Abscisic Acid: A Potential Secreted Effector Synthesized by Phytophagous Insects for Host-Plant Manipulation.

Abscisic acid (ABA) is an isoprenoid-derived plant signaling molecule involved in a wide variety of plant processes, including facets of growth and development as well as responses to abiotic and biotic stress. ABA had previously been reported in a wide variety of animals, including insects and humans. We used high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-(ESI)-MS/MS) to examine concentrations of ABA in 17 species of phytophagous insects, including gall- and non-gall-inducing species from all insect orders with species known to induce plant galls: Thysanoptera, Hemiptera, Lepidoptera, Coleoptera, Diptera, and Hymenoptera. We found ABA in insect species in all six orders, in both gall-inducing and non-gall-inducing species, with no tendency for gall-inducing insects to have higher concentrations. The concentrations of ABA in insects often markedly exceeded those typically found in plants, suggesting it is highly improbable that insects obtain all their ABA from their host plant via consumption and sequestration. As a follow-up, we used immunohistochemistry to determine that ABA localizes to the salivary glands in the larvae of the gall-inducing Eurosta solidaginis (Diptera: Tephritidae). The high concentrations of ABA, combined with its localization to salivary glands, suggest that insects are synthesizing and secreting ABA to manipulate their host plants. The pervasiveness of ABA among both gall- and non-gall-inducing insects and our current knowledge of the role of ABA in plant processes suggest that insects are using ABA to manipulate source-sink mechanisms of nutrient allocation or to suppress host-plant defenses. ABA joins the triumvirate of phytohormones, along with cytokinins (CKs) and indole-3-acetic acid (IAA), that are abundant, widespread, and localized to glandular organs in insects and used to manipulate host plants.

Formant Tuning and Feedback in the Male Passaggio.

It has been suggested that traversing the male (secondo) passaggio requires two important adjustments. When singing up the scale, first of all, the second harmonic (H2) needs to pass over the first formant (F1). After that, the timbre of the voice takes on a different, slightly "darker" quality. This is the pitch where, in singers' jargon, the voice reaches secondo passaggio. Above secondo passaggio, in the optimal arrangement, the second formant (F2) is tuned close to one of the higher harmonics, or, sometimes alternatively, the singer's formant cluster induces a dominant resonance in the approximate range of 2.4-3.4 kHz. These two adjustments together produce the typical sound of the classical male upper voice. In this study, we have investigated the choices individual singers make while negotiating the passaggio and the effect of feedback from the vocal tract to the voice source during this maneuver. Electroglottograph (EGG) and microphone signals were recorded of nine male singers (five tenors and four baritones) using VoceVista. Inverse filtering was performed on the microphone signals, using the Sopran/DeCap application, to reveal the shape of the glottal airflow pulses.

The contribution of seed dispersers to tree species diversity in tropical rainforests.

Tropical rainforests are known for their extreme biodiversity, posing a challenging problem in tropical ecology. Many hypotheses have been proposed to explain the diversity of tree species, yet our understanding of this phenomenon remains incomplete. Here, we consider the contribution of animal seed dispersers to the species diversity of trees. We built a multi-layer lattice model of trees whose animal seed dispersers are allowed to move only in restricted areas to disperse the tree seeds. We incorporated the effects of seed dispersers in the traditional theory of allopatric speciation on a geological time scale. We modified the lattice model to explicitly examine the coexistence of new tree species and the resulting high biodiversity. The results indicate that both the coexistence and diversified evolution of tree species can be explained by the introduction of animal seed dispersers.

The origin and genetic differentiation of the socially parasitic aphid Tamalia inquilinus.

