Current Biology最新文献

Red flowers are typically pollinated by birds. A new study demonstrates that UV-absorbing phenylpropanoid pigments represent a potential 'magic trait' in the evolution of red flowers in bird-pollinated species, conferring a threefold advantage by enhancing bird attraction, deterring bees, and protecting pollen from ultraviolet radiation.

How do organisms partition a multinucleated compartment into individual cells, each enclosing a single nucleus? While the best-studied organisms form orderly surface monolayers, a new report now describes the process of cellularization deep into the chytrid sporangium.

Color provides an important visual dimension for object detection and classification. In most animals, color and motion vision are largely separated throughout early stages of visual processing. However, accumulating evidence indicates crosstalk between chromatic and achromatic pathways. Here, we investigate the spectral sensitivity of the motion-vision pathway at the level of pre-motor descending neurons (DNs) in two butterfly species with different retinal compositions and wing coloration. Butterflies engage in fast, agile flight within often colorful visual ecologies, which may heighten evolutionary pressure to integrate color and motion vision. Indeed, we observed a separation of spectral sensitivities that matches the functional properties of butterfly DNs, such that wide-field, optic flow-sensitive DNs involved in stabilization reflexes have effective broadband spectral responses, while target-selective DNs involved in target tracking are comparatively narrowband and match conspecific wing coloration. Our findings demonstrate the spectral tuning of motion vision within a pre-motor neuronal bottleneck that controls behavior. VIDEO ABSTRACT.

In angiosperms, dioecy has evolved thousands of times, and the pathways underlying the required floral changes are therefore expected to exhibit diversity as well as parallelism. Here we investigate Itoa orientalis, a dioecious Salicaceae in which immature flowers are bisexual, but the stamens or pistils then abort. This contrasts with the floral development in dioecious species of Populus and Salix, which lack any morphologically bisexual stage. A haplotype-resolved Itoa genome assembly revealed an XY system of sex determination with a sex-determining region (SDR) spanning ∼6 Mb and encompassing the centromere. In females, the SDR contains an 11-bp deletion in the TAPETAL DEVELOPMENT and FUNCTION 1 (TDF1) gene that results in multiple premature stop codons. Experimental silencing of TDF1 in males led to defective stamens, providing direct evidence that TDF1 is a regulator of male function as it is in the phylogenetically distant dioecious Asparagus officinalis. A candidate gene for suppression of female function is the MINI ZINC FINGER 2 (MIF2) gene. These findings reveal that the Salicaceae family has both an ARR17-based one-gene sex-determining system in Populus and Salix, and a two-gene system in Itoa.

Adaptive behavior enables individuals to respond flexibly to environmental changes by forming expectations based on experience within the new environment. Beta oscillations (13-30 Hz), with their widespread distribution,^{1,2,3,4,5,6,7,8,9,10,11,12} play a central role in this process.^{13,14,15,16,17,18,19,20} Specifically, beta synchronization occurring 2 s before movement initiation is modulated by prior errors^21,22,23 and may reflect predictions based on past outcomes.^24,25,26,27 Yet, the spatiotemporal dynamics of pre-movement beta oscillations, as well as their roles in detecting environmental changes and in iteratively updating motor plans to optimize and stabilize performance, remain elusive. Here, we reveal that beta oscillations emerge in a cerebello-cortical network 2 s before action initiation and progressively build up across trials as environmental features are learned and behavioral outcomes become more stable. Within this network, directional connectivity analyses reveal that the cerebellum initially drives prefrontal activity during the pre-movement period, with this influence reversing near movement onset. Finally, using a single-trial approach, we establish that, before action initiation, beta bursts in this network predict performance in the upcoming trial based on previous outcomes. These findings identify pre-movement beta oscillations within a cerebello-cortical network as a neural substrate supporting predictive processes that stabilize motor performance across changing environments. They emphasize the contribution of cerebellar networks to cognitive aspects of motor control up to 2 s before movement onset.

The diversity of life we observe today is the product of deep-time diversification and extinction dynamics unfolding over hundreds of millions of years. Modeling these dynamics requires both phylogenies and fossil data, yet fossils are notoriously uneven in their temporal and taxonomic distribution. In their recent analysis of Hymenoptera, one of the great insect radiations, Jouault et al.¹ employed Bayesian Brownian Bridge (BBB) and PyRate² to estimate origination and extinction patterns. PyRate models diversification rates directly from fossil occurrence data, and the PyRate results appear to be dominated by gaps in the fossil record (Figure 1), suggesting that the inferred extinction events likely reflect overfitting to a sparse fossil record rather than robust signal of extinction.

