Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.02.233544v1?rss=1

Authors: Ingole, K. D., Dahale, S. K., BHATTACHARJEE, S.

Abstract:

Rapid adaptation of plants to developmental or physiological cues is facilitated by specific receptors that transduce the signals mostly via post-translational modification (PTM) cascades of downstream partners. Reversible covalent attachment of SMALL UBIQUITIN-LIKE MODIFIER (SUMO), a process termed as SUMOylation, influence growth, development and adaptation of plants to various stresses. Strong regulatory mechanisms maintain the steady-state SUMOylome and mutants with SUMOylation disturbances display mis-primed immunity often with growth consequences. Identity of the SUMO-substrates undergoing SUMOylation changes during defences however remain largely unknown. Here we exploit either the auto-immune property of an Arabidopsis mutant or defense responses induced in wild-type plants against Pseudomonas syringae pv tomato (PstDC3000) to enrich and identify SUMO1-substrates. Our results demonstrate massive enhancement of SUMO1-conjugates due to increased SUMOylation efficiencies during defense responses. Of the 261 proteins we identify, 29 have been previously implicated in immune-associated processes. Role of others expand to diverse cellular roles indicating massive readjustments the SUMOylome alterations may cause during induction of immunity. Overall, our study highlights the complexities of a plant immune network and identifies multiple SUMO-substrates that may orchestrate the signalling.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.07.31.231605v1?rss=1

Authors: Mens, C., Hastwell, A. H., Su, H., Gresshoff, P. M., Mathesius, U., Ferguson, B. J.

Abstract:

Legume plants form a symbiosis with N2-fixing soil rhizobia, resulting in new root organs called nodules that enable N2-fixation. Nodulation is a costly process that is tightly regulated by the host through Autoregulation of Nodulation (AON) and nitrate-dependent regulation of nodulation. Both pathways require legume-specific CLAVATA/ESR-related (CLE) peptides. Nitrogen-induced nodulation-suppressing CLE peptides have not previously been characterised in Medicago truncatula, with only rhizobia-induced MtCLE12 and MtCLE13 identified. Here, we report on novel peptides MtCLE34 and MtCLE35 in nodulation control pathways. The nodulation-suppressing CLE peptides of five legume species were classified into three clades based on sequence homology and phylogeny. This approached identified MtCLE34 and MtCLE35 and four new CLE peptide orthologues of Pisum sativum. Whereas MtCLE12 and MtCLE13 are induced by rhizobia, MtCLE34 and MtCLE35 respond to both rhizobia and nitrate. MtCLE34 was identified as a pseudogene lacking a functional CLE-domain. Overexpression of MtCLE12, MtCLE13 and MtCLE35 inhibits nodulation. Together, our findings indicate that MtCLE12 and MtCLE13 have a distinct role in AON, while MtCLE35 regulates nodule numbers in a rhizobia- and nitrate-dependent manner. MtCLE34 likely had a similar role to MtCLE35 but its function was lost due to a nonsense mutation resulting in the loss of the mature peptide.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.07.31.230813v1?rss=1

Authors: Shipunov, A.

Abstract:

The tribe Plantagineae (Lamiales) is a group of plants with worldwide distribution, notorious for its complicated taxonomy, still unresolved natural history, and a trend of morphologic reduction and simplification. This tribe includes the plantains (Plantago), the small aquatic Littorella, and the northern Andean shrubs Aragoa. Some Plantago lineages exhibit remarkably high diversification rates, which further adds to the complicated classification, and the worldwide distribution of these plants raises numerous questions related to vicariance and dispersal. In this work, we present the broadest phylogeny of the group to date and discuss the evolutionary, morphological, and biogeographical implications of our phylogenetic results, including the description of two new species from the Americas.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.02.233007v1?rss=1

Authors: Podolec, R., Lau, K., Wagnon, T. B., Hothorn, M., Ulm, R.