Social and brood parasitisms are nonconsumptive forms of parasitism involving the exploitation of the colonies or nests of a host. Such parasites are often related to their hosts and may evolve in various ecological contexts, causing evolutionary constraints and opportunities for both parasites and their hosts. In extreme cases, patterns of diversification between social parasites and their hosts can be coupled, such that diversity of one is correlated with or even shapes the diversity of the other. Aphids in the genus Tamalia induce galls on North American manzanita (Arctostaphylos) and related shrubs (Arbutoideae) and are parasitized by nongalling social parasites or inquilines in the same genus. We used RNA sequencing to identify and generate new gene sequences for Tamalia and performed maximum-likelihood, Bayesian and phylogeographic analyses to reconstruct the origins and patterns of diversity and host-associated differentiation in the genus. Our results indicate that the Tamalia inquilines are monophyletic and closely related to their gall-forming hosts on Arctostaphylos, supporting a previously proposed scenario for origins of these parasitic aphids. Unexpectedly, population structure and host-plant-associated differentiation were greater in the non-gall-inducing parasites than in their gall-inducing hosts. RNA-seq indicated contrasting patterns of gene expression between host aphids and parasites, and perhaps functional differences in host-plant relationships. Our results suggest a mode of speciation in which host plants drive within-guild diversification in insect hosts and their parasites. Shared host plants may be sufficient to promote the ecological diversification of a network of phytophagous insects and their parasites, as exemplified by Tamalia aphids.

Fine-tuned bee-flower coevolutionary state hidden within multiple pollination interactions.

Relationships between flowers and pollinators are generally considered cases of mutualism since both agents gain benefits. Fine-tuned adaptations are usually found in the form of strict one-to-one coevolution between species. Many insect pollinators are, however, considered generalists, visiting numerous kinds of flowers, and many flower species (angiosperms) are also considered generalists, visited by many insect pollinators. We here describe a fine-tuned coevolutionary state of a flower-visiting bee that collects both nectar and pollen from an early spring flower visited by multiple pollinators. Detailed morphology of the bee proboscis is shown to be finely adjusted to the floral morphology and nectar production of the flower. Behavioral observations also confirm the precision of this mutualism. Our results suggest that a fine-tuned one-to-one coevolutionary state between a flower species and a pollinator species might be common, but frequently overlooked, in multiple flower-pollinator interactions.

Quaternary diffusion coefficients in a protein-polymer-salt-water system determined by rayleigh interferometry.

We have experimentally investigated multicomponent diffusion in a protein-polymer-salt-water quaternary system. Specifically, we have measured the nine multicomponent diffusion coefficients, D(ij), for the lysozyme-poly(ethylene glycol)-NaCl-water system at pH 4.5 and 25 degrees C using precision Rayleigh interferometry. Lysozyme is a model protein for protein-crystallization and enzymology studies. We find that the protein diffusion coefficient, D(11), decreases as polymer concentration increases at a given salt concentration. This behavior can be quantitatively related to the corresponding increase in fluid viscosity only at low polymer concentration. However, at high polymer concentration (250 g/L), protein diffusion is enhanced compared to the corresponding viscosity prediction. We also find that a protein concentration gradient induces salt diffusion from high to low protein concentration. This effect increases in the presence of poly(ethylene glycol). Finally, we have evaluated systematic errors associated with measurements of protein diffusion coefficients by dynamic light scattering. This work overall helps characterize protein diffusion in crowded environments and may provide guidance for further theoretical developments in the field of protein crystallization and protein diffusion in such crowded systems, such as the cytoplasm of living cells.

The effect of salt on protein chemical potential determined by ternary diffusion in aqueous solutions.

We use accurate thermodynamic derivatives extracted from high-precision measurements of the four volume-fixed diffusion coefficients in ternary solutions of lysozyme chloride in aqueous NaCl, NH4Cl, and KCl at pH 4.5 and 25 degrees C to (a) assess the relative contributions of the common-ion and nonideality effects to the protein chemical potential as a function of salt concentration, (b) compare the behavior of the protein chemical potential for the three salts, which we found to be consistent with the Hofmeister series, and (c) discuss our thermodynamic data in relation to the dependence of the protein solubility on salt concentration. The four diffusion coefficients are reported at 0.6 mM lysozyme chloride and 0.25, 0.5, 0.9, 1.2, and 1.5 M KCl and extend into the protein-supersaturated region. The chemical potential cross-derivatives are extracted from diffusion data using the Onsager reciprocal relation and the equality of molal cross-derivatives of solute chemical potentials. They are compared to those calculated previously from diffusion data for lysozyme in aqueous NaCl and NH4Cl. We estimate the effective charge on the diffusing lysozyme cation at the experimental concentrations. Our diffusion measurements on the three salts allowed us to analyze and interpret the four diffusion coefficients for charged proteins in the presence of 1:1 electrolytes. Our results may provide guidance to the understanding of protein crystallization.

