Cytokinin-microbiome interactions regulate developmental functions

Background The interaction of plants with the complex microbial networks that inhabit them is important for plant health. While the reliance of plants on their microbial inhabitants for defense against invading pathogens is well documented, the acquisition of data concerning the relationships between plant developmental stage or aging, and microbiome assembly, is still underway. The plant hormone cytokinin (CK) regulates various plant growth and developmental processes. Here, examining the relationships between plant development and microbiome assembly, we observed developmental-age dependent changes in the phyllopshere microbiome. We show that age-related shifts in microbiome content vary based on content of, or sensitivity to, CK. Results We found a developmental age associated decline in microbial richness and diversity, accompanied by a decline in the presence of growth promoting and resistance inducing Bacilli in the phyllosphere. This decline was absent from CK-rich or CK-hypersensitive genotypes. Bacillus isolates we obtained from CK rich genotypes were found to alter the expression of developmental genes to support morphogenesis and alter the leaf developmental program when applied to seedlings, and enhance yield and agricultural productivity when applied to mature plants. Conclusions Our results support the notion that CK supports developmental functions in part via the bacterial community.

The Occurrence of Malignancy in Trypanosoma brucei brucei by Rapid Passage in Mice

Pleomorphic Trypanosoma brucei are best known for their tightly controlled cell growth and developmental program, which ensures their transmissibility and host fitness between the mammalian host and insect vector. However, after long-term adaptation in the laboratory or by natural evolution, monomorphic parasites can be derived. The origin of these monomorphic forms is currently unclear. Here, we produced a series of monomorphic trypanosome stocks by artificially syringe-passage in mice, creating snapshots of the transition from pleomorphism to monomorphism. We then compared these artificial monomorphic trypanosomes, alongside several naturally monomorphic T. evansi and T. equiperdum strains, with the pleomorphic T. brucei. In addition to failing to generate stumpy forms in animal bloodstream, we found that monomorphic trypanosomes from laboratory and nature exhibited distinct differentiation patterns, which are reflected by their distinct differentiation potential and transcriptional changes. Lab-adapted monomorphic trypanosomes could still be induced to differentiate, and showed only minor transcriptional differences to that of the pleomorphic slender forms but some accumulated differences were observed as the passages progress. All naturally monomorphic strains completely fail to differentiate, corresponding to their impaired differentiation regulation. We propose that the natural phenomenon of trypanosomal monomorphism is actually a malignant manifestation of protozoal cells. From a disease epidemiological and evolutionary perspective, our results provide evidence for a new way of thinking about the origin of these naturally monomorphic strains, the malignant evolution of trypanosomes may raise some concerns. Additionally, these monomorphic trypanosomes may reflect the quantitative and qualitative changes in the malignant evolution of T. brucei, suggesting that single-celled protozoa may also provide the most primitive model of cellular malignancy, which could be a primitive and inherent biological phenomenon of eukaryotic organisms from protozoans to mammals.

Recruitment of an ancient branching program to suppress carpel development in maize flowers

Carpels in maize undergo programmed cell death in half of the flowers initiated in ears and in all flowers in tassels. The HD-ZIP I transcription factor gene GRASSY TILLERS1 (GT1) is one of only a few genes known to regulate this process. To identify additional regulators of carpel suppression, we performed a gt1 enhancer screen and found a genetic interaction between gt1 and ramosa3 (ra3). RA3 is a classic inflorescence meristem determinacy gene that encodes a trehalose-6-phosphate (T6P) phosphatase (TPP). Dissection of floral development revealed that ra3 single mutants have partially derepressed carpels, whereas gt1;ra3 double mutants have completely derepressed carpels. Surprisingly, gt1 suppresses ra3 inflorescence branching, revealing a role for gt1 in meristem determinacy. Supporting these genetic interactions, GT1 and RA3 proteins colocalize to carpel nuclei in developing flowers. Global expression profiling revealed common genes misregulated in single and double mutant flowers, as well as in derepressed gt1 axillary meristems. Indeed, we found that ra3 enhances gt1 vegetative branching, similar to the roles for the trehalose pathway and GT1 homologs in the eudicots. This functional conservation over ∼160 million years of evolution reveals ancient roles for GT1-like genes and the trehalose pathway in regulating axillary meristem suppression, later recruited to mediate carpel suppression. Our findings expose hidden pleiotropy of classic maize genes and show how an ancient developmental program was redeployed to sculpt floral form.

The development of phrasal speech in primary schoolchildren with multiple developmental disabilities

Introduction. Today, the education system covers all categories of children with disabilities. This category also includes children with severe and multiple developmental disabilities. Until recently, only a small part of these children studied. Most of them did not study due to the severity of a developmental disability. Consequently, in order to exercise their constitutional right to education, specialists of a special (defectological) profile should be actively involved in the development of training programs and psychological-pedagogical support for such children. The purpose of the study is to test a program for phrasal speech development in primary schoolchildren with multiple developmental disabilities. Materials and methods. The study was conducted at schools for students with disabilities in the cities of Kirovo-Chepetsk and Kirov (Kirov region, Russian Federation). The empirical part of the work was carried out on a sample of thirty-four (34) primary schoolchildren with multiple developmental disabilities. The adapted methodology of L.V. Kovrigina "The study of phrasal speech" was used, which makes it possible to assess the development of impressive and expressive phrasal speech. Results. A correctional-developmental program for phrasal speech development in primary schoolchildren with multiple developmental disabilities was developed and tested. This program is aimed at developing the understanding of addressed speech, expanding vocabulary, activating one's own speech utterance through learning to form and expand a phrase. The positive dynamics of phrasal speech development in primary schoolchildren after the formative experiment was revealed. There were significant changes in the development of impressive (χ2=47.852 at p≤0.05) and expressive (χ2=33.78 at p≤0.05) phrasal speech. Discussion and conclusion. The research materials can be used by specialists in organizing and performing correctional-developmental work with this category of children in the context of special education.

