Two well-known pathways for the degradation of chloroplast proteins are via autophagy and senescence-associated vacuoles. Here, we describe a third pathway that was activated by senescence-and ...abiotic stress-induced expression of Arabidopsis thaliana CV (for chloroplast vesiculation). After targeting to the chloroplast, CV destabilized the chloroplast, inducing the formation of vesicles. CV-containing vesicles carrying stronfiai proteins, envelope membrane proteins, and thylakoid membrane proteins were released from the chloroplasts and mobilized to the vacuole for proteolysis. Overexpression of CV caused chloroplast degradation and premature leaf senescence, whereas silencing CV delayed chloroplast turnover and senescence induced by abiotic stress. Transgenic CIA-silenced plants displayed enhanced tolerance to drought, salinity, and oxidative stress. Immunoprecipitation and bimolecular fluorescence complementation assays demonstrated that CV interacted with photosystem II subunit PsbO1 in vivo through a C-terminal domain that is highly conserved in the plant kingdom. Collectively, our work indicated that CV plays a crucial role in stress-induced chloroplast disruption and mediates a third pathway for chloroplast degradation. From a biotechnological perspective, silencing of CV offers a suitable strategy for the generation of transgenic crops with increased tolerance to abiotic stress.
Abstract
The first discovered extrasolar worlds—giant, “hot Jupiter” planets on short-period orbits—came as a surprise to solar system–centric models of planet formation, prompting the development of ...new theories for planetary system evolution. The near absence of observed nearby planetary companions to hot Jupiters has been widely quoted as evidence in support of high-eccentricity tidal migration, a framework in which hot Jupiters form further out in their natal protoplanetary disks before being thrown inward with extremely high eccentricities, stripping systems of any close-in planetary companions. In this work, we present new results from a search for transit timing variations across the full 4 yr Kepler data set, demonstrating that at least 12% ± 6% of hot Jupiters have a nearby planetary companion. This subset of hot Jupiters is expected to have a quiescent dynamical history such that the systems could retain their nearby companions. We also demonstrate a ubiquity of nearby planetary companions to warm Jupiters (≥70% ± 16%), indicating that warm Jupiters typically form quiescently. We conclude by combining our results with existing observational constraints to propose an “eccentric migration” framework for the formation of short-period giant planets through postdisk dynamical sculpting in compact multiplanet systems. Our framework suggests that hot Jupiters constitute the natural end stage for giant planets spanning a wide range of eccentricities, with orbits that reach small enough periapses—either from their final orbital configurations in the disk phase or from eccentricity excitation in the postdisk phase—to trigger efficient tidal circularization.
Abstract
We present an estimate of the occurrence rate of hot Jupiters (7
R
⊕
≤
R
p
≤ 2
R
J
, 0.8 ≤
P
b
≤ 10 days) around early-type M dwarfs based on stars observed by the Transiting Exoplanet ...Survey Satellite (TESS) during its primary mission. We adopt stellar parameters from the TESS Input Catalog and construct a sample of 60,819 M dwarfs with 10.5 ≤
T
mag
≤ 13.5, effective temperatures 2900 ≤
T
eff
≤ 4000 K, and stellar masses 0.45 ≤
M
*
≤ 0.65
M
⊙
. We conduct a uninformed transit search using a detection pipeline based on the box least square search and characterize the searching completeness through an injection and recovery experiment. We combine a series of vetting steps including light centroid measurement, odd/even and secondary eclipse analysis, rotation and transit period synchronization tests as well as inspecting the ground-based photometric, spectroscopic, and imaging observations. Finally, we find a total of nine planet candidates, all of which are known TESS objects of interest. We obtain an occurrence rate of 0.27% ± 0.09% for hot Jupiters around early-type M dwarfs that satisfy our selection criteria. Compared with previous studies, the occurrence rate of hot Jupiters around early-type M dwarfs is smaller than all measurements for FGK stars, although they are consistent within 1
σ
–2
σ
. There is a trend that the occurrence rate of hot Jupiters has a peak at G dwarfs and falls toward both hotter and cooler stars. Combining results from transit, radial velocity, and microlensing surveys, we find that hot Jupiters around early-type M dwarfs possibly show a steeper decrease in the occurrence rate per logarithmic semimajor axis bin (
dN
/
d
log
10
a
) when compared with FGK stars.
