Structural mechanism of JH delivery in hemolymph by JHBP of silkworm, Bombyx mori

Juvenile hormone (JH) plays crucial roles in many aspects of the insect life. All the JH actions are initiated by transport of JH in the hemolymph as a complex with JH-binding protein (JHBP) to target tissues. Here, we report structural mechanism of JH delivery by JHBP based upon the crystal and solution structures of apo and JH-bound JHBP. In solution, apo-JHBP exists in equilibrium of multiple conformations with different orientations of the gate helix for the hormone-binding pocket ranging from closed to open forms. JH-binding to the gate-open form results in the fully closed JHBP-JH complex structure where the bound JH is completely buried inside the protein. JH-bound JHBP opens the gate helix to release the bound hormone likely by sensing the less polar environment at the membrane surface of target cells. This is the first report that provides structural insight into JH signaling

Induction of vacuolar invertase inhibitor mRNA in potato tubers contributes to cold-induced sweetening resistance and includes spliced hybrid mRNA variants

Cold storage of tubers of potato (Solanum tuberosum L.) compromises tuber quality in many cultivars by the accumulation of hexose sugars in a process called cold-induced sweetening. This is caused by the breakdown of starch to sucrose, which is cleaved to glucose and fructose by vacuolar acid invertase. During processing of affected tubers, the high temperatures involved in baking and frying cause the Maillard reaction between reducing sugars and free amino acids, resulting in the accumulation of acrylamide. cDNA clones with deduced proteins homologous to known invertase inhibitors were isolated and the two most abundant forms, termed INH1 and INH2, were shown to possess apoplastic and vacuolar localization, respectively. The INH2 gene showed developmentally regulated alternative splicing, so, in addition to the INH2α transcript encoding the full-length protein, two hybrid mRNAs (INH2β*A and INH2β*B) that encoded deduced vacuolar invertase inhibitors with divergent C-termini were detected, the result of mRNA splicing of an upstream region of INH2 to a downstream region of INH1. Hybrid RNAs are common in animals, where they may add to the diversity of the proteome, but are rarely described in plants. During cold storage, INH2α and the hybrid INH2β mRNAs accumulated to higher abundance in cultivars resistant to cold-induced sweetening than in susceptible cultivars. Increased amounts of invertase inhibitor may contribute to the suppression of acid invertase activity and prevent cleavage of sucrose. Evidence for increased RNA splicing activity was detected in several resistant lines, a mechanism that in some circumstances may generate a range of proteins with additional functional capacity to aid adaptability

The various and varying roles of specific chaperones in type III secretion systems

The type III secretion pathway is used by numerous Gram-negative pathogenic bacteria to deliver proteins within the membrane or the cytoplasm of eukaryotic cells with which these bacteria interact. Secretion is regulated by external signals. This requires that, before being secreted, proteins are stored in the cytoplasm where they need to be stabilised, separated from other interaction partners, and maintained in a secretion-competent state. Specialised, energy-independent chaperones play various roles in these functions by associating in the cytoplasm with proteins before their secretion. Some chaperones are also directly involved in modulating transcription in response to secretion

Characterization of Actinidia virus 1, a new member of the family Closteroviridae encoding a thaumatin-like protein

A new member of the family Closteroviridae was detected in Actinidia chinensis grown in Italy, using next generation sequencing of double-stranded RNA. The virus isolate, named Actinidia virus 1 (AcV-1) has a genome of 18,848\uc2 nts in length, a structure similar to the unclassified persimmon virus B (PeVB) and contains 12 open reading frames (ORFs) greater than 6\uc2 KDa, one carrying two papain-like leader proteases, a methyltransferase, a helicase and an RNA-dependent RNA polymerase domain. Additional ORFs code for homologs of heat shock protein 70, heat shock protein 90 and a coat protein. Curiously, AcV-1 and PeVB genomes code for a thaumatin-like protein, a peculiarity unreported for other viruses. In phylogenetic analyses both viruses group in a distinct clade evolutionarily related to closteroviruses. The final taxonomic position of AcV-1 within the family Closteroviridae is yet to be clarified