Video1_The evolution of a spot–spot-type solar active region which produced a major solar eruption.MP4

Solar active regions are the main sources of large solar flares and coronal mass ejections. It is found that the active regions producing large eruptions usually show compact, highly sheared polarity inversion lines. A scenario named “collisional shearing” is proposed to explain the formation of this type of polarity inversion lines and the subsequent eruptions, which stresses the role of collision and shearing induced by relative motions of different bipoles in their emergence. However, in observations, if not considering the evolution stage of the active regions, about one-third of the active regions that produce large solar eruptions govern a spot–spot-type configuration. In this work, we studied the full evolution of an emerging AR, which showed a spot–spot-type configuration when producing a major eruption, to explore the possible evolution gap between the “collisional shearing” process in flux emergence and the formation of the spot–spot-type, eruption-producing AR. We tracked the AR from the very beginning of its emergence until it produced the first major eruption. It was found that the AR was formed through three bipoles emerging sequentially. The bipoles were arranged in parallel on the photosphere, shown as two clusters of sunspots with opposite-sign polarities, so that the AR exhibited an overall large bipole configuration. In the fast emergence phase of the AR, the shearing gradually occurred due to the proper motions of the polarities, but no significant collision occurred due to the parallel arrangement of the bipoles nor did the large eruption occur. After the fast emergence phase, one large positive polarity started to show signs of decay. Its dispersion led to the collision to a negative polarity which belonged to another bipole. A huge hot channel spanning the entire AR was formed through precursor flarings around the collision region. The hot channel erupted later, accompanied by an M7.3-class flare. The results suggest that in the spot–spot-type AR, along with the shearing induced by the proper motions of the polarities, a decay process may lead to the collision of the polarities, driving the subsequent eruptions.</p

Video2_The evolution of a spot–spot-type solar active region which produced a major solar eruption.MP4

Solar active regions are the main sources of large solar flares and coronal mass ejections. It is found that the active regions producing large eruptions usually show compact, highly sheared polarity inversion lines. A scenario named “collisional shearing” is proposed to explain the formation of this type of polarity inversion lines and the subsequent eruptions, which stresses the role of collision and shearing induced by relative motions of different bipoles in their emergence. However, in observations, if not considering the evolution stage of the active regions, about one-third of the active regions that produce large solar eruptions govern a spot–spot-type configuration. In this work, we studied the full evolution of an emerging AR, which showed a spot–spot-type configuration when producing a major eruption, to explore the possible evolution gap between the “collisional shearing” process in flux emergence and the formation of the spot–spot-type, eruption-producing AR. We tracked the AR from the very beginning of its emergence until it produced the first major eruption. It was found that the AR was formed through three bipoles emerging sequentially. The bipoles were arranged in parallel on the photosphere, shown as two clusters of sunspots with opposite-sign polarities, so that the AR exhibited an overall large bipole configuration. In the fast emergence phase of the AR, the shearing gradually occurred due to the proper motions of the polarities, but no significant collision occurred due to the parallel arrangement of the bipoles nor did the large eruption occur. After the fast emergence phase, one large positive polarity started to show signs of decay. Its dispersion led to the collision to a negative polarity which belonged to another bipole. A huge hot channel spanning the entire AR was formed through precursor flarings around the collision region. The hot channel erupted later, accompanied by an M7.3-class flare. The results suggest that in the spot–spot-type AR, along with the shearing induced by the proper motions of the polarities, a decay process may lead to the collision of the polarities, driving the subsequent eruptions.</p

Video3_The evolution of a spot–spot-type solar active region which produced a major solar eruption.MP4

Solar active regions are the main sources of large solar flares and coronal mass ejections. It is found that the active regions producing large eruptions usually show compact, highly sheared polarity inversion lines. A scenario named “collisional shearing” is proposed to explain the formation of this type of polarity inversion lines and the subsequent eruptions, which stresses the role of collision and shearing induced by relative motions of different bipoles in their emergence. However, in observations, if not considering the evolution stage of the active regions, about one-third of the active regions that produce large solar eruptions govern a spot–spot-type configuration. In this work, we studied the full evolution of an emerging AR, which showed a spot–spot-type configuration when producing a major eruption, to explore the possible evolution gap between the “collisional shearing” process in flux emergence and the formation of the spot–spot-type, eruption-producing AR. We tracked the AR from the very beginning of its emergence until it produced the first major eruption. It was found that the AR was formed through three bipoles emerging sequentially. The bipoles were arranged in parallel on the photosphere, shown as two clusters of sunspots with opposite-sign polarities, so that the AR exhibited an overall large bipole configuration. In the fast emergence phase of the AR, the shearing gradually occurred due to the proper motions of the polarities, but no significant collision occurred due to the parallel arrangement of the bipoles nor did the large eruption occur. After the fast emergence phase, one large positive polarity started to show signs of decay. Its dispersion led to the collision to a negative polarity which belonged to another bipole. A huge hot channel spanning the entire AR was formed through precursor flarings around the collision region. The hot channel erupted later, accompanied by an M7.3-class flare. The results suggest that in the spot–spot-type AR, along with the shearing induced by the proper motions of the polarities, a decay process may lead to the collision of the polarities, driving the subsequent eruptions.</p

Video4_The evolution of a spot–spot-type solar active region which produced a major solar eruption.MP4

Solar active regions are the main sources of large solar flares and coronal mass ejections. It is found that the active regions producing large eruptions usually show compact, highly sheared polarity inversion lines. A scenario named “collisional shearing” is proposed to explain the formation of this type of polarity inversion lines and the subsequent eruptions, which stresses the role of collision and shearing induced by relative motions of different bipoles in their emergence. However, in observations, if not considering the evolution stage of the active regions, about one-third of the active regions that produce large solar eruptions govern a spot–spot-type configuration. In this work, we studied the full evolution of an emerging AR, which showed a spot–spot-type configuration when producing a major eruption, to explore the possible evolution gap between the “collisional shearing” process in flux emergence and the formation of the spot–spot-type, eruption-producing AR. We tracked the AR from the very beginning of its emergence until it produced the first major eruption. It was found that the AR was formed through three bipoles emerging sequentially. The bipoles were arranged in parallel on the photosphere, shown as two clusters of sunspots with opposite-sign polarities, so that the AR exhibited an overall large bipole configuration. In the fast emergence phase of the AR, the shearing gradually occurred due to the proper motions of the polarities, but no significant collision occurred due to the parallel arrangement of the bipoles nor did the large eruption occur. After the fast emergence phase, one large positive polarity started to show signs of decay. Its dispersion led to the collision to a negative polarity which belonged to another bipole. A huge hot channel spanning the entire AR was formed through precursor flarings around the collision region. The hot channel erupted later, accompanied by an M7.3-class flare. The results suggest that in the spot–spot-type AR, along with the shearing induced by the proper motions of the polarities, a decay process may lead to the collision of the polarities, driving the subsequent eruptions.</p

Distinct Effects of Abelson Kinase Mutations on Myocytes and Neurons in Dissociated <i>Drosophila</i> Embryonic Cultures: Mimicking of High Temperature

<div><p>Abelson tyrosine kinase (Abl) is known to regulate axon guidance, muscle development, and cell-cell interaction <i>in vivo.</i> The <i>Drosophila</i> primary culture system offers advantages in exploring the cellular mechanisms mediated by Abl with utilizing various experimental manipulations. Here we demonstrate that single-embryo cultures exhibit stage-dependent characteristics of cellular differentiation and developmental progression in neurons and myocytes, as well as nerve-muscle contacts. In particular, muscle development critically depends on the stage of dissociated embryos. In wild-type (WT) cultures derived from embryos before stage 12, muscle cells remained within cell clusters and were rarely detected. Interestingly, abundant myocytes were spotted in <i>Abl</i> mutant cultures, exhibiting enhanced myocyte movement and fusion, as well as neuron-muscle contacts even in cultures dissociated from younger, stage 10 embryos. Notably, <i>Abl</i> myocytes frequently displayed well-expanded lamellipodia. Conversely, <i>Abl</i> neurons were characterized with fewer large veil-like lamellipodia, but instead had increased numbers of filopodia and darker nodes along neurites. These distinct phenotypes were equally evident in both homo- and hetero-zygous cultures (<i>Abl/Abl</i> vs. <i>Abl</i>/+) of different alleles (<i>Abl¹ and Abl⁴</i>) indicating dominant mutational effects. Strikingly, in WT cultures derived from stage 10 embryos, high temperature (HT) incubation promoted muscle migration and fusion, partially mimicking the advanced muscle development typical of <i>Abl</i> cultures. However, HT enhanced neuronal growth with increased numbers of enlarged lamellipodia, distinct from the characteristic <i>Abl</i> neuronal morphology. Intriguingly, HT incubation also promoted <i>Abl</i> lamellipodia expansion, with a much greater effect on nerve cells than muscle. Our results suggest that Abl is an essential regulator for myocyte and neuron development and that high-temperature incubation partially mimics the faster muscle development typical of <i>Abl</i> cultures. Despite the extensive alterations by <i>Abl</i> mutations, we observed myocyte fusion events and nerve-muscle contact formation between WT and <i>Abl</i> cells in mixed WT and <i>Abl</i> cultures derived from labeled embryos.</p></div

Promotion of muscle lamellipodia development and interaction with neurons in <i>Abl</i> cultures.

<p>A–D) Samples of phase contrast images (100X) displaying lamellipodia from WT and <i>Abl</i> muscle cells in culture. (A) is from cultures incubated 7D, (B–D) are from cultures incubated 24 h–48 h. WT cultures from advanced embryos (stage 12) produce expanded lamellipodia when incubated at RT (A), whereas cultures derived from earlier embryos (stage 10) show muscle cells only after HT incubation, which display microspikes but rarely well extended lamellipodia (B). <i>Abl</i> cultures exhibit more abundant lamellipodia at stage 10 following incubation at RT (C) or HT (D). E) Example of neuron-muscle interactions in HT-incubated <i>Abl</i> cultures. Time lapse images (phase contrast, 40X) taken 24 hours (E1) and 39 hours (E2) after plating. Neuronal filopodia and muscle lamellipodia first approached each other (E1) and subsequently formed morphological connection (E2). Arrows indicate the interaction site. Scale bars, 10 µm.</p

Mitochondria are highly enriched in the dark nodules along neurites of <i>Abl</i> neurons.

<p>A1–B1) Phase contrast images of phase dark nodules and phase light lamellipodia from WT (RT) and <i>Abl</i> (HT) neutires (100X). A2–B2) Merged fluorescent and phase contrast images showing locations of Rh123 staining. Arrowheads, phase light growth cones. Arrows, phase dark structures along the neurite that accumulate Rh123 staining. The staining indicates that dark nodules in <i>Abl</i> are enriched with mitochondria and possibly other organelles. Age of cultures, 2–4 days. All cultures were derived from stage 10 embryos. Scale bar, 10 µm.</p

Sample of muscle cell elongation and fusion in HT-incubated WT culture.

<p>Time lapse phase contrast images (100X) taken 39 hours (A) and 46 hours (B1) after plating. Arrows denote an example of muscle elongation. B2) Enlarged DIC image of the boxed area in B1. Arrowhead indicates a potential fusion site. All cultures were derived from stage 10 embryos. Scale bars, 10 µm.</p

Comparison of the Abelson Kinase mutation and high-temperature effects on neuronal growth.

<p>Phase contrast images (100X) of stage 10 WT and <i>Abl</i> cultures grown at room temperature (RT) or high temperature (HT, 30°C). A1 vs. B1) In RT cultures, <i>Abl</i> neurons show enhanced growth of filopodia compare to WT. There is also an increase in dark nodules along the neurite and at the terminal (B1, arrowheads). However, while phase-light growth cones with expanded lamellipodia are rare in <i>Abl</i>, they can readily be seen in WT (A1, arrow). A1 vs. A2) HT incubation of WT neurons produces extremely large growth cones (A2, arrows). B1 vs. B2) HT incubation of <i>Abl</i> neurons enhances development of phase-light lamellipodia at growth cones and along neurites (B2, arrows). All cultures were incubated 3–6 days. Scale bars, 10 µm.</p

High-temperature incubation promotes muscle development in cultures from stage 10 WT embryos.

<p>A) WT cultures from stage 10 embryos rarely presented any muscle cells when incubated at RT (40X). B1) HT incubation of stage 10 WT cultures produced abundant muscle cells both in isolation and in association with cell clusters. Sample from culture after 39 h incubation at HT (40X), showing a muscle cell isolated from cell aggregations (arrow) and still others associated with cell clusters (arrowheads). B2–B3) WT cultures after 9 days incubation at HT (100X). B2) An unusually large WT multinucleated muscle cell (arrows pointing to nuclei) interacting with neurites from a neuron (soma not shown). B3) Enlarged image of boxed area in B2 displaying a neuromuscular contact. B2, phase contrast; A, B1, and B3, DIC images. Scale bars, 20 µm.</p