Plants monitor the ambient light conditions using several informational photoreceptors, including red/far-red light absorbing phytochrome. Phytochrome is widely believed to regulate the transcription of light-responsive genes by modulating the activity of several transcription factors. Here we provide evidence that phytochrome significantly changes alternative splicing (AS) profiles at the genomic level in Arabidopsis, to approximately the same degree as it affects steady-state transcript levels. mRNA sequencing analysis revealed that 1,505 and 1,678 genes underwent changes in their AS and steady-state transcript level profiles, respectively, within 1 h of red light exposure in a phytochromedependent manner. Furthermore, we show that splicing factor genes were the main early targets of AS control by phytochrome, whereas transcription factor genes were the primary direct targets of phytochrome-mediated transcriptional regulation. We experimentally validated phytochrome-induced changes in the AS of genes that are involved in RNA splicing, phytochrome signaling, the circadian clock, and photosynthesis. Moreover, we show that phytochrome-induced AS changes of SPA1-RELATED 3, the negative regulator of light signaling, physiologically contributed to promoting photomorphogenesis. Finally, photophysiological experiments demonstrated that phytochrome transduces the signal from its photosensory domain to induce light-dependent AS alterations in the nucleus. Taking these data together, we show that phytochrome directly induces AS cascades in parallel with transcriptional cascades to mediate light responses in Arabidopsis.phytochrome | alternative splicing | light signaling | posttranscriptional regulation | photomorphogenesis

SUMMARYPlants monitor the light environment through informational photoreceptors that include phytochromes. In seedling de-etiolation, phytochrome B (phyB), which is the most important member of the phytochrome family, interacts with transcription factors to regulate gene expression and transduce light signals. In this study, we identified rrc1 (reduced red-light responses in cry1cry2 background 1), an Arabidopsis mutant that is impaired in phyB-mediated light responses. A genetic analysis demonstrated that RRC1 affected light signaling in a phyB-dependent manner. RRC1 encodes an ortholog of the human potential splicing factor SR140. The RRC1 polypeptide contains a C-terminal arginine/serine-rich (RS) domain that is important for the regulation of alternative splicing. Although the complete loss of RRC1 caused pleiotropic developmental abnormalities, the deletion of the RS domain specifically reduced phyB signaling and caused aberrant alternative splicing of several SR protein genes. Moreover, semi-quantitative RT-PCR analysis revealed that the alternative splicing patterns of some of the SR protein genes were altered in a red-light-dependent manner, and that these responses were reduced in both phyB and rrc1 mutants. These findings suggest that the regulation of alternative splicing by the RS domain of RRC1 plays an important role in phyB signal transduction.

Bis(μ-carboxylato-O,O′)-diaquabis(1,10-phenanthroline)dicopper(II) dinitrate tetrahydrates, [Cu(RCOO)(phen)(H2O)]2(NO3)2·4H2O, where R=H, CH3, and (CH3)3C, were prepared and characterized by elemental analyses, electronic spectra, magnetic susceptibilities, and X-ray structure analysis. The magnetic susceptibility data conform to the usual dimer equation. The −2J values are 125 cm−1 for formate, 86 cm−1 for acetate, and 99 cm−1 for 2,2-dimethylpropanoate. The crystal structures of [Cu(HCOO)(phen)(H2O)]2(NO3)2·4H2O (1) and [Cu(CH3COO)(phen)(H2O)]2(NO3)2·4H2O (2) were determined by the single-crystal X-ray diffraction method. The crystallographic data are: Compound 1, monoclinic, I2⁄a, a=18.850(2), b=9.775(2), c=17.752(2) Å, β=99.03(1)°, V=3230.4(8) Å3, Z=4, R=0.055 for 2511 observed unique reflections; Compound 2, monoclinic, C2⁄c, a=18.563(4), b=14.272(5), c=14.126(3) Å, β=106.72(2)°, V=3584(2) Å3, Z=4, R=0.082 for 2092 reflections. The complexes consist of dimeric [Cu(RCOO)(phen)(H2O)]22+)] cations with five-coordinated copper ions linked by two carboxylato ions in a syn-syn bridging arrangement. The Cu···Cu distances are 3.103(2) Å for 1 and 3.063(3) Å for 2.

