PaperPlayer biorxiv plant biology

Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.13.249367v1?rss=1

Authors: Kozuleva, M., Petrova, A., Milrad, Y., Semenov, A., Ivanov, B., Redding, K. E., Yacoby, I.

Abstract:

Photosynthesis is a vital process, responsible for fixing carbon dioxide, and producing most of the organic matter on the planet. However, photosynthesis has some inherent limitations in utilizing solar energy. Up to a third of the energy absorbed is lost in the reduction of O2 to produce the superoxide radical, which occurs principally within photosystem I (PSI) via the Mehler reaction. Strikingly, the precise location as well as the evolutionary role of the reaction have long been a matter of debate. For decades, O2 reduction was assumed to take place solely in the distal iron-sulfur clusters of PSI rather than within the two asymmetrical cofactor branches. Here we demonstrate that under high irradiance, O2 photoreduction by PSI takes place at the phylloquinone of one of the branches (the A-branch). This conclusion derives from the light dependency of the O2 photoreduction rate constant, and from the high rates of O2 photoreduction in PSI complexes lacking iron-sulfur clusters and in a mutant PSI, in which the lifetime of this phyllosemiquinone state is extended 100-fold. On these grounds, we suggest that the Mehler reaction serves as a release valve, functioning only when needed, under conditions where both the distal iron-sulfur clusters of PSI and the mobile ferredoxin pool are over reduced.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.13.249318v1?rss=1

Authors: Belton, S. P., McCabe, P. F., Ng, C. K.

Abstract:

Cyanobacteria such as Nostoc spp. can form nitrogen-fixing symbioses with a broad range of plant species. Unlike other plant-bacteria symbioses, little is understood about the immunological and developmental signalling events induced by Nostoc cyanobionts (symbiotic cyanobacteria). Here, we used suspension cell cultures to elucidate the early molecular mechanisms underpinning the association between cyanobionts and plants by studying the effects of conditioned medium (CM) from Nostoc punctiforme cultures on plant programmed cell death (PCD), a typical immune response activated during incompatible interactions. We showed that N. punctiforme-CM could suppress PCD induced by a temperature stress. Interestingly, this was preceded by significant transcriptional reprogramming, as evidenced by the differential regulation of a network of defence-associated genes, as well as genes implicated in regulating cell growth and differentiation. This work is the first to show that cyanobionts can regulate PCD in plants and provides a valuable transcriptome resource for the early immunological and developmental signalling events elicited by Nostoc cyanobionts.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.13.246413v1?rss=1

Authors: Martin, R., Qi, T., Zhang, H., Liu, F., King, M., Toth, C., Nogales, E., Staskawicz, B. J.

Abstract:

Plants and animals detect pathogen infection via intracellular nucleotide-binding leucine-rich repeat receptors (NLRs) that directly or indirectly recognize pathogen effectors and activate an immune response. How effector sensing triggers NLR activation remains poorly understood. Here we describe the 3.8 [A] resolution cryo-electron microscopy structure of the activated Roq1, an NLR native to Nicotiana benthamiana with a Toll-like interleukin-1 receptor (TIR) domain, bound to the Xanthomonas effector XopQ. Roq1 directly binds to both the predicted active site and surface residues of XopQ while forming a tetrameric resistosome that brings together the TIR domains for downstream immune signaling. Our results suggest a mechanism for the direct recognition of effectors by NLRs leading to the oligomerization-dependent activation of a plant resistosome and signaling by the TIR domain.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.12.248138v1?rss=1

Authors: Marzec, M., Situmorang, A., Brewer, P., Braszewska-Zalewska, A.

Abstract:

Cytochrome P450 enzymes encoded by MORE AXILLARY GROWTH1 (MAX1)-like genes produce most of the structural diversity of strigolactones during the final steps of strigolactone biosynthesis. The diverse copies of MAX1 in Oryza sativa provide a resource to investigate why plants produce such a wide range of strigolactones. Here we performed in silico analyses of transcription factors and microRNAs that may regulate each rice MAX1, and compared the results with available data about MAX1 expression profiles and genes co-expressed with MAX1 genes. Data suggest that distinct mechanisms regulate the expression of each MAX1. Moreover, there may be novel functions for MAX1 homologues, such as the regulation of flower development or responses to heavy metals. In addition, individual MAX1s could be involved in specific functions, such as the regulation of seed development or wax synthesis in rice. Our analysis reveals potential new avenues of strigolactone research that may otherwise not be obvious.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.12.247924v1?rss=1

Authors: Fabricant, A., Iwata, G. Z., Scherzer, S., Bougas, L., Rolfs, K., Jodko-Władzinska, A., Voigt, J., Hedrich, R., Budker, D.