Abstract:

The plant UV-B photoreceptor UVR8 plays an important role in UV-B acclimation and survival. UV-B absorption by homodimeric UVR8 induces its monomerization and interaction with the E3 ubiquitin ligase COP1, leading ultimately to gene expression changes. UVR8 is inactivated through redimerization, facilitated by RUP1 and RUP2. Here, we describe a novel semi-dominant, hyperactive allele, namely uvr8-17D, that harbors a glycine-101 to serine mutation. UVR8G101S-overexpression led to weak constitutive photomorphogenesis and extreme UV-B responsiveness. UVR8G101S was observed to be predominantly monomeric in vivo and, once activated by UV-B, was not efficiently inactivated. Analysis of a UVR8G101S crystal structure revealed the distortion of a loop region normally involved in stabilization of the UVR8 homodimer. Plants expressing a UVR8 variant combining G101S with the previously described W285A mutation exhibited robust constitutive photomorphogenesis. This work provides further insight into UVR8 activation and inactivation mechanisms, and describes a genetic tool for the manipulation of photomorphogenic responses.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.02.233114v1?rss=1

Authors: Wiedenhoeft, A. C.

Abstract:

One rate-limiting factor in the fight against illegal logging is the lack of powerful, affordable, scalable wood identification tools for field screening. Computer vision wood identification using smartphones fitted with customized imaging peripherals offer a potential solution but to date, such peripherals suffer from one or more weaknesses: low image quality, lack of lighting control, uncontrolled magnification, unknown distortion and spherical aberration, and/or no access to or publication of the system design. To address cost, optical concerns, and open access to designs and parameters, I present the XyloPhone, a 3D printed research quality macroscopic imaging attachment adaptable to any smartphone. It provides a fixed focal distance, exclusion of ambient light, selection of visible light or UV illumination, uses the lens from a commercially available loupe, is powered by a rechargeable external battery, is fully open-sourced, and at a price point of less than 110 USD is a highly affordable tool for the laboratory or the field, and can serve as the foundational hardware for a scalable field deployable computer vision wood identification system.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.07.30.228239v1?rss=1

Authors: Walker, A.-S.

Abstract:

BACKGROUND: Monitoring resistance to Plant Protection Products (PPPs) is crucial for understanding the evolution of resistances in bioagressors, thereby allowing scientists to design sound bioagressor management strategies. Globally, resistance monitoring is implemented by a wide range of actors that fall into three distinct categories: academic, governmental, and private. The purpose of this study was to investigate worldwide diversity in PPP resistance monitoring systems, and to shed light on their different facets. RESULTS: A large survey involving 162 experts from 48 countries made it possible to identify and analyze 250 resistance monitoring systems. Through an in-depth analysis, the features of the different monitoring systems were identified. The main factor differentiating monitoring systems was essentially the capabilities (funding, manpower, technology, etc.) of the actors involved in each system. In most countries, and especially in those with a high Human Development Index, academic, governmental, and private monitoring systems coexist. Overall, systems focus far more on monitoring established resistances than on the detection of emerging resistances. Governmental and private resistance monitoring systems generally have considerable capacities to generate data, whereas academic resistance monitoring systems are more specialized. Governmental actors federate and enrol a wider variety of stakeholders. CONCLUSION: These results suggest that the efficacy of PPP resistance monitoring could be enhanced if the different actors involved in resistance monitoring could pool resources and increase collaborative efforts.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.08.03.233387v1?rss=1

Authors: Luo, C., Wang, S., Ning, K., Chen, Z., Yang, J., Wang, Y., Qi, M., Wang, Q.

Abstract:

Lettuce (Lactuca sativa L.), which belongs to the large Asteraceae (Compositae) family, breeds by sexual reproduction and produce seeds. Actually, lettuce seeds are achenes, which are defined as fruits. However, few studies have described the morphological characteristics of the lettuce achenes, and genes essential for achene development are largely unknown in lettuce. To investigate the gene activity during achene development and determine the possible mechanisms that influence achene development in lettuce, we performed a time-course transcriptome analysis of lettuce achenes. A total of 23,790 expressed genes were detected at the five achene development stages. We investigated the gene expression patterns during achene development and identified the enriched biological processes at the corresponding stages. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology analyses revealed a variety of transcriptomic similarities and differentiation at different achene development stages. Further, transcription factors and phytohormones were found to play important roles during achene development. Finally, we proposed a working model to illustrate the gene expression modules and possible molecular mechanism underlying achene development. Our time-course transcriptome data also provides a foundation for future functional studies to reveal the genetic control of achene development in lettuce.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.07.31.224378v1?rss=1

Authors: Yang, J., BERTOLINI, E., Braud, M., Preciado, J., Chepote, A., Jiang, H., Eveland, A. L.

