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1. The Arabidopsis heterotrimeric G‐protein β subunit, AGB 1, is required for guard cell calcium sensing and calcium‐induced calcium release

   https://doi.org/10.1111/tpj.14318  

   Jeon, Byeong Wook; Acharya, Biswa R.; Assmann, Sarah M. (April 2019, The Plant Journal)

   <bold>Summary</bold> Cytosolic calcium concentration ([Ca²⁺]_cyt) and heterotrimeric G‐proteins are universal eukaryotic signaling elements. In plant guard cells, extracellular calcium (Ca_o) is as strong a stimulus for stomatal closure as the phytohormone abscisic acid (ABA), but underlying mechanisms remain elusive. Here, we report that the sole Arabidopsis heterotrimeric Gβ subunit,AGB1, is required for four guard cell Ca_oresponses: induction of stomatal closure; inhibition of stomatal opening; [Ca²⁺]_cytoscillation; and inositol 1,4,5‐trisphosphate (InsP3) production. Stomata in wild‐type Arabidopsis (Col) and in mutants of the canonical Gα subunit,GPA1, showed inhibition of stomatal opening and promotion of stomatal closure by Ca_o. By contrast, stomatal movements ofagb1mutants andagb1/gpa1double‐mutants, as well as those of theagg1agg2 Gγ double‐mutant, were insensitive to Ca_o. These behaviors contrast withABA‐regulated stomatal movements, which involveGPA1 andAGB1/AGG3 dimers, illustrating differential partitioning of G‐protein subunits among stimuli with similar ultimate impacts, which may facilitate stimulus‐specific encoding.AGB1knockouts retained reactive oxygen species andNOproduction, but lostYC3.6‐detected [Ca²⁺]_cytoscillations in response to Ca_o, initiating only a single [Ca²⁺]_cytspike. Experimentally imposed [Ca²⁺]_cytoscillations restored stomatal closure inagb1. Yeast two‐hybrid and bimolecular complementation fluorescence experiments revealed thatAGB1 interacts with phospholipase Cs (PLCs), and Ca_oinduced InsP3 production in Col but not inagb1. In sum, G‐protein signaling viaAGB1/AGG1/AGG2 is essential for Ca_o‐regulation of stomatal apertures, and stomatal movements in response to Ca_oapparently require Ca²⁺‐induced Ca²⁺release that is likely dependent on Gβγ interaction withPLCs leading to InsP3 production. 

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2. On the Kinematics of Cold, Metal-enriched Galactic Fountain Flows in Nearby Star-forming Galaxies

   https://doi.org/10.3847/1538-4357/ac7b88  

   Rubin, Kate H. R.; Juarez, Christian; Cooksey, Kathy L.; Werk, Jessica K.; Prochaska, J. Xavier; O’Meara, John M.; Burchett, Joseph N.; Rickards Vaught, Ryan J.; Kulkarni, Varsha P.; Straka, Lorrie A. (September 2022, The Astrophysical Journal)

   Abstract We use medium-resolution Keck/Echellette Spectrograph and Imager spectroscopy of bright quasars to study cool gas traced by Caiiλλ3934, 3969 and Naiλλ5891, 5897 absorption in the interstellar/circumgalactic media of 21 foreground star-forming galaxies at redshifts 0.03 <z< 0.20 with stellar masses 7.4 ≤ logM_*/M_⊙≤ 10.6. The quasar–galaxy pairs were drawn from a unique sample of Sloan Digital Sky Survey quasar spectra with intervening nebular emission, and thus have exceptionally close impact parameters (R_⊥< 13 kpc). The strength of this line emission implies that the galaxies’ star formation rates (SFRs) span a broad range, with several lying well above the star-forming sequence. We use Voigt profile modeling to derive column densities and component velocities for each absorber, finding that column densitiesN(Caii) > 10^12.5cm⁻²(N(Nai) > 10^12.0cm⁻²) occur with an incidencef_C(Caii) = 0.63^+0.10_−0.11(f_C(Nai) = 0.57^+0.10_−0.11). We find no evidence for a dependence off_Cor the rest-frame equivalent widthsW_r(CaiiK) orW_r(Nai5891) onR_⊥orM_*. Instead,W_r(CaiiK) is correlated with local SFR at >3σsignificance, suggesting that Caiitraces star formation-driven outflows. While most of the absorbers have velocities within ±50 km s⁻¹of the host redshift, their velocity widths (characterized by Δv₉₀) are universally 30–177 km s⁻¹larger than that implied by tilted-ring modeling of the velocities of interstellar material. These kinematics must trace galactic fountain flows and demonstrate that they persist atR_⊥> 5 kpc. Finally, we assess the relationship between dust reddening andW_r(CaiiK) (W_r(Nai5891)), finding that 33% (24%) of the absorbers are inconsistent with the best-fit Milky WayE(B−V)-W_rrelations at >3σsignificance. 

