Extracellular matrix in plants and animals: hooks and locks for viruses

Open Access Journal; Published online: 12 Sept 2017The extracellular matrix (ECM) of animal and plants cells plays important roles in viral diseases. While in animal cells extracellular matrix components can be exploited by viruses for recognition, attachment and entry, the plant cell wall acts as a physical barrier to viral entry and adds a higher level of difficulty to intercellular movement of viruses. Interestingly, both in plant and animal systems, ECM can be strongly remodeled during virus infection, and the understanding of remodeling mechanisms and molecular players offers new perspectives for therapeutic intervention. This review focuses on the different roles played by the ECM in plant and animal hosts during virus infection with special emphasis on the similarities and differences. Possible biotechnological applications aimed at improving viral resistance are discussed

Prosystemin overexpression induces transcriptional modifications of defense-related and receptor-like kinase genes and reduces the susceptibility to Cucumber mosaic virus and its satellite RNAs in transgenic tