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Turnover of dysfunctional organelles is vital to maintain homeostasis in eukaryotic cells. As photosynthetic organelles, plant chloroplasts can suffer sunlight-induced damage. However, the process for turnover of entire damaged chloroplasts remains unclear. Here, we demonstrate that autophagy is responsible for the elimination of sunlight-damaged, collapsed chloroplasts in Arabidopsis thaliana. We found that vacuolar transport of entire chloroplasts, termed chlorophagy, was induced by UV-B damage to the chloroplast apparatus. This transport did not occur in autophagy-defective atg mutants, which exhibited UV-B-sensitive phenotypes and accumulated collapsed chloroplasts. Use of a fluorescent protein marker of the autophagosomal membrane allowed us to image autophagosome-mediated transport of entire chloroplasts to the central vacuole. In contrast to sugar starvation, which preferentially induced distinct type of chloroplast-targeted autophagy that transports a part of stroma via the Rubisco-containing body (RCB) pathway, photooxidative damage induced chlorophagy without prior activation of RCB production. We further showed that chlorophagy is induced by chloroplast damage caused by either artificial visible light or natural sunlight. Thus, this report establishes that an autophagic process eliminates entire chloroplasts in response to light-induced damage.

A bstract We show a new mechanism for baryogenesis where the reheating temperature can be smaller than the electroweak scale. The baryon number symmetry is violated by a dimension nine operator which conserves a baryon parity. A high energy quark from the decay of a heavy particle, e.g. inflaton, modulus or gravitino, undergoes flavor oscillation, and is thermalized due to the scatterings with the ambient thermal plasma. We point out that the baryon asymmetry of our universe can be generated due to the scatterings via the baryon number violating operator. Our scenario can be tested in neutron-antineutron oscillation experiments as well as other terrestrial experiments.

Plant chloroplasts constantly accumulate damage caused by visible wavelengths of light during photosynthesis. Our previous study revealed that entire photodamaged chloroplasts are subjected to vacuolar digestion through an autophagy process termed chlorophagy; however, how this process is induced and executed remained poorly understood. In this study, we monitored intracellular induction of chlorophagy in Arabidopsis (Arabidopsis thaliana) leaves and found that mesophyll cells damaged by high visible light displayed abnormal chloroplasts with a swollen shape and 2.5 times the volume of normal chloroplasts. In wild-type plants, the activation of chlorophagy decreased the number of swollen chloroplasts. In the autophagy-deficient autophagy mutants, the swollen chloroplasts persisted, and dysfunctional chloroplasts that had lost chlorophyll fluorescence accumulated in the cytoplasm. Chloroplast swelling and subsequent induction of chlorophagy were suppressed by the application of exogenous mannitol to increase the osmotic pressure outside chloroplasts or by overexpression of VESICLE INDUCING PROTEIN IN PLASTID1, which maintains chloroplast envelope integrity. Microscopic observations of autophagy-related membranes showed that swollen chloroplasts were partly surrounded by autophagosomal structures and were engulfed directly by the tonoplast, as in microautophagy. Our results indicate that an elevation in osmotic potential inside the chloroplast due to high visible light-derived envelope damage results in chloroplast swelling and serves as an induction factor for chlorophagy, and this process mobilizes entire chloroplasts via tonoplast-mediated sequestering to avoid the cytosolic accumulation of dysfunctional chloroplasts.

A bstract We discuss a QCD-scale composite axion model arising from dark QCD coupled to QCD. The presently proposed scenario not only solves the strong CP problem, but also is compatible with the preheating setup for the QCD baryogenesis. The composite axion is phenomenologically required to mimic the QCD pion, but can generically be flavorful, which could be testable via the induced flavor changing processes at experiments. Another axionlike particle (ALP) is predicted to achieve the axion relaxation mechanism, which can phenomenologically act as the conventional QCD axion. This ALP can be ultralight, having the mass less than 1 eV, to be a dark matter candidate. The QCD × dark QCD symmetry structure constrains dark QCD meson spectra, so that the dark η ′-like meson would only be accessible at the collider experiments. Still, the Belle II and Electron ion collider experiments can have a high enough sensitivity to probe the dark η ′-like meson in the diphoton channel, which dominantly arises from the mixing with the QCD η ′ and the pionic composite axion. We also briefly address nontrivial cosmological aspects, such as those related to the dark-chiral phase transition, the dark matter production, and an ultraviolet completion related to the ultralight ALP.

