Biology subjects

Luna, M.

Publications and source records attributed to Luna, M..

4 recordsLinked to original sources

bioRxiv2025

'Candidatus Phytoplasma zeae': community-driven delineation of the maize bushy stunt phytoplasma, a Dalbulus-transmitted corn pathogen confined to the Americas

A novel phytoplasma species, Candidatus Phytoplasma zeae, is proposed based on ecological distinctiveness, vector specificity, whole-genome comparisons, and community consensus. This phytoplasma is associated with maize bushy stunt (MBS) disease in corn (Zea mays) and is transmitted exclusively by Dalbulus maidis and D. elimatus, two leafhopper species endemic to the Americas, and has been reported in Brazil, Colombia, Mexico, Peru, and several U.S. states. Here we sequenced and assembled the genome of MBS phytoplasma strains from Brazil, and U.S. to describe and propose this new species. Although the 16S rRNA gene sequence of the proposed reference strain, MBSP-BRRS, shares >99% identity with that of Ca. Phytoplasma asteris, key nucleotide polymorphisms distinguish Ca. P. zeae from other 16SrI-related phytoplasma species. Average nucleotide identity (ANI) and average amino acid identity (AAI) values between Ca. P. zeae and Ca. P. asteris are 97.70-98.00% and 96.65-96.88%, respectively, both near the established species delineation thresholds. Comparative genomic analyses revealed unique gene clusters in Ca. P. zeae associated with amino acid transport, defense mechanisms, and protein turnover, which may contribute to its specialization in corn. The ecological profile of Ca. P. zeae, including its narrow host range and restricted geographic distribution, supports its recognition as a novel species under Rule c of the IRPCM guidelines. The designation Candidatus Phytoplasma zeae is therefore proposed by members of the research community who have studied this pathogen for over a decade, with the MBSP-BrazilRS strain serving as the reference.

microbiology↗

bioRxiv2021

Interoceptive perception of optogenetic brain stimulation

How do animals experience brain manipulations? Optogenetics has allowed us to manipulate selectively and interrogate neural circuits underlying brain function in health and disease. However, it is currently unknown whether mice could perceive arbitrary optogenetic stimulation in addition to their evoked physiological functions. To address this issue, mice were trained to report an optogenetic stimulation as a cue to obtain rewards and avoid punishments. It was found that mice could perceive optogenetic manipulations regardless of the brain area modulated, their rewarding effects, or the stimulation of glutamatergic, GABAergic, and dopaminergic cell types. We named this phenomenon optoception. Using optoception, mice could learn to execute two different sets of instructions based on the laser frequency. Importantly, optoception can occur either activating or silencing a single cell type. Our findings revealed that mices brains are capable of "monitoring" their self-activity, albeit indirectly, perhaps via interoception or as a discriminative stimulus, opening a new way to introduce information to the brain and control brain-computer interfaces.

neuroscience↗

bioRxiv2020

Lateral Hypothalamic GABAergic neurons encode and potentiate sucrose palatability

Sucrose is attractive to most species in the animal kingdom, not only because it induces a sweet taste sensation but also for its positive palatability (i.e., oromotor responses elicited by increasing sucrose concentrations). Although palatability is such an important sensory attribute, it is currently unknown which cell types encode and modulate sucroses palatability. Studies in mice have shown that activation of GABAergic LHAVgat+ neurons evokes voracious eating; however, it is not known whether these neurons would be driving consumption by increasing palatability. Using optrode recordings, we measured sucroses palatability while VGAT-ChR2 transgenic mice performed a brief access sucrose test. We found a subpopulation of LHAVgat+ neurons encodes palatability by increasing (or decreasing) their activity as a function of the increment in licking responses evoked by sucrose concentrations. Optogenetic gain of function experiments, where mice were able to choose among available water, 3%, or 18% sucrose solution, uncovered that opto-stimulation of LHAVgat+ neurons consistently promoted higher intake of the most palatable stimulus (18% sucrose). In contrast, if they self-stimulated near the less palatable stimulus, some VGAT-ChR2 mice preferred water over 18% sucrose. Unexpectedly, activation of LHAVgat+ neurons increased quinine intake but only during water deprivation, since in sated animals, they failed to promote quinine intake or tolerate an aversive stimulus. Conversely, these neurons promoted overconsumption of sucrose when it was the nearest stimulus. Also, experiments with solid foods further confirmed that these neurons increased food interaction time with the most palatable food available. We conclude that LHAVgat+ neurons increase the drive to consume, but it is potentiated by the palatability and proximity of the tastant.

neuroscience↗

bioRxiv2018

Bone-Inspired Microarchitectured Materials with Enhanced Fatigue Life

Microarchitectured materials achieve superior mechanical properties through geometry rather than composition 1-4. Although lightweight, high-porosity microarchitectured materials can have high stiffness and strength, stress concentrations within the microstructure can cause flaw intolerance under cyclic loading 5,6, limiting fatigue life. However, it is not known how microarchitecture contributes to fatigue life. Naturally occurring materials can display exceptional mechanical performance and are useful models for the design of microarchitectured materials 7,8. Cancellous bone is a naturally occurring microarchitectured material that often survives decades of habitual cyclic loading without failure. Here we show that resistance to fatigue failure in cancellous bone is sensitive to the proportion of material oriented transverse to applied loads - a 30% increase in density caused by thickening transversely oriented struts increases fatigue life by 10-100 times. This finding is surprising in that transversely oriented struts have negligible effects on axial stiffness, strength and energy absorption. The effects of transversely oriented material on fatigue life are also present in synthetic lattice microstructures. In both cancellous bone and synthetic microarchitectures, the fatigue life can be predicted using the applied cyclic stress after adjustment for apparent stiffness and the proportion of the microstructure oriented transverse to applied loading. In the design of microarchitectured materials, stiffness, strength and energy absorption is often enhanced by aligning the microstructure in a preferred direction. Our findings show that introduction of such anisotropy, by reducing the amount of material oriented transverse to loading, comes at the cost of reduced fatigue life. Fatigue failure of durable devices and components generates substantial economic costs associated with repair and replacement. As advancements in additive manufacturing expand the use of microarchitectured materials to reusable devices including aerospace applications, it is increasingly necessary to balance the need for fatigue life with those of strength and density.

bioengineering↗