Abstract The ubiquity of “peas-in-a-pod” architectural patterns and the existence of the radius valley each presents a striking population-level trend for planets with R p ≤ 4 R ⊕ that serves to ...place powerful constraints on the formation and evolution of these subgiant worlds. As it has yet to be determined whether the strength of this peas-in-a-pod uniformity differs on either side of the radius valley, we separately assess the architectures of systems containing only small ( R p ≤ 1.6 R ⊕ ), rocky planets from those harboring only intermediate-sized (1.6 R ⊕ < R p ≤ 4 R ⊕ ), volatile-rich worlds to perform a novel statistical comparison of intra-system planetary uniformity across compositionally distinct regimes. We find that, compared to their volatile-rich counterparts, rocky systems are less uniform in mass (2.6 σ ) but more uniform in size (4.0 σ ) and spacing (3.0 σ ). We provide further statistical validation for these results, demonstrating that they are not substantially influenced by the presence of mean-motion resonances, low-mass host stars, alternative bulk compositional assumptions, sample size effects, or detection biases. We also obtain tentative evidence (>2 σ significance) that the enhanced size uniformity of rocky systems is dominated by the presence of super-Earths (1 R ⊕ ≤ R p ≤ 1.6 R ⊕ ), while their enhanced mass diversity is driven by the presence of sub-Earth ( R p < 1 R ⊕ ) worlds.
Abstract
In protoplanetary disks, sufficiently massive planets excite pressure bumps, which can then be preferred locations for forming new planet cores. We discuss how this loop may affect the ...architecture of multiplanet systems and compare our predictions with observations. Our main prediction is that low-mass planets and giant planets can each be divided into two subpopulations with different levels of mass uniformity. Low-mass planets that can and cannot reach the pebble isolation mass (the minimum mass required to produce a pressure bump) develop into intra-system similarity “super-Earths” and more diverse “Earths,” respectively. Gas giants that do and do not accrete envelopes quickly develop into similar “Jupiters” and more diverse “Saturns,” respectively. Super-Earths prefer to form long chains via repeated pressure-bump planet formation, while Jupiter formation is usually terminated at pairs or triplets due to dynamical instability. These predictions are broadly consistent with observations. In particular, we discover a previously overlooked mass uniformity dichotomy among the observed populations of both low-mass planets (Earths versus super-Earths) and gas giants (Saturns versus Jupiters). For low-mass planets, planets well below the pebble isolation mass (≲3
M
⊕
or ≲1.5
R
⊕
for Sun-like stars) show significantly higher intra-system pairwise mass differences than planets around the pebble isolation mass. For gas giants, the period ratios of intra-system pairs show a bimodal distribution, which can be interpreted as two subpopulations with different levels of mass uniformity. These findings suggest that pressure-bump planet formation could be an important ingredient in shaping planetary architectures.
Abstract
Super-Earths within the same close-in, compact planetary system tend to exhibit a striking degree of uniformity in their radius, mass, and orbital spacing, and this “peas-in-a-pod” ...phenomenon itself serves to provide one of the strongest constrains on planet formation at large. While it has been recently demonstrated from independent samples that such planetary uniformity occurs for both configurations near and distant from mean motion resonance, the question thus remains if the strength of this uniformity itself differs between near-resonant and nonresonant configurations such that the two modes may be astrophysically distinct in their evolution. We thus provide in this work a novel comparative size uniformity analysis for 48 near-resonant and 251 nonresonant multiplanet systems from the California Kepler Survey catalog, evaluating uniformity both across systems and between planetary pairs within the same system. We find that while multiplanet configurations exhibit strong peas-in-a-pod size uniformity regardless of their proximity to resonance, near-resonant configurations display enhanced intra-system size uniformity as compared to their analogous nonresonant counterparts at the level of both entire systems and subsystem planetary pairs and chains. These results are broadly consistent with a variety of formation paradigms for multiple-planet systems, such as convergent migration within a turbulent protoplanetary disk or planet–planet interactions incited by postnebular dynamical instabilities. Nevertheless, further investigation is necessary to ascertain whether the nonresonant and near-resonant planetary configurations respectively evolve via a singular process or mechanisms that are dynamically distinct.