Abstract:

Upon stimulation, plants elicit electrical signals that can travel within a cellular network analogous to the animal nervous system. It is well-known that in the human brain, voltage changes in certain regions result from concerted electrical activity which, in the form of action potentials (APs), travels within nerve-cell arrays. Electrophysiological techniques like electroencephalography, magnetoencephalography, and magnetic resonance imaging are used to record this activity and to diagnose disorders. In the plant kingdom, two types of electrical signals are observed: all-or-nothing APs of similar amplitudes to those seen in humans and animals, and slow-wave potentials of smaller amplitudes. Sharp APs appear restricted to unique plant species like the "sensitive plant", Mimosa pudica, and the carnivorous Venus flytrap, Dionaea muscipula. Here we ask the question, is electrical activity in the Venus flytrap accompanied by distinct magnetic signals? Using atomic optically pumped magnetometers, biomagnetism in AP-firing traps of the carnivorous plant was recorded. APs were induced by heat stimulation, and the thermal properties of ion channels underlying the AP were studied. The measured magnetic signals exhibit similar temporal behavior and shape to the fast de- and repolarization AP phases. Our findings pave the way to understanding the molecular basis of biomagnetism, which might be used to improve magnetometer-based noninvasive diagnostics of plant stress and disease.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.10.245092v1?rss=1

Authors: Barros, J. A., Magen, S., Lapidot-Cohen, T., Rosental, L., Brotman, Y., Araujo, W. L., Avin-Wittenberg, T.

Abstract:

Autophagy is an evolutionarily conserved mechanism that mediates the degradation of cytoplasmic components in eukaryotic cells. In plants, autophagy has been extensively associated with the recycling of proteins during carbon starvation conditions. Even tough lipids constitute a significant energy reserve, our understanding of the function of autophagy in the management of cell lipid reserves and components remains fragmented. To further investigate the significance of autophagy in lipid metabolism, we performed an extensive lipidomic characterization of Arabidopsis (Arabidopsis thaliana) autophagy mutants (atg) submitted to dark-induced senescence conditions. Our results revealed an altered lipid profile in atg mutants, suggesting that autophagy affects the homeostasis of multiple lipid components under dark-induced senescence. The acute degradation of chloroplast lipids coupled with the differential accumulation of triacylglycerols (TAGs) and plastoglobuli-related transcripts indicates an alternative metabolic reprogramming towards lipid storage in atg mutants. The imbalance of lipid metabolism compromises the production of cytosolic lipid droplets and the regulation of peroxisomal lipid oxidation pathways in atg mutants.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.12.247601v1?rss=1

Authors: Florez, L. M., Scheper, R., Fisher, B., Sutherland, P., Templeton, M., Bowen, J. K.

Abstract:

European canker, caused by the necrotrophic fungal phytopathogen Neonectria ditissima, is one of the most damaging apple diseases worldwide. An understanding of the molecular basis of N. ditissima virulence is currently lacking. Identification of genes with an up-regulation of expression during infection, which are therefore probably involved in virulence, is a first step towards this understanding. Real-time quantitative reverse transcription PCR (qRT-PCR) can be used to identify these candidate virulence genes, but relies on the use of reference genes for relative gene expression data normalisation. However, no report that addresses selecting appropriate fungal reference genes for use in the N. ditissima-apple pathosystem has been published to date. In this study, eight N. ditissima genes were selected as candidate qRT-PCR reference genes for gene expression analysis. A subset of the primers (six) designed to amplify regions from these genes were specific for N. ditissima, failing to amplify PCR products with template from other fungal pathogens present in the apple orchard. The efficiency of amplification of these six primer sets was satisfactory, ranging from 81.8 to 107.53%. Analysis of expression stability when a highly pathogenic N. ditissima isolate was cultured under 10 regimes, using the statistical algorithms geNorm, NormFinder and BestKeeper, indicated that actin and myo-inositol-1-phosphate synthase (mips), or their combination, could be utilised as the most suitable reference genes for normalisation of N. ditissima gene expression. As a test case, these reference genes were used to study expression of three candidate virulence genes during a time course of infection. All three, which shared traits with fungal effector genes, had up-regulated expression in planta compared to in vitro with expression peaking between five and six weeks post inoculation (wpi). Thus, these three genes may well be involved in N. ditissima pathogenicity and are priority candidates for further functional characterization.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.11.246033v1?rss=1

Authors: Zhang, Y.-b., Yang, S.-l., Deng, J., Li, R.-d., Fan, X., Dao, J.-m., Quan, Y.-j., Hussain Bukhari, S. A., Zeng, Z.-h.