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3. Photophysical Insights of Halogenated Dipyrrolonaphthyridine‐Diones as Potential Photodynamic Therapy Agents ^†

   https://doi.org/10.1111/php.13757  

   Morgan, Jayla; Yun, Young Ju; Jamhawi, Abdelqader M.; Islam, Shahidul M.; Ayitou, A. Jean‐Luc (January 2023, Photochemistry and Photobiology)

   Abstract We report the synthesis and photophysical characterization of novel halogenated dipyrrolonaphthyridine‐diones (X₂–DPNDs, X = Cl, Br, and I), as candidates for photodynamic therapy (PDT) application. Apart from the heavy atom‐induced spin‐orbit coupling (SOC) dynamics in the investigated X₂–DPNDs, it was found that the position of the halogen atom (relative to the nitrogen of the pyrrole ring) also influenced the triplet excited state behavior. Interestingly, the faster/efficiency sensitization of³O₂to¹O₂using X₂–DPND correlates with the rate of triplet population,k_ISC >1.6 × 10⁸s⁻¹for I₂–DPNDvs k_ISC >2.9 × 10⁹s⁻¹for Cl₂–DPND and Br₂–DPND (whereτ_ISC = 343 ± 3 ps for I₂–DPND andτ_ISC = 5–6 ns for Cl₂–DPND and Br₂–DPND are the lowest time constants/values for ISC). Furthermore, the heavy atom‐induced SOC in Cl₂–DPND and Br₂–DPND did not lead to a reduction of the corresponding fluorescence (ca75%vs67% for the parent DPND). The attractive photophysical characteristics of Cl₂/Br₂–DPND put them on the landscape as not only promising PDT agents but also as fluorescence probes. The present study is a stepping stone in the development of novel organic photosystems for synergistic photomedicinal applications. 

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4. Supersaturation of even linear cycles in linear hypergraphs

   https://doi.org/10.1017/S0963548320000206  

   Jiang, Tao; Yepremyan, Liana (September 2020, Combinatorics, Probability and Computing)

   Abstract A classical result of Erdős and, independently, of Bondy and Simonovits [3] says that the maximum number of edges in ann-vertex graph not containingC_2k, the cycle of length 2k, isO(n^1+1/k). Simonovits established a corresponding supersaturation result forC_2k’s, showing that there exist positive constantsC,cdepending only onksuch that everyn-vertex graphGwithe(G)⩾Cn^1+1/kcontains at leastc(e(G)/v(G))^2kcopies ofC_2k, this number of copies tightly achieved by the random graph (up to a multiplicative constant). In this paper we extend Simonovits' result to a supersaturation result ofr-uniform linear cycles of even length inr-uniform linear hypergraphs. Our proof is self-contained and includes ther= 2 case. As an auxiliary tool, we develop a reduction lemma from general host graphs to almost-regular host graphs that can be used for other supersaturation problems, and may therefore be of independent interest. 

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5. A role for calcium‐dependent protein kinases in differential CO ₂ ‐ and ABA‐controlled stomatal closing and low CO ₂ ‐induced stomatal opening in Arabidopsis

   https://doi.org/10.1111/nph.17079  

   Schulze, Sebastian; Dubeaux, Guillaume; Ceciliato, Paulo H. O.; Munemasa, Shintaro; Nuhkat, Maris; Yarmolinsky, Dmitry; Aguilar, Jaimee; Diaz, Renee; Azoulay‐Shemer, Tamar; Steinhorst, Leonie; et al (December 2020, New Phytologist)

   Summary Low concentrations of CO₂cause stomatal opening, whereas [CO₂] elevation leads to stomatal closure. Classical studies have suggested a role for Ca²⁺and protein phosphorylation in CO₂‐induced stomatal closing. Calcium‐dependent protein kinases (CPKs) and calcineurin‐B‐like proteins (CBLs) can sense and translate cytosolic elevation of the second messenger Ca²⁺into specific phosphorylation events. However, Ca²⁺‐binding proteins that function in the stomatal CO₂response remain unknown.Time‐resolved stomatal conductance measurements using intact plants, and guard cell patch‐clamp experiments were performed.We isolatedcpkquintuple mutants and analyzed stomatal movements in response to CO₂, light and abscisic acid (ABA). Interestingly, we found thatcpk3/5/6/11/23quintuple mutant plants, but not other analyzedcpkquadruple/quintuple mutants, were defective in high CO₂‐induced stomatal closure and, unexpectedly, also in low CO₂‐induced stomatal opening. Furthermore, K⁺‐uptake‐channel activities were reduced incpk3/5/6/11/23quintuple mutants, in correlation with the stomatal opening phenotype. However, light‐mediated stomatal opening remained unaffected, and ABA responses showed slowing in some experiments. By contrast, CO₂‐regulated stomatal movement kinetics were not clearly affected in plasma membrane‐targetedcbl1/4/5/8/9quintuple mutant plants.Our findings describe combinatorialcpkmutants that function in CO₂control of stomatal movements and support the results of classical studies showing a role for Ca²⁺in this response. 

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