Contractile tubes must establish organized actomyosin networks. A new study in Caenorhabditis elegans reports that a transient cell polarizes and shapes a valve cell, by both connecting at a junction that slides to expand the apical region of the valve cell as well as providing resistance to organize myosin recruitment to the valve.

Sleep is a universal and tightly regulated process that is controlled by both circadian and homeostatic mechanisms¹. Work in Drosophila melanogaster has shown that sleep homeostasis is largely governed by the dorsal fan-shaped body (dFB). Within this region, some dFB neurons monitor the need to sleep through changes in intrinsic excitability. As sleep pressure builds, their input-output function becomes biased toward spike generation, whereas excitability returns toward baseline after rebound sleep² in a process linked to mitochondrial reactive oxygen species (ROS)³. Prolonged periods of wakefulness elevate ROS-derived carbonyls, which are reduced by Hyperkinetic, an aldoketoreductase enzyme binding the cofactor NADP(H)^3,4. The resulting change in cofactor redox state decelerates potassium channel inactivation, increases excitability and promotes sleep^3,4. In line with this mechanism, dampening ROS levels and disrupting the excitability shift, or the Hyperkinetic-dependent redox-sensing mechanism, results in insomnia^2,3. Conversely, production of non-radical ROS at the plasma membrane, i.e., where the functional Shaker-Hyperkinetic ion channel complex is localized, increases the excitability of dFB neurons and promotes sleep^3,4. Together, these observations suggest that changes in mitochondrial oxidation in dFB neurons convey sleep need by coupling metabolic state to neuronal excitability^3,4,5. However, the original R23E10-GAL4 driver line used to identify this mechanism has been recently shown to also label sleep-promoting ventral nerve cord (VNC-SP) cells in addition to dFB neurons⁶. Although prior electrophysiological and imaging experiments only targeted dFB neurons^3,4,5, the interpretation of the sleep phenotypes may be confounded by contributions from both dFB and VNC-SP neurons. Indeed, a recent study suggested that dFB neurons may in fact not have a sleep-promoting role and that the redox-dependent mechanism may act in the ventral nerve cord instead⁷. To resolve this uncertainty, we directly compared the functional roles of dFB and VNC-SP neurons in redox-dependent sleep control using behavioral sleep assays, redox-state manipulations, and split-GAL4 (Sp-GAL4) lines that segregate these neuronal populations. As a result, we demonstrate that the redox-sensing mechanism operates specifically in dFB neurons to promote sleep.

Tissue growth is a result of cell proliferation and cell growth. Two new studies unravel a switch in the use of these two cellular behaviors to promote organ growth and a role for the basement membrane and the transcriptional coactivator Yorkie in regulating this switch.

Kinesin motors play diverse roles in cells, including spindle assembly and chromosome segregation. Each kinesin has three general domains-the motor head, neck, and tail. As microtubule (MT) motors, kinesins have directionality, walking toward the plus or minus end of an MT. Plus-end kinesins have their motor head at the N terminus, while minus-end kinesins have their motor head at the C terminus. Interestingly, in vitro data indicate that the motor head does not dictate directionality; instead, it is the neck. Here, we seek to understand the cellular function of each kinesin domain. We systematically created chimeras of fission yeast kinesin-6 Klp9 (a plus-end kinesin localized at the spindle midzone to slide the MTs and elongate the spindle) and kinesin-14 Pkl1 (a minus-end kinesin localized at the spindle poles to focus MTs). Our in vivo data reveal that the tail dictates cellular localization, and in some cases directionality of the motor head; the motor head produces binding and sliding forces affecting spindle function; and the neck modulates the forces of the motor head. Specifically, Pkl1-head, when put on Klp9-neck-tail, walks toward the spindle midzone and slides MTs faster than the wild-type Klp9. This results in spindle breakage and aneuploidy. In contrast, Klp9-head, when put on Pkl1-neck-tail, localizes to the spindle poles but fails to properly focus MTs, leading to abnormal MT protrusions. This results in asymmetric displacement of the chromosomes and aneuploidy. Our studies reveal domain-dependent control of motor localization, direction, and force production, whose dysfunctions lead to different modes of aneuploidy.