Locomotion and searching behaviour in the honey bee larva depend on nursing interaction

Although honey bee brood does not need to seek shelter or food and restricts its movements to small wax cells, larvae have some degree of motility. Previously, other studies described how honey bee larvae showed analogous behaviours to the wandering period in holometabolous insects. The current research aimed to measure locomotion of the honey bee brood at different conditions of food supply and larval stadia. Besides, we developed an actometry assay to describe the larval behaviour under laboratory conditions. Our results suggested that the satiety and developmental program of larvae modulated their locomotion. Before they pupated, larval speed increased sharply and then it dropped until quiescence. However, starvation also induced an increase in angular velocity of brood. Starved larvae were between three and five times faster than the satiated ones. Moreover, fifth instars left their wax cells after 2 h of starvation without nurse bees. In the actometry assay, larvae showed behaviours of dispersion and changes in their kinematic parameters after detecting a tactile stimulus like the edge of arenas.

Transcriptomic and Genetic Analyses Identify the Krüppel-Like Factor Dar1 as a New Regulator of Tube-Shaped Long Tendon Development

To ensure locomotion and body stability, the active role of muscle contractions relies on a stereotyped muscle pattern set in place during development. This muscle patterning requires a precise assembly of the muscle fibers with the skeleton via a specialized connective tissue, the tendon. Like in vertebrate limbs, Drosophila leg muscles make connections with specific long tendons that extend through different segments. During the leg disc development, cell precursors of long tendons rearrange and collectively migrate to form a tube-shaped structure. A specific developmental program underlies this unique feature of tendon-like cells in the Drosophila model. We provide for the first time a transcriptomic profile of leg tendon precursors through fluorescence-based cell sorting. From promising candidates, we identified the Krüppel-like factor Dar1 as a critical actor of leg tendon development. Specifically expressed in the leg tendon precursors, loss of dar1 disrupts actin-rich filopodia formation and tendon elongation. Our findings show that Dar1 acts downstream of Stripe and is required to set up the correct number of tendon progenitors.

A Dual Role for Abscisic Acid Integrating the Cold Stress Response at the Whole-Plant Level in Iris pseudacorus L. Growing in a Natural Wetland

Leaf senescence, the last stage of the developmental program of leaves, can be induced by both internal and external signals. Cold stress-induced leaf senescence is an efficient strategy to overcome winter temperatures. In this work, we studied leaf senescence in yellow flag (Iris pseudacorus L.) individuals growing in a natural wetland, not only considering its relationship with external and internal cues, but also the plant developmental program, and the biological significance of rhizomes, storage organs that remain viable through winter. Total chlorophyll contents and the maximum efficiency of PSII (Fv/Fm ratio) decreased in senescing leaves, which was associated with a sharp increase in abscisic acid (ABA) contents. Furthermore, total cytokinin and 2-isopentenyladenine contents decreased in December compared to November, as plants became more stressed due to a decline in air temperatures. ABA increases in senescing leaves increased in parallel to reductions in violaxanthin. Rhizomes also accumulated large amounts of ABA during winter, while roots did not, and neither roots nor rhizomes accumulated 9-cis-epoxycarotenoids, thus suggesting ABA, which might play a role in conferring cold tolerance to this subterranean organ, may result from phloem transport from senescing leaves. It is concluded that (i) leaf senescence is a highly regulated physiological process in yellow flag playing a key role in the modulation of the entire plant developmental program, and (ii) ABA plays a major role not only in the regulation of leaf senescence but also in the establishment of cold tolerance in rhizomes, two processes that appear to be intimately interconnected.

Intellectual Readiness for School in Senior Preschoolers: case of Correctional and Developmental Program "School is Waiting"

Cognitive readiness is a level of cognitive skills sufficient for systematic learning. It includes cognitive processes (perception, memory, thinking, imagination, and speech), knowledge, skills, motivation, etc. The research featured cognitive readiness for primary school in senior preschoolers after a special correction and development program "School is Waiting", which was based on a series of games. The program proved to be highly effective as tested by L. S. Kolmogorova’s diagnostic program "Readiness for School". Children in the test group received a higher total score for knowledge, long-term memory, auditory perception, speech, imagination, etc. than those in the control group.

Designing a Genetic Screen to Identify Factors Required for Meiotic Nuclear Rejuvenation

During the natural cycle of life, most eukaryotic organisms grow old, age, and die. A common natural mechanism by which organisms “reset” their lifespan is through sexual reproduction; however, how this rejuvenation takes place remains unknown. My lab has found that meiosis in budding yeast, the developmental program that forms sex cells, eliminates age-induced damage. This involves the formation of a novel nuclear compartment, the Gametogenesis Uninherited Nuclear Compartment (GUNC), which acts as a trash can for accumulated age-induced damage. To understand the molecular details of this process, I worked on designing a screen for genes involved in GUNC formation. My mentor and I fused three different proteins targeted to the GUNC and a protein that is able to bind to a drug-resistance plasmid, in order to couple the inheritance of a selectable DNA marker with the elimination of age-induced damage. Initial testing of these three fusion proteins suggested that they were unable to successfully target the plasmid to the GUNC; as such, testing of additional candidate proteins is necessary. We plan to eventually use this system to identify mutations that disrupt GUNC formation and cause inheritance of the drug-resistance plasmid. By identifying and perturbing proteins involved in GUNC formation, we are hoping to be able to drive the inheritance of specific types of age-induced damage, allowing for the determination of what a symptom versus a cause of aging is.