Abstract
Although close-orbiting, massive exoplanets—known as hot and warm Jupiters—are among the most observationally accessible known planets, their formation pathways are still not universally ...agreed upon. One method to constrain the possible dynamical histories of such planets is to measure the systems’ sky-projected spin–orbit angles using the Rossiter–McLaughlin effect. By demonstrating whether planets orbit around the stellar equator or on offset orbits, Rossiter–McLaughlin observations offer clues as to whether the planet had a quiescent or violent formation history. Such measurements are, however, only a reliable window into the history of the system if the planet in question orbits sufficiently far from its host star; otherwise, tidal interactions with the host star can erase evidence of past dynamical upheavals. We present a WIYN/NEID Rossiter–McLaughlin measurement of the tidally detached (
a
/
R
*
=
13.18
−
0.37
+
0.35
) warm Jupiter WASP-106 b, which orbits a star along the Kraft break (
T
eff
= 6002 ± 164 K). We find that WASP-106 b is consistent with a low spin–orbit angle (
λ
=
6
−
16
+
17
°
and
ψ
=
26
−
17
+
12
°
), suggesting a relatively quiescent formation history for the system. We conclude by comparing the stellar obliquities of hot and warm Jupiter systems, with the WASP-106 system included, to gain insight into the possible formation routes of these populations of exoplanets.
Abstract
The mechanisms responsible for generating spin–orbit misalignments in exoplanetary systems are still not fully understood. It is unclear whether these misalignments are related to the ...migration of hot Jupiters or are a consequence of general star and planet formation processes. One promising method to address this question is to constrain the distribution of spin–orbit angle measurements for a broader range of planets beyond hot Jupiters. In this work, we present the sky-projected obliquity (
λ
=
−
68
.°
1
−
14.7
+
21.2
) for the warm sub-Saturn TOI-1842b, obtained through a measurement of the Rossiter–McLaughlin effect using WIYN/NEID. From this, we determine the resulting 3D obliquity (
ψ
) to be
ψ
=
73
.°
3
−
12.9
+
16.3
. As the first spin–orbit angle determination made for a sub-Saturn-mass planet around a massive (
M
*
= 1.45
M
☉
) star, our result presents an opportunity to examine the orbital geometries for new regimes of planetary systems. When combined with archival measurements, our observations of TOI-1842b support the hypothesis that the previously established prevalence of misaligned systems around hot, massive stars may be driven by planet–planet dynamical interactions. In massive stellar systems, multiple gas giants are more likely to form and can then dynamically interact with each other to excite spin–orbit misalignments.
Abstract
The evolutionary history of an extrasolar system is, in part, fossilized through its planets’ orbital orientations relative to the host star’s spin axis. However, spin–orbit constraints for ...warm Jupiters—particularly in binary star systems, which are amenable to a wide range of dynamical processes—are relatively scarce. We report a measurement of the Rossiter–McLaughlin effect, observed with the Keck/HIRES spectrograph, across the transit of Qatar-6 A b—a warm Jupiter orbiting one star within a binary system. From this measurement, we obtain a sky-projected spin–orbit angle
λ
= 0.°1 ± 2.°6. Combining this new constraint with the stellar rotational velocity of Qatar-6 A that we measure from TESS photometry, we derive a true obliquity
ψ
=
21.82
−
18.36
+
8.86
°
—consistent with near-exact alignment. We also leverage astrometric data from Gaia DR3 to show that the Qatar-6 binary star system is edge-on (
i
B
=
90.17
−
1.06
+
1.07
°
), such that the stellar binary and the transiting exoplanet orbit exhibit line-of-sight orbit–orbit alignment. Ultimately, we demonstrate that all current constraints for the three-body Qatar-6 system are consistent with both spin–orbit and orbit–orbit alignment. High-precision measurements of the projected stellar spin rate of the host star and the sky-plane geometry of the transit relative to the binary plane are required to conclusively verify the full 3D configuration of the system.
Heat shock transcription factors (HSFs) play a crucial role in regulating plant growth and response to various abiotic stresses. In this study, we conducted a comprehensive analysis of the AeHSF gene ...family at genome-wide level in kiwifruit (Actinidia eriantha), focusing on their functions in the response to abiotic stresses. A total of 41 AeHSF genes were identified and categorized into three primary groups, namely, HSFA, HSFB, and HSFC. Further transcriptome analysis revealed that the expression of AeHSFA2b/2c and AeHSFB1c/1d/2c/3b was strongly induced by salt, which was confirmed by qRT-PCR assays. The overexpression of AeHSFA2b in Arabidopsis significantly improved the tolerance to salt stress by increasing AtRS5, AtGolS1 and AtGolS2 expression. Furthermore, yeast one-hybrid, dual-luciferase, and electrophoretic mobility shift assays demonstrated that AeHSFA2b could bind to the AeRFS4 promoter directly. Therefore, we speculated that AeHSFA2b may activate AeRFS4 expression by directly binding its promoter to enhance the kiwifruit’s tolerance to salt stress. These results will provide a new insight into the evolutionary and functional mechanisms of AeHSF genes in kiwifruit.
PDF