The spatial resolution of a fast, multichannel, optical recording apparatus has been improved in an attempt to increase the completeness of optical recordings of neuron activity responsible for the Aplysia gill-withdrawal reflex. We developed a new optical apparatus, increasing the number of pixels to 448. Action potential activity from 168 to 192 neurons could be detected. Hence, the number of optically detected neurons increased about 2.5 times in comparison with a previously used 100- or 124-detector optical apparatus. Because optically detected action potential signals were shown to be due to the cell body of a neuron, it was possible to know its position as well as its approximate size. The distribution of the detected active neurons and those neurons that showed an apparent change in spike frequency to the siphon stimulation were determined.

No abstract

Linear correlations with positive slopes have been found for the zero-field splitting parameters (D) and the anisotropic exchange parameters (Dex) vs the singlet–triplet separations (-2J) for [Cu2(O2CR)4(L)2] (R = F3C, FCH2, Cl3C, ClCH2, CH3, H, and C6H5CO) for a wide range of -2J values, ca. 240–650 cm-1. The values of D and Dex for benzoylformate were found to be the highest ever studied. The quality of the linear relations of -2J, Dex and D with the square of the coefficient of 2px(C) of the symmetric HOMO of the bridging carboxylate ions, coeff,2 were found to be in the order, -2J vs coeff2 > Dex vs coeff2 > D vs coeff2. A roughly linear relationship with a negative slope was found for D vs -2J for a system, [Cu2(O2CCMenPh3-n)4(L)2], in which the -2J values cover a relatively small range, ca. 320–370 cm-1.

A crosscorrelational method of action potential trains has been proposed, based on information theory. Two information theoretic quantities, mutual information and channel capacity, were calculated from a pair of action potential trains for detecting a crosscorrelation and estimating synaptic connectivity. The method was compared with conventional ones, using action potential trains obtained by the simulation of a neuron model. This method was shown to have the advantages to more easily find a weak but significant crosscorrelation and to give better estimation of synaptic connectivity independent of the firing probability of a presynaptic neuron.

Novel μ-carboxylato-μ-hydroxo-bridged binuclear copper(II) complexes with 1,10-phenanthroline, [Cu2(OH)(RCOO)(phen)2]X2·H2O (where R = H, X = BF4 (1); R = CH3, X = NO3 (2); R = C2H5, X = NO3 (3)) were prepared and characterized by elemental analyses, electronic spectra, magnetic susceptibilities, and X-ray structure analysis. The magnetic susceptibility data conform to the usual dimer equation. The −2J values are −109 cm−1 for 1, −111 cm−1 for 2, and −109 cm−1 for 3, indicating that a strong ferromagnetic spin coupling exists in these complexes. The crystal structures of 2 and 3 were determined by the single-crystal X-ray diffraction method. The crystallographic data are: Compound 2, monoclinic, P21/n, a = 8.107 (10), b = 18.554 (9), c = 18.616 (7) Å, β = 99.14 (6)°, V = 2765 (6) Å3, Z = 4, R = 0.045 for 3274 observed unique reflections; compound 3, monoclinic, P21/n, a = 7.981 (10), b = 18.352 (8), c = 19.247 (8) Å, β = 97.98 (7)°, V = 2792 (4) Å3, Z = 4, R = 0.047 for 3220 reflections. These complexes have very novel roof-shaped binuclear units with dihedral angles (122.8° for 2 and 122.7 ° for 3) observed between two basal planes of CuO2N2. These small dihedral angles are mainly attributed to the strong ferromagnetic exchange interaction in the present complexes.