Abstract:

Ratooning is an important cultivation practice in sugarcane production around the world, with underground buds on the remaining stalk acting as the source for establishment of a subsequent ratoon crop. However, the optimal depth of cutting during harvest in terms of yield and root growth remains unknown. We carried out a two-year field study to determine the effects of three cutting depths (0, 5 and 10 cm below the surface) ratoon cane root and yield. Results showed that cutting to a depth of 5 cm increased the root fresh weight and root volume by 32-40% and 49-85%, respectively, compared to cutting depths of 0 and 10 cm. Remarkably, cutting to a depth of 5 cm also had a significant effect on the development of fine roots, which is closely linked to cane yield . The effect was particularly noticeable in terms of two root traits, root volume and the surface area of roots with a diameter of 1.0-2.0mm, and root length and the number of root tips in roots with a diameter of 0-0.5mm. As a result, a cutting depth of 5 cm below the surface increased cane yield by 35 and 25% compared to depths of 0 and 10 cm below the surface, respectively. Overall, these findings suggest that a cutting depth of 5 cm is optimal in terms of sugarcane yield, largely due to the enhanced effect on root traits, especially the development of fine roots. These findings will help optimize sugarcane ratoon management and improve the ratoon cycle.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.11.245720v1?rss=1

Authors: Sharma, M., Sharma, M., Jamsheer K, M., Laxmi, A.

Abstract:

The role of jasmonates (JAs) in root growth and development and plants response to external stimuli is already known. However, its role in lateral root (LR) development remains perplexing. Our work identifies methyl jasmonate (MeJA) as a crucial phytohormone in determining the branching angle of Arabidopsis LRs. MeJA inclines the LRs to a more vertical orientation which was dependent on JAR1-COI1-MYC2,3,4 signalling. Our work highlights the dual role of light acting with MeJA in governing the LR angle. Glucose (Glc), produced by light mediated photosynthesis induces wider branching angles. Combining physiological and molecular assays, we reveal that Glc antagonizes the MeJA response via HEXOKINASE1 (HXK1) mediated signalling and by stabilizing JAZ9. Moreover, physiological assays using auxin mutants; binding of MYC2 on the promoters of auxin biosynthetic gene CYP79B2 and LAZY2 and asymmetric distribution of DR5::GFP and PIN2::GFP pinpoints the role of an intact auxin machinery required by MeJA for vertical growth of LRs. We also demonstrate that light perception through PHYTOCHROMES (PHYA and PHYB) and LONG HYPOCOTYL5 (HY5) are indispensable for inducing vertical angles by MeJA. Thus, our investigation highlights antagonism between light and Glc signalling and how they interact with JA-auxin signals to optimize the branching angle of LRs.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.11.243204v1?rss=1

Authors: Kumar Gupta, T., Klumpe, S., Gries, K., Heinz, S., Wietrzynski, W., Ohnishi, N., Niemeyer, J., Schaffer, M., Rast, A., Strauss, M., Plitzko, J. M., Baumeister, W., Rudack, T., Sakamoto, W., Nickelsen, J., Schuller, J. M., Schroda, M., Engel, B. D.

Abstract:

Vesicle-inducing protein in plastids (VIPP1) is essential for the biogenesis and maintenance of thylakoid membranes, which transform light into life. However, it is unknown how VIPP1 performs its vital membrane-shaping function. Here, we use cryo-electron microscopy to determine structures of cyanobacterial VIPP1 rings, revealing how VIPP1 monomers flex and interweave to form basket-like assemblies of different symmetries. Three VIPP1 monomers together coordinate a non-canonical nucleotide binding pocket that is required for VIPP1 oligomerization. Inside the ring's lumen, amphipathic helices from each monomer align to form large hydrophobic columns, enabling VIPP1 to bind and curve membranes. In vivo point mutations in these hydrophobic surfaces cause extreme thylakoid swelling under high light, indicating an essential role of VIPP1 lipid binding in resisting stress-induced damage. Our study provides a structural basis for understanding how the oligomerization of VIPP1 drives the biogenesis of thylakoid membranes and protects these life-giving membranes from environmental stress.

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