Abstract:

Inflorescence architecture in cereal crops directly impacts yield potential through regulation of seed number and harvesting ability. Extensive architectural diversity found in inflorescences of grass species is due to spatial and temporal activity and determinacy of meristems, which control the number and arrangement of branches and flowers, and underlie plasticity. Timing of the floral transition is also intimately associated with inflorescence development and architecture, yet little is known about the intersecting pathways and how they are rewired during development. Here, we show that a single mutation in a gene encoding an AP1 A-class MADS-box transcription factor significantly delays flowering time and disrupts multiple levels of meristem determinacy in panicles of the C4 model panicoid grass, Setaria viridis. Previous reports of A-class genes in cereals have revealed extensive functional redundancy, and in panicoid grasses, no associated inflorescence phenotypes have been described. In S. viridis, perturbation of SvFul2, both through chemical mutagenesis and CRISPR/Cas9-based gene editing, converted a normally determinate inflorescence habit to an indeterminate one, and also repressed determinacy in axillary branch and floral meristems. Our analysis of gene networks connected to disruption of SvFul2 identified regulatory hubs at the intersect of floral transition and inflorescence determinacy, providing insights into the optimization of cereal crop architecture.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.07.30.229971v1?rss=1

Authors: Ha, c. v., Nguyen, K. H., Mostofa, M. G., Tran, C. D., Watanabe, Y., Li, W., Osakabe, Y., Sato, M., Toyooka, K., Tanaka, M., Seki, M., Burritt, D. J., Anderson, C., Zhang, R., Tran, S. P.-L.

Abstract:

Cytokinins play an important role in plant stress responses via a multistep signaling pathway, involving the histidine phosphotransfer proteins (HPs). Here, the AHP4 possesses a negative regulatory role in drought response in Arabidopsis thaliana as evidenced by higher survival rates of ahp4 than wild-type (WT) plants under drought, and the down-regulated AHP4 expression in WT during dehydration. Transcriptome analysis of ahp4 and WT plants revealed AHP4-mediated expression of dehydration- and/or abscisic acid (ABA)-responsive genes important for plant drought acclimation. ahp4 plants showed increased wax crystal accumulation in stems, thicker cuticles in leaves, greater sensitivity to exogenous ABA, narrower stomatal apertures, higher leaf temperatures during dehydration, and longer root length under osmotic stress. Additionally, ahp4 plants showed greater photosynthetic efficiency, lower levels of reactive oxygen species, reduced electrolyte leakage and lipid peroxidation, and increased anthocyanin contents under drought. Findings could make editing of AHP4 a promising approach for generating drought-tolerant crops.

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Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.07.30.227447v1?rss=1

Authors: Bianchetti, R., Bellora, N., de Haro, L., Zuccarelli, R., Rosado, D., Freschi, L., Rossi, M., BERMUDEZ, L. F.

Abstract:

Phytochrome-mediated light and temperature perception has been shown to be a major regulator of fruit development. Furthermore, chromatin remodelling via DNA demethylation has been described as a crucial mechanism behind the fruit ripening process; however, the molecular basis underlying the triggering of this epigenetic modification remains largely unknown. Here, through integrative analyses of the methylome, siRNAome and transcriptome of tomato fruits from phyA and phyB1B2 null mutants, we report that PHYB1 and PHYB2 control genome-wide DNA methylation during fruit development. The experimental evidence indicates that PHYB1B2 signal transduction is mediated by the coordinated expression of DNA methylases/demethylases, histone-modifying enzymes and chromatin remodelling factors, resulting in the transcriptional regulation of photosynthetic and ripening-associated genes. This new level of understanding provides insights into the orchestration of epigenetic mechanisms in response to environmental cues affecting agronomical traits.

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