In vitro reconstitution of active ribulose bisphosphate carboxylase (Rubisco) from unfolded polypeptides is facilitated by the molecular chaperones: chaperonin-60 from Escherichia coli (groEL), yeast mitochondria (hsp60) or chloroplasts (Rubisco sub-unit-binding protein), together with chaperonin-10 from E. coli (groES), and Mg-ATP. Because chaperonins are ubiquitous, a conserved Mg-ATP-dependent mechanism exists that uses the chaperonins to facilitate the folding of some other proteins.

Background Helicoverpa armigera and Helicoverpa zea are major caterpillar pests of Old and New World agriculture, respectively. Both, particularly H. armigera, are extremely polyphagous, and H. armigera has developed resistance to many insecticides. Here we use comparative genomics, transcriptomics and resequencing to elucidate the genetic basis for their properties as pests.ResultsWe find that, prior to their divergence about 1.5 Mya, the H. armigera/H. zea lineage had accumulated up to more than 100 more members of specific detoxification and digestion gene families and more than 100 extra gustatory receptor genes, compared to other lepidopterans with narrower host ranges. The two genomes remain very similar in gene content and order, but H. armigera is more polymorphic overall, and H. zea has lost several detoxification genes, as well as about 50 gustatory receptor genes. It also lacks certain genes and alleles conferring insecticide resistance found in H. armigera. Non-synonymous sites in the expanded gene families above are rapidly diverging, both between paralogues and between orthologues in the two species. Whole genome transcriptomic analyses of H. armigera larvae show widely divergent responses to different host plants, including responses among many of the duplicated detoxification and digestion genes.ConclusionsThe extreme polyphagy of the two heliothines is associated with extensive amplification and neofunctionalisation of genes involved in host finding and use, coupled with versatile transcriptional responses on different hosts. H. armigera’s invasion of the Americas in recent years means that hybridisation could generate populations that are both locally adapted and insecticide resistant.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-017-0402-6) contains supplementary material, which is available to authorized users.

Further evidence for time-dependent interconversions between active and inactive states of ribulose 1,5-bisphosphate carboxylase is presented. It was found that ribulose bisphosphate oxygenase and ribulose bisphosphate carboxylase could be totally inactivated by excluding CO2 and Mg2+ during dialysis of the enzyme at 4 degrees C. When initially inactive enzyme was assayed, the rate of reaction continually increased with time, and the rate was inversely related to the ribulose bisphosphare concentration. The initial rate of fully activated enzyme showed normal Michaelis-Menten kinetics with respect to ribulose bisphosphate (Km = 10muM). Activation was shown to depend on both CO2 and Mg2+ concentrations, with equilibrium constants for activation of about 100muM and 1 mM respectively. In contrast with activation, catalysis appeared to be independent of Mg2+ concentration, but dependent on CO2 concentration, with a Km(CO2) of about 10muM. By studying activation and de-activation of ribulose bisphosphate carboxylase as a function of CO2 and Mg2+ concentrations, the values of the kinetic constants for these actions have been determined. We propose a model for activation and catalysis of ribulose bisphosphate carboxylase: (see book) where E represents free inactive enzyme; complex in parentheses, activated enzyme; R, ribulose bisphosphate; M, Mg2+; C, CO2; P, the product. We propose that ribulose bisphosphate can bind to both the active and inactive forms of the enzyme, and slow inter-conversion between the two states occurs.

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Plants defend against attack from herbivores by direct and indirect defence mechanisms mediated by the accumulation of phytoalexins and release of volatile signals, respectively. While the defensive arsenals of some plants, such as tobacco and Arabidopsis are well known, most of rice's (Oryza sativa) defence metabolites and their effectiveness against herbivores remain uncharacterized. Here, we used a non-biassed metabolomics approach to identify many novel herbivory-regulated metabolic signatures in rice. Most were up-regulated by herbivore attack while only a few were suppressed. Two of the most prominent up-regulated signatures were characterized as phenolamides (PAs), p-coumaroylputrescine and feruloylputrescine. PAs accumulated in response to attack by both chewing insects, i.e. feeding of the lawn armyworm (Spodoptera mauritia) and the rice skipper (Parnara guttata) larvae, and the attack of the sucking insect, the brown planthopper (Nilaparvata lugens, BPH). In bioassays, BPH insects feeding on 15% sugar solution containing p-coumaroylputrescine or feruloylputrescine, at concentrations similar to those elicited by heavy BPH attack in rice, had a higher mortality compared to those feeding on sugar diet alone. Our results highlight PAs as a rapidly expanding new group of plant defence metabolites that are elicited by herbivore attack, and deter herbivores in rice and other plants.

