRxiv2023

Paleocene origin of a streamlined digestive symbiosis in leaf beetles

Timing the acquisition of a beneficial microbe relative to the evolutionary history of its host can shed light on the adaptive impact of a partnership. Here, we investigated the onset and molecular evolution of an obligate symbiosis between Cassidinae leaf beetles and Candidatus Stammera capleta, a {gamma}-proteobacterium. Residing extracellularly within foregut symbiotic organs, Stammera upgrades the digestive physiology of its host by supplementing plant cell wall-degrading enzymes. We observe that Stammera is a shared symbiont across tortoise and hispine beetles that collectively comprise the Cassidinae subfamily, despite differences in their folivorous habits. In contrast to its transcriptional profile during vertical transmission, Stammera elevates the expression of genes encoding digestive enzymes while in the foregut symbiotic organs, matching the nutritional requirements of its host. Symbiont acquisition during the Paleocene ([~]62 Mya) did not coincide with the origin of Cassidinae beetles, despite the widespread distribution of Stammera across the subfamily. Early-diverging lineages lack the symbiont and the specialized organs that house it. Reconstructing the ancestral state of host-beneficial factors revealed that Stammera encoded three digestive enzymes at the onset of symbiosis, including polygalacturonase - a pectinase that is universally shared. While non-symbiotic cassidines encode polygalacturonase endogenously, their repertoire of plant cell wall-degrading enzymes is more limited compared to symbiotic beetles supplemented with digestive enzymes from Stammera. Highlighting the potential impact of a symbiotic condition and an upgraded metabolic potential, Stammera-harboring beetles exploit a greater variety of plants and are more speciose compared to non-symbiotic members of the Cassidinae.

evolutionary biology↗

bioRxiv2023

Mechanisms underpinning morphogenesis of symbiotic organ specialized for hosting indispensable microbial symbiont in stinkbug

Microbial mutualists are pivotal for insect adaptation, which often entails the evolution of elaborate organs for symbiosis. Addressing what mechanisms underpin the development of such organs is of evolutionary interest. Here we investigated the stinkbug Plautia stali whose posterior midgut is transformed into a specialized symbiotic organ. Despite being a simple tube in newborns, it developed numerous crypts in four rows, whose inner cavity hosts a specific bacterial symbiont, during 1st to 2nd nymphal instar. Visualization of dividing cells revealed that active cell proliferation was coincident with the crypt formation, although spatial patterns of the proliferating cells did not reflect the crypt arrangement. Visualization of visceral muscles in the midgut, consisting of circular muscles and longitudinal muscles, uncovered that, strikingly, circular muscles exhibited a characteristic arrangement running between the crypts specifically in the symbiotic organ. Even in early 1st instar when no crypts were seen, two rows of epithelial areas delineated by bifurcated circular muscles were identified. In 2nd instar, crossing muscle fibers newly appeared and connected the adjacent circular muscles, whereby the midgut epithelium was divided into four rows of crypt-to-be areas. The crypt formation proceeded even in aposymbiotic nymphs, uncovering autonomous nature of the crypt development. We propose a mechanistic model of crypt formation wherein the spatial arrangement of muscle fibers and the proliferation of epithelial cells underpin the formation of crypts as midgut evaginations. IMPORTANCEDiverse organisms are associated with microbial mutualists, in which specialized host organs often develop for retaining the microbial partners. In the light of the origin of evolutionary novelties, it is important to understand what mechanisms underpin the elaborate morphogenesis of such symbiotic organs, which must have been shaped through interactions with the microbial symbionts. Using the stinkbug Plautia stali as a model, we demonstrated that visceral muscular patterning and proliferation of intestinal epithelial cells during early nymphal stages are involved in the formation of numerous symbiont-harboring crypts arranged in four rows in the posterior midgut to constitute the symbiotic organ. Strikingly, the crypt formation occurred normally even in symbiont-free nymphs, uncovering that the crypt development proceeds autonomously. These findings suggest that the crypt formation is deeply implemented into the normal development of P. stali, which must reflect the considerably ancient evolutionary origin of the midgut symbiotic organ in stinkbugs.

microbiology↗

bioRxiv2022

Cuticle supplementation and nitrogen recycling by a dual bacterial symbiosis in a family of xylophagous beetles (Coleoptera: Bostrichidae)

