Biology subjects

Mizoguchi, A.

Publications and source records attributed to Mizoguchi, A..

4 recordsLinked to original sources

bioRxiv2022

Female reproductive dormancy in Drosophila melanogaster is regulated by DH31-producing neurons projecting into the corpus allatum

Female reproductive dormancy in insects is a process that drastically suppresses oogenesis to conserve energy under adverse environments. In many insects, including the fruit fly, Drosophila melanogaster, reproductive dormancy is induced under low-temperature and short-day conditions by the downregulation of juvenile hormone (JH) biosynthesis by the corpus allatum (CA). Previous studies have suggested that brain neurons that project directly to the CA are important for the regulation of reproductive dormancy. However, the role of CA-projecting neurons in JH-mediated reproductive dormancy has not yet been confirmed by molecular genetic studies. In this study, we report that, in adult D. melanogaster, the neuropeptide diuretic hormone 31 (DH31) is produced by brain neurons that project into the CA. DH31-producing-CA-projecting neurons are connected downstream with a subset of circadian clock neurons, such as s-LNvs, which are known to be involved in reproductive dormancy regulation. The CA expresses the gene encoding the DH31 receptor, which is required for DH31-triggered elevation of intracellular cAMP in the CA. Knocking down Dh31 in these CA-projecting neurons or DH31 receptor in the CA leads to a failure in the decrease of the JH titer, normally observed under dormancy-inducing conditions, leading to abnormal yolk accumulation in the ovaries. Our findings provide the first molecular genetic evidence demonstrating that CA-projecting peptidergic neurons play an essential role in regulating reproductive dormancy by suppressing JH biosynthesis. Significance StatementDormancy is an adaptive physiological response to environmental changes that are unsuitable for survival. Adult females of many insect species undergo reproductive dormancy in which oogenesis is drastically arrested; it is induced by a decrease in juvenile hormone (JH) titers. However, we are yet to fully understand the molecular mechanisms underlying the control of JH biosynthesis under dormancy-inducing conditions. In this study using the fruit fly, we demonstrated that brain neurons projecting directly to the JH-producing organ, corpus allatum, play an essential role in regulating reproductive dormancy via the neuropeptide DH31. As the morphologically-similar neurons have previously been suggested to be involved in reproductive dormancy regulation, this study provides a fundamental molecular and neuronal basis for reproductive dormancy in insects.

physiology↗

bioRxiv2021

Asymmetric Structure of the Native Rhodobacter sphaeroides Dimeric LH1-RC Complex

The light-harvesting-reaction center (LH1-RC) core complex of purple photosynthetic bacterium Rhodobacter (Rba.) sphaeroides is characterized by the presence of both a dimeric form and a monomeric form. Following structure determination of the monomeric LH1-RC including its previously unrecognized component designated protein-U (Nat. Commun. 12, 6300, 2021), here we present cryo-EM structures of the dimeric LH1-RC from native Rba. sphaeroides IL106 at 2.75 [A] resolution and from an LH1-RC monomer lacking protein-U ({Delta}U) at 2.64 [A] resolution. The native dimeric core complex reveals many asymmetric features in the arrangement of its two monomeric components including the structural integrity of protein-U, the overall LH1 organization, and the rigidities of the proteins and pigments that form the complex. PufX polypeptides play a critical role in connecting two monomers, with one PufX interacting at its N-terminus with another PufX and an LH1 {beta}-polypeptide in another monomer, in good agreement with biochemical analyses. One of the proteins-U was only partially identified in the dimeric structure, signaling significantly different degrees of disorder in the two monomers. The {Delta}U LH1-RC monomer revealed a half-moon-shaped structure containing 11 - and 10 {beta}-polypeptides (compared with 14 of each in the wild type), indicating a critical role for protein-U in controlling the number of {beta}-subunits required for correct assembly and stabilization of the LH1-RC dimer. The structural features are discussed in relation to the unusual topology of intracytoplasmic photosynthetic membranes and an assembly model proposed for the native Rba. sphaeroides dimeric LH1-RC complex in membranes of wild-type cells.

biochemistry↗

bioRxiv2021

A Novel Membrane Protein in the Rhodobacter sphaeroides LH1-RC Photocomplex

We present a cryo-EM structure of the monomeric light-harvesting-reaction center (LH1-RC) core complex from photosynthetic purple bacterium Rhodobacter (Rba.) sphaeroides at 2.9 [A] resolution. The LH1 complex forms a C-shaped structure composed of 14 {beta}-polypeptides around the RC with a large ring opening. From the cryo-EM density map, a previously unrecognized integral membrane protein, referred to as protein-U, was identified. Protein-U has a U-shaped conformation near the LH1-ring opening and was annotated as a hypothetical protein in the Rba. sphaeroides genome. Deletion of protein-U resulted in a mutant strain that expressed a much-reduced amount of the dimeric LH1-RC, indicating an important role for protein-U in dimerization of the LH1-RC complex. PufX was located opposite protein-U on the LH1-ring opening, and both its position and conformation differed from that of previous reports of dimeric LH1-RC structures obtained at low-resolution. Twenty-six molecules of the carotenoid spheroidene arranged in two distinct configurations were resolved in the Rba. sphaeroides LH1 and were positioned within the complex to block its pores. Our findings offer a new view of the core photocomplex of Rba. sphaeroides and the connections between structure and function in bacterial photocomplexes in general.

biochemistry↗

bioRxiv2021

Cryo-EM Structure of the Photosynthetic LH1-RC Complex from Rhodospirillum rubrum

We present a cryo-EM structure of the light-harvesting-reaction center (LH1-RC) core complex from purple phototrophic bacterium Rhodospirillum (Rsp.) rubrum at 2.76 [A] resolution. The LH1 complex forms a closed, slightly elliptical ring structure with 16 {beta}-polypeptides surrounding the RC. Our biochemical analysis detected rhodoquinone (RQ) molecules in the purified LH1-RC, and the cryo-EM density map specifically positions RQ at the QA site in the RC. The geranylgeraniol sidechains of bacteriochlorophyll (BChl) aG coordinated by LH1 {beta}-polypeptides exhibit a highly homologous tail-up conformation that allows for interactions with the bacteriochlorin rings of nearby LH1 -associated BChls aG. The structure also revealed key protein-protein interactions in both N- and C-terminal regions of the LH1 {beta}-polypeptides, mainly within a face-to-face structural subunit. Our findings enable to evaluate past experimental and computational results obtained with this widely used organism and provide crucial information for more detailed exploration of light-energy conversion, quinone transport, and structure-function relationships in pigment-protein complexes.

biochemistry↗