Proteinase inhibitors are a diverse group of proteins that share not only a common biochemical activity, but also the distinguishing feature of rapidly undergoing evolutionary variation. Currently, 59 distinct families of proteinase inhibitors have been recognized [1]. I use the term 'family' in this review to denote these phylogenetic groupings and the term 'class' to denote inhibitors that interact with proteinases with mechanistic similarities, i.e. the serine-, cysteine-, aspartic and metallo-proteinases. Phylogenetic relationships among several of these inhibitor families have been analysed: including the serpin family [2-8], Bowman-Birk [9,10], cereal trypsin ⁄ a-amylase inhibitor [11], proteinase inhibitor I [12], proteinase inhibitor II [13] and cystatin [14,15]. Compared with the total number of families that are currently recognized, this represents a very small proportion, although phylogenetic trees for all families have been constructed (http://merops.sanger. ac.uk). These relationships are useful in developing an understanding of when and where the inhibitor class evolved; however, they do not provide information on the mechanisms driving gene evolution.The focus of many reviews of proteinase inhibitors over the last 25 years has been on classification and structure-function relationships. These proteins have not been well recognized as a class of proteins with an interesting evolutionary history. The purpose of this review is to summarize, for the first time, information relevant to proteinase inhibitor evolution, much of it collected incidentally, with the express intention of stimulating possible interest in this area.Proteinase inhibitors and their binding to proteinases have been extremely well characterized for more than 70 years and I focus only on those inhibitors that have The interaction of proteinase inhibitors produced, in most cases, by host organisms and the invasive proteinases of pathogens or parasites or the dietary proteinases of predators, results in an evolutionary 'arms race' of rapid and ongoing change in both interacting proteins. The importance of these interactions in pathogenicity and predation is indicated by the high level and diversity of observable evolutionary activity that has been found. At the initial level of evolutionary change, recruitment of other functional protein-folding families has occurred, with the more recent evolution of one class of proteinase inhibitor from another, using the same mechanism and proteinase contact residues. The combination of different inhibitor domains into a single molecule is also observed. The basis from which variation is possible is shown by the high rate of retention of gene duplication events and by the associated process of inhibitory domain multiplication. At this level of reorganization, mutually exclusive splicing is also observed. Finally, the major mechanism by which variation is achieved rapidly is hypervariation of contact residues, an almost ubiquitous feature of proteinase inhibitors. The diversity of evolutionary me...

The endoplasmic reticulum (ER) body is an ER-related organelle that accumulates high levels of PYK10, a beta-glucosidase with an ER retention signal. Constitutive ER bodies are present in the epidermal cells of cotyledons, hypocotyls and roots of young Arabidopsis seedlings, but absent in rosette leaves. When leaves are wounded, ER bodies are induced around the wounding site of the leaves (inducible ER bodies). To clarify the functional differences between these two ER bodies, we compared constitutive ER bodies with inducible ER bodies in wounded cotyledons of Arabidopsis seedlings. We found that the number of ER bodies increased both in cotyledons wounded directly (locally wounded cotyledons) and in unwounded cotyledons exposed to the systemic wound response (systemically wounded cotyledons). Quantitative reverse transcription-PCR and immunoblot analyses revealed that BGLU18, encoding another beta-glucosidase with an ER retention signal, was induced at the site of wounding, whereas PYK10 was not. Immunocytochemical analysis showed that BGLU18 protein was exclusively localized in ER bodies formed directly at the wounding site on cotyledons. ER bodies were not induced in locally and systemically wounded cotyledons of the bglu18 knock-out mutant. These results indicate that constitutive and inducible ER bodies accumulate different sets of beta -glucosidases and may have distinct functions in defense responses.

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