'Mixing' the registers: glottal source or vocal tract?

Electroglottograph and microphone signals are examined of scale passages crossing the boundary between chest and middle registers in the female singing voice. From a protocol executed by professional classical singers, the examples are selected to illustrate differing approaches to the chest-middle transition, as well as to illuminate varying theories on the female middle register, specifically the question of 'mixing' the primary registers, chest and falsetto. The results suggest that the skillful tuning of the resonances of the vocal tract contributes more toward the pedagogical goal of smoothing the register transition than does a presumed mixing of the registers at the glottal source.

Resonance strategies revealed in recorded tenor high notes.

With careers that depend to a large extent on the amplitude and sonorous beauty of their voices, opera singers must pay special attention to high notes, where the wide spacing of the harmonics of the voice source intensifies the critical importance of the tuning of the resonances of the vocal tract. This study uses spectrum analysis to examine a large number of recordings of a particularly challenging high note for tenors, the final sustained B4-flat of the aria 'Celeste Aida' from Verdi's opera Aida. The resonance strategy most frequently found uses a markedly displaced second formant to create a dominant resonance at the frequency of the third harmonic, about 1,400 Hz. Other strategies and combinations of strategies are examined as well. Arguments concerning the validity of drawing conclusions from the acoustic signals available in commercial recordings are considered, and it is concluded that such recordings can contain valuable information on resonance strategies for those who aspire to sing similar high notes.

A new method to record subglottal pressure waves: potential applications.

Rapid subglottal pressure changes related to the glottal cycles influence the aerodynamics of phonation. Various methods to measure these have been developed, but are not practical for routine phoniatric use. For that reason, a noninvasive measurement tool is necessary. This article presents a technique that uses a microphone positioned at the skin of the jugular fossa to record the signal which arises in the subglottal spaces and is transmitted through the soft tissue to the surface of the skin. Using the program Glottal Segmentation of Voice and Speech, jugular microphone recordings from two healthy subjects were compared with simultaneously recorded direct intratracheal measurements during the same phonation. A systematic error arising from the transmission properties of the microphone and the soft tissue leads to phase and amplitude deviations. These must be taken into account and require correction. This correction procedure leads to high correlations and a good agreement between the two signals. Even without this correction the jugular microphone measurements proved to be useful as a diagnostic and a therapeutic tool in cases where chest resonance specific processes appear affected. In addition, they offer material for research purposes. Although based on a small number of subjects, the new method shows a good validity; testing on a larger number of subjects will probably strengthen the validity.

Change in singing voice production, objectively measured.

Although subglottal pressures in conversational speech are relatively easily measured and thus known, the higher values that sometimes occur in singing (especially in tenors) have received little attention in the literature. Still more unusual is the opportunity to measure a large-scale change over decades in the application of pressure in singing production. This study compares measurements of subglottal pressure in a tenor/singing teacher (JS) at two points in his career: in his early thirties, when he was a subject in HS's dissertation study on the efficiency of voice production; and recently, in his fifties, in connection with JS's forthcoming book on the history of the pedagogy of Bel Canto. Although a single case study, its points of special interest include the high values initially measured (up to 100 cm H2O) and the reduction of this figure by more than 50% in the maximal values of the recent measurements. The study compares these values with those of other singers in the same laboratory (both with esophageal balloon and directly, with a catheter passed through the glottis) and in the literature, as well as discusses in detail the problems pertaining to the measurement (repeatability, correcting for lung volume, etc.). As a sophisticated subject, JS makes some pertinent observations about the changes in his use of subglottal pressure.

Measurement of characteristic leap interval between chest and falsetto registers.

A markedly smaller time constant distinguishes a chest-falsetto leap from the more usual execution of a sung interval by muscular adjustments in the length and tension of the vocal folds. The features of such a chest-falsetto leap are examined in detail with respect to F0, peak-to-peak amplitude of the vocal-fold contact area signal (EGG), and the closed quotient. A method is proposed to standardize and quantify this chest-falsetto leap in the characteristic leap interval (CLI), a measure of the separation between the natural registers in a given singing voice. The measure is applied to a varied group of experienced singers. Preliminary results include a suggested dimorphic pattern with respect to sex, with female voices exhibiting smaller CLIs and less individual diversity than male voices.