Red light-induced structure changes in phytochrome A from Pisum sativum

Red-Shifting B12-Dependent Photoreceptor Protein via Optical Coupling for Inducible Living Materials

Cobalamin (B12)-dependent photoreceptors are gaining traction in materials synthetic biology, especially for optically controlling cell-to-cell adhesion in living materials. However, these proteins are mostly responsive to green light, limiting their deep-tissue applications. Here, we present a general strategy for shifting photoresponse of B12-dependent photoreceptor CarHC from green to red/far-red light via optical coupling. Using thiol-maleimide click chemistry, we labeled cysteine-containing CarHC mutants with SulfoCyanine5 (Cy5), a red light-capturing fluorophore. The resulting photoreceptors not only retained the ability to tetramerize in the presence of adenosylcobalamin (AdoB12), but also gained sensitivity to red light; labeled tetramers disassembled on red light exposure. Using genetically encoded click chemistry, we assembled the red-shifted proteins into hydrogels that degraded rapidly in response to red light. Furthermore, Saccharomyces cerevisiae cells were genetically engineered to display CarHC variants, which, alongside in situ Cy5 labeling, led to living materials that could assemble and disassemble in response to AdoB12 and red light, respectively. These results illustrate the CarHC spectrally tuned by optical coupling as a versatile motif for dynamically controlling cell-to-cell interactions within engineered living materials. Given their prevalence and ecological diversity in nature, this spectral tuning method will expand the use of B12-dependent photoreceptors in optogenetics and living materials.

Controlled Environment Ecosystem: A Cutting-Edge Technology in Speed Breeding

The controlled environment ecosystem is a meticulously designed plant growing chamber utilized for cultivating biofortified crops and microgreens, addressing hidden hunger and malnutrition prevalent in the growing population. The integration of speed breeding within such controlled environments effectively eradicates morphological disruptions encountered in traditional breeding methods such as inbreeding depression, male sterility, self-incompatibility, embryo abortion, and other unsuccessful attempts. In contrast to the unpredictable climate conditions that often prolong breeding cycles to 10-15 years in traditional breeding and 4-5 years in transgenic breeding within open ecosystems, speed breeding techniques expedite the achievement of breeding objectives and F1-F6 generations within 2-3 years under controlled growing conditions. In comparison, traditional breeding may take 5-10 years for plant population line creation, 3-5 years for field trials, and 1-2 years for variety release. The effectiveness of speed breeding in trait improvement and population line development varies across different crops, requiring approximately 4 generations in rice and groundnut, 5 generations in soybean, pea, and oat, 6 generations in sorghum, Amaranthus sp., and subterranean clover, 6-7 generations in bread wheat, durum wheat, and chickpea, 7 generations in broad bean, 8 generations in lentil, and 10 generations in Arabidopsis thaliana annually within controlled environment ecosystems. Artificial intelligence leverages neural networks and algorithm models to screen phenotypic traits and assess their role in diverse crop species. Moreover, in controlled environment systems, mechanistic models combined with machine learning effectively regulate stable nutrient use efficiency, water use efficiency, photosynthetic assimilation product, metabolic use efficiency, climatic factors, greenhouse gas emissions, carbon sequestration, and carbon footprints. However, any negligence, even minor, in maintaining optimal photoperiodism, temperature, humidity, and controlling pests or diseases can lead to the deterioration of crop trials and speed breeding techniques within the controlled environment system. Further comparative studies are imperative to comprehend and justify the efficacy of climate management techniques in controlled environment ecosystems compared to natural environments, with or without soil.

Similarity score for screening phase-retrieved maps in X-ray diffraction imaging - characterization in reciprocal space

X-ray diffraction imaging (XDI) is utilized for visualizing the structures of non-crystalline particles in material sciences and biology. In the structural analysis, phase-retrieval (PR) algorithms are applied to the diffraction amplitude data alone to reconstruct the electron density map of a specimen particle projected along the direction of the incident X-rays. However, PR calculations may not lead to good convergence because of a lack of diffraction patterns in small-angle regions and Poisson noise in X-ray detection. Therefore, the PR calculation is still a bottleneck for the efficient application of XDI in the structural analyses of non-crystalline particles. For screening maps from hundreds of trial PR calculations, we have been using a score and measuring the similarity between a pair of retrieved maps. Empirically, probable maps approximating the particle structures gave a score smaller than a threshold value, but the reasons for the effectiveness of the score are still unclear. In this study, the score is characterized in terms of the phase differences between the structure factors of the retrieved maps, the usefulness of the score in screening the maps retrieved from experimental diffraction patterns is demonstrated, and the effective resolution of similarity-score-selected maps is discussed.