Many insects engage in stable nutritional symbioses with bacteria that supplement limiting essential nutrients to their host. While several plant sap-feeding Hemipteran lineages are known to be simultaneously associated with two or more endosymbionts with complementary biosynthetic pathways to synthesize amino acids or vitamins, such co-obligate symbioses have not been functionally characterized in other insect orders. Here, we report on the characterization of a dual co-obligate, bacteriome-localized symbiosis in a family of xylophagous beetles using comparative genomics, fluorescence microscopy, and phylogenetic analyses. Across the beetle family Bostrichidae, all investigated species harbored the Bacteroidota symbiont Shikimatogenerans bostrichidophilus that encodes the shikimate pathway to produce tyrosine precursors in its severely reduced genome, likely supplementing the beetles cuticle biosynthesis, sclerotisation, and melanisation. One clade of Bostrichid beetles additionally housed the co-obligate symbiont Bostrichicola ureolyticus that is inferred to complement the function of Shikimatogenerans by recycling urea and provisioning the essential amino acid lysine, thereby providing additional benefits on nitrogen-poor diets. Both symbionts represent ancient associations within the Bostrichidae that have subsequently experienced genome erosion and co-speciation with their hosts. While Bostrichicola was repeatedly lost, Shikimatogenerans has been retained throughout the family and exhibits a perfect pattern of co-speciation. Our results reveal that co-obligate symbioses with complementary metabolic capabilities occur beyond the well-known sap-feeding Hemiptera and highlight the importance of symbiont-mediated cuticle supplementation and nitrogen recycling for herbivorous beetles. Significance statementNutritional symbioses evolved frequently in insects and contribute diverse metabolites to their hosts physiology. Associations with dual symbionts providing complementary nutrients evolved in multiple Hemiptera lineages, compensating eroded biosynthetic capabilities of primary symbionts. Bostrichidae, a family of xylophagous beetles, harbor consistently a Flavobacterial symbiont encoding exclusively the Shikimate pathway to synthesis precursors of tyrosine. However, in two families a second, closely Flavobacterial symbiont capable of recycling urea and synthesizing lysine was retained. Both symbionts exhibit high genomic syntheny and tight co-cladogenesis with the host phylogeny, indicating ancestral, ecological highly beneficial symbioses.

evolutionary biology↗

bioRxiv2022

Seasonal polyphenism underlies the origin of a sterile caste in aphids

The origin of a sterile caste among eusocial animals has been a fundamental but still unresolved problem in understanding the evolution of biological complexity. At the origin of a sterile caste, recruitment of pre-existing plasticity may lead to produce physiologically, morphologically and behaviorally distinct caste phenotypes. Here, we provide convincing evidence that preexisting seasonal polyphenism has been recruited to generate a sterile soldier caste in host-alternating social aphids. We demonstrate that sterile soldier nymphs of Colophina aphids resemble those of monomorphic defensive nymphs produced in a different host-plant generation. Notably, the two morphs in the basal species show the closest similarity in morphology and gene expression among all morph pairs. Moreover, their evolutionary phenotypic changes along the phylogeny of four Colophina species are significantly correlated positively. These results suggest that they may share the common regulatory mechanisms of development, which underpin the heterochronic expression of monomorphic defenders on the different host plant leading to the evolution of a novel soldier phenotype. We further demonstrate that the monomorphic defenders can increase their inclusive fitness by killing predators eggs on a seasonally different host plant. Taken together, our findings suggest that preexisting plasticity that can gain indirect fitness benefits facilitates the early evolution of a sterile caste.

evolutionary biology↗

bioRxiv2022

Single mutation makes Escherichia coli an insect mutualist

We report an experimental system in which Escherichia coli evolves into an insect mutualist. When the essential gut symbiont of the stinkbug Plautia stali was replaced by E. coli, a few survivor insects exhibited specific localization and vertical transmission of E. coli. Through trans-generational maintenance with P. stali, several hyper-mutating E. coli lines independently evolved hosts high adult emergence and improved body color. Such "mutualistic" E. coli lines exhibited independent mutations disrupting the carbon catabolite repression (CCR) global transcriptional regulator. Each of the mutations reproduced the mutualistic phenotypes when introduced into wild-type E. coli, confirming that the single CCR mutations instantly make E. coli an insect mutualist. Our discovery uncovers that evolution of elaborate mutualism can proceed more easily and rapidly than conventionally envisaged.

evolutionary biology↗