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In flowering plants, the female gametophyte controls pollen tube reception immediately before fertilization and regulates seed development immediately after fertilization, although the controlling mechanisms remain poorly understood. Previously, we showed that LORELEI (LRE), which encodes a putative glycosylphosphatidylinositol-anchored membrane protein, is critical for pollen tube reception by the female gametophyte before fertilization and the initiation of seed development after fertilization. Here, we show that LRE is expressed in the synergid, egg, and central cells of the female gametophyte and in the zygote and proliferating endosperm of the Arabidopsis (Arabidopsis thaliana) seed. Interestingly, LRE expression in the developing seeds was primarily from the matrigenic LRE allele, indicating that LRE expression is imprinted. However, LRE was biallelically expressed in 8-d-old seedlings, indicating that the patrigenic allele does not remain silenced throughout the sporophytic generation. Regulation of imprinted LRE expression is likely novel, as LRE was not expressed in pollen or pollen tubes of mutants defective for MET1, DDM1, RNA-dependent DNA methylation, or MSI-dependent histone methylation. Additionally, the patrigenic LRE allele inherited from these mutants was not expressed in seeds. Surprisingly, and contrary to the predictions of the parental conflict hypothesis, LRE promotes growth in seeds, as loss of the matrigenic but not the patrigenic LRE allele caused delayed initiation of seed development. Our results showed that LRE is a rare imprinted gene that functions immediately after double fertilization and supported the model that a passage through the female gametophyte establishes monoalleleic expression of LRE in seeds and controls early seed development.

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26A signaling complex comprising members of the LORELEI (LRE)-LIKE GPI-27 anchored protein (LLG) and Catharanthus roseus RECEPTOR-LIKE KINASE 1-LIKE 28 (CrRLK1L) families perceive RAPID ALKALINIZATION FACTOR (RALF) peptides and 29 regulate growth, development, reproduction, and immunity in Arabidopsis thaliana. 30 Duplications in each component, which potentially could generate thousands of 31 combinations of this signaling complex, are also evident in other angiosperms. 32 Widespread duplication in angiosperms raises the question what evolutionary 33 mechanisms underlie the expansion and retention of these gene families, as duplicated 34 genes are typically rendered non-functional. As genetic and genomic resources make it 35 a tractable model system, here we investigated this question using LLG gene family 36 evolution and function in Brassicaceae. We first established that the LLG homologs in the 37 Brassicaceae resulted from duplication events that pre-date the divergence of species in 38 this family. Complementation of vegetative phenotypes in llg1 by LRE, LLG2, and LLG3 39 showed that the molecular functions of LLG homologs in A. thaliana are conserved. We 40 next tested the possibility that differences in gene expression (regulatory 41 subfunctionalization), rather than functional divergence, played a role in retention of these 42 duplicated genes. For this, we examined the function and expression of LRE and LLG1 43 in A. thaliana and their single copy ortholog in Cleome violacea (Clevi LRE/LLG1), a 44 representative species outside the Brassicaceae, but from the same order (Brassicales). 45 We showed that expression of LLG1 and LRE did not overlap in A. thaliana and that Clevi-46 LRE/LLG1 expression in C. violacea encompassed all the expression domains of A. 47 thaliana LRE + LLG1. Still, complementation experiments showed that LLG1 rescued 48 reproductive phenotypes in lre and that Clevi LRE/LLG1 rescued both vegetative and 49 reproductive phenotypes in llg1 and lre. Additionally, we found that expression of LLG2 50 and LLG3 in A. thaliana have also diverged from the expression of their corresponding 51 single copy ortholog (Clevi LLG2/LLG3) in C. violacea. Our findings demonstrated how 52 regulatory subfunctionalization, rather than functional divergence, underlies the retention 53 of the LLG gene family in Brassicaceae. Our findings on the regulatory divergence and 54 functional conservation provide an experimental framework to characterize the 55 combinatorial assembly and function of this critical plant cell signaling complex. 56 57pathogen-associated molecular patterns (PAMPs) flagellin and elongation factor thermo 85 unstable (EF-TU) via the immunogenic epitopes flg22 and elf18, respectively. In this 86 context, RALF23 binds to FER-LLG1 to suppress the scaffolding function of FER, thereby 87 inhibiting ROS production and immunity [16, 17]. 88In A. thaliana, the GPI-anchored protein (GPI-AP), receptor kinase, and small CRP 89 components of the trimeric CrRLK1L-LLG-RALF signaling complex are ...

Interstellar dust grain growth in dense clouds and protoplanetary disks, even moderate, affects the observed interstellar ice profiles as soon as a significant fraction of dust grains is in the size range close to the wave vector at the considered wavelength. The continuum baseline correction made prior to analysing ice profiles influences the subsequent analysis and hence the estimated ice composition, typically obtained by band fitting using thin film ice mixture spectra. We explore the effect of grain growth on the spectroscopic profiles of ice mantle constituents, focusing particularly on carbon dioxide, with the aim of understanding how it can affect interstellar ice mantle spectral analysis and interpretation. Using the Discrete Dipole Approximation for Scattering and Absorption of Light, the mass absorption coefficients of several distributions of grains -composed of ellipsoidal silicate cores with water and carbon dioxide ice mantles -are calculated. A few models also include amorphous carbon in the core and pure carbon monoxide in the ice mantle. We explore the evolution of the size distribution starting in the dense core phase in order to simulate the first steps of grain growth up to three microns in size. The resulting mass absorption coefficients are injected into RADMC-3D radiative transfer models of spherical dense core and protoplanetary disk templates to retrieve the observable spectral energy distributions. Calculations are performed using the full scattering capabilities of the radiative transfer code. We then focus on the particularly relevant calculated profile of the carbon dioxide ice band at 4.27 𝜇m. The carbon dioxide antisymmetric stretching mode profile is a meaningful indicator of grain growth. The observed profile toward dense cores with the Infrared space observatory and Akari satellites already showed profiles possibly indicative of moderate grain growth. The observation of true protoplanetary disks at high inclination with the JWST should present distorted profiles that will allow constraints to be placed on the extent of dust growth. The more evolved the dust size distribution, the more the extraction of the ice mantle composition will require both understanding and taking into account grain growth.

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Recent experimental work revealed that the lifetime of the S3 state of protonated 7-azaindole is about ten times slower than that of protonated 6-azaindole. We simulated the nonradiative decay pathways of these molecules using trajectory surface hopping dynamics after photoexcitation into S3 to elucidate the reason for this difference. Both isomers mainly follow a common pp* relaxation pathway involving multiple state crossings while coming down from S3 to S1 in the subpicosecond time scale. However, the simulations reveal that the excited-state topographies are such that while the 6-isomer can easily access the region of nonadiabatic transitions, the internal conversion of the 7-isomer is delayed by a pre-Dewar bond formation with a boat conformation.