Generation of High-Value Genomic Resource in Rice: A “Subgenomic Library” of Low-Light Tolerant Rice Cultivar Swarnaprabha

Rice is the major staple food crop for more than 50% of the world’s total population, and its production is of immense importance for global food security. As a photophilic plant, its yield is governed by the quality and duration of light. Like all photosynthesizing plants, rice perceives the changes in the intensity of environmental light using phytochromes as photoreceptors, and it initiates a morphological response that is termed as the shade-avoidance response (SAR). Phytochromes (PHYs) are the most important photoreceptor family, and they are primarily responsible for the absorption of the red (R) and far-red (FR) spectra of light. In our endeavor, we identified the morphological differences between two contrasting cultivars of rice: IR-64 (low-light susceptible) and Swarnaprabha (low-light tolerant), and we observed the phenological differences in their growth in response to the reduced light conditions. In order to create genomic resources for low-light tolerant rice, we constructed a subgenomic library of Swarnaprabha that expedited our efforts to isolate light-responsive photoreceptors. The titer of the library was found to be 3.22 × 105 cfu/mL, and the constructed library comprised clones of 4–9 kb in length. The library was found to be highly efficient as per the number of recombinant clones. The subgenomic library will serve as a genomic resource for the Gramineae community to isolate photoreceptors and other genes from rice.

Phylogenetic analysis of phytochrome A gene from Lablab purpureus (L.) Sweet

BACKGROUND

Phytochromes are the best characterized photoreceptors that perceive Red (R)/Far-Red (FR) signals and mediate key developmental responses in plants. It is well established that photoperiodic control of flowering is regulated by PHY A (phytochrome A) gene. So far, the members of PHY A gene family remains unexplored in Lablab purpureus, and therefore, their functions are still not deciphered. PHYA3 is the homologue of phytochrome A and known to be involved in dominant suppression of flowering under long day conditions by downregulating florigens in Glycine max. The present study is the first effort to identify and characterize any photoreceptor gene (PHYA3, in this study) in Lablab purpureus and decipher its phylogeny with related legumes.

RESULTS

PHYA3 was amplified in Lablab purpureus cv GNIB-21 (photo-insensitive and determinate) by utilizing primers designed from GmPHYA3 locus of Glycine max. This study was successful in partially characterizing PHYA3 in Lablab purpureus (LprPHYA3) which is 2 kb longer and belongs to exon 1 region of PHYA3 gene. Phylogenetic analysis of the nucleotide and protein sequences of PHYA genes through MEGA X delineated the conservation and evolution of Lablab purpureus PHYA3 (LprPHYA3) probably from PHYA genes of Vigna unguiculata, Glycine max and Vigna angularis. A conserved basic helix-loop-helix motif bHLH69 was predicted having DNA binding property. Domain analysis of GmPHYA protein and predicted partial protein sequence corresponding to exon-1 of LprPHYA3 revealed the presence of conserved domains (GAF and PAS domains) in Lablab purpureus similar to Glycine max.

CONCLUSION

Partial characterization of LprPHYA3 would facilitate the identification of complete gene in Lablab purpureus utilizing sequence information from phylogenetically related species of Fabaceae. This would allow screening of allelic variants for LprPHYA3 locus and their role in photoperiod responsive flowering. The present study could aid in modulating photoperiod responsive flowering in Lablab purpureus and other related legumes in near future through genome editing.

Cryo-Electron Microscopy of Arabidopsis thaliana Phytochrome A in Its Pr State Reveals Head-to-Head Homodimeric Architecture

Phytochrome photoreceptors regulate vital adaptations of plant development, growth, and physiology depending on the ratio of red and far-red light. The light-triggered Z/E isomerization of a covalently bound bilin chromophore underlies phytochrome photoconversion between the red-absorbing Pr and far-red-absorbing Pfr states. Compared to bacterial phytochromes, the molecular mechanisms of signal propagation to the C-terminal module and its regulation are little understood in plant phytochromes, not least owing to a dearth of structural information. To address this deficit, we studied the Arabidopsis thaliana phytochrome A (AtphyA) at full length by cryo-electron microscopy (cryo-EM). Following heterologous expression in Escherichia coli, we optimized the solvent conditions to overcome protein aggregation and thus obtained photochemically active, near-homogenous AtphyA. We prepared grids for cryo-EM analysis of AtphyA in its Pr state and conducted single-particle analysis. The resulting two-dimensional class averages and the three-dimensional electron density map at 17 Å showed a homodimeric head-to-head assembly of AtphyA. Docking of domain structures into the electron density revealed a separation of the AtphyA homodimer at the junction of its photosensor and effector modules, as reflected in a large void in the middle of map. The overall architecture of AtphyA resembled that of bacterial phytochromes, thus hinting at commonalities in signal transduction and mechanism between these receptors. Our work paves the way toward future studies of the structure, light response, and interactions of full-length phytochromes by cryo-EM.