Autophagy is an intracellular process leading to the vacuolar degradation of cytoplasmic components. Autophagic degradation of chloroplasts is particularly activated in leaves under conditions of low sugar availability. Here, we investigated the importance of autophagy in the energy availability and growth of Arabidopsis (Arabidopsis thaliana). autophagy-deficient (atg) mutants showed reduced growth under short-day conditions. This growth inhibition was largely relieved under continuous light or under short-day conditions combined with feeding of exogenous sucrose, suggesting that autophagy is involved in energy production at night for growth. Arabidopsis accumulates starch during the day and degrades it for respiration at night. Nighttime energy availability is perturbed in starchless mutants, in which a lack of starch accumulation causes a transient sugar deficit at night. We generated starchless and atg double mutants and grew them under different photoperiods. The double mutants showed more severe phenotypes than did atg or starchless single mutants: reduced growth and early cell death in leaves were observed when plants were grown under 10-h photoperiods. Transcript analysis of dark-inducible genes revealed that the sugar starvation symptoms observed in starchless mutants became more severe in starchless atg double mutants. The contents of free amino acids (AAs) increased, and transcript levels of several genes involved in AA catabolism were elevated in starchless mutant leaves. The increases in branched-chain AA and aromatic AA contents were partially compromised in starchless atg double mutants. We conclude that autophagy can contribute to energy availability at night by providing a supply of alternative energy sources such as AAs.

Breaking the Pecci–Quinn (PQ) symmetry by the perturbative dynamics would suffer from a hierarchy problem, just like the electroweak symmetry breaking in the standard model. The dynamics of the axion, associated with the PQ symmetry breaking, would also involve a triviality problem. We provide a paradigm to resolve those two problems potentially existing in the PQ symmetry breaking scenario, with keeping the successful axion relaxation for the QCD strong CP phase. The proposed theory includes an axicolor dynamics with the axicolored fermions partially gauged by the QCD color, and is shown to be governed by an asymptotically safe (AS) fixed point: quantum scale invariance is built. The AS axicolor is actually a “walking” dynamics, which dynamically breaks a PQ symmetry, a part of the chiral symmetry carried by the axicolored fermions. The PQ scale generation is then triggered by the nonperturbative dimensional transmutation in the “walking” dynamics. A composite axion emerges as the associated Nambu-Goldstone boson. That is, no hierarchy or triviality problem is present there. The composite axion can potentially be light due to the characteristic feature of the AS axicolor (“walking” axicolor), becomes the QCD axion in the anti-Veneziano limit, and gets heavier by the subleading correction. The composite axion relaxes the QCD theta parameter, involving heavier relaxation partners such as axicolored pseudoscalar mesons, and the ultraviolet correction to the relaxation mechanism is protected by the established (near) scale invariance during the “walking” regime.

A bstract We consider the minimal seesaw model, the Standard Model extended by two right-handed neutrinos, for explaining the neutrino masses and mixing angles measured in oscillation experiments. When one of right-handed neutrinos is lighter than the electroweak scale, it can give a sizable contribution to neutrinoless double beta (0 νββ ) decay. We show that the detection of the 0 νββ decay by future experiments gives a significant implication to the search for such a light right-handed neutrino.

A bstract We propose a hybrid inflationary scenario based on eight-flavor hidden QCD with the hidden colored fermions being in part gauged under U(1) B−L . This hidden QCD is almost scale-invariant, so-called walking, and predicts the light scalar meson (the walking dilaton) associated with the spontaneous scale breaking, which develops the Coleman-Weinberg (CW) type potential as the consequence of the nonperturbative scale anomaly, hence plays the role of an inflaton of the small-field inflation. The U(1) B−L Higgs is coupled to the walking dilaton inflaton, which is dynamically induced from the so-called bosonic seesaw mechanism. We explore the hybrid inflation system involving the walking dilaton inflaton and the U(1) B−L Higgs as a waterfall field. We find that observed inflation parameters tightly constrain the U(1) B−L breaking scale as well as the walking dynamical scale to be ~ 10 9 GeV and ~ 10 14 GeV, respectively, so as to make the waterfall mechanism worked. The lightest walking pion mass is then predicted to be around 500 GeV. Phenomenological perspectives including embedding of the dynamical electroweak scalegenesis and possible impacts on the thermal leptogenesis are also addressed.

A bstract Ultra-supercooling phase transitions can generate large overdensities in the Universe, potentially leading to the formation of primordial black holes (PBHs), which can also be a dark matter candidate. In this work, we focus on the supercooling phase transition for the scale symmetry breaking based on the effective potential of the Coleman-Weinberg (CW) type. We investigate the effect on the PBH production in the presence of an additional mass term for the CW scalar field, what we call a soft-scale breaking term, which serves as the extra explicit-scale breaking term other than the quantum scale anomaly induced by the CW mechanism. We demonstrate that even a small size of the soft-scale breaking term can significantly affect the PBH production depending on its sign: a positive term slows down the phase transition, thereby enhancing the PBH abundance and improving the model’s ability to account for dark matter; in contrast, a negative term suppresses the PBH formation. The inclusion of such soft-scale breaking terms broadens the viable parameter space and increases the flexibility of the framework. We further illustrate our results through two ultraviolet-complete realizations: i) a many-flavor QCD-inspired model as a reference model which can dynamically induce a positive-soft scale breaking; ii) a Higgs portal model with a B – L scalar as the benchmark for the case where a negative-soft scale breaking is induced. Our study would provide a new testable link between PBH dark matter and gravitational wave signatures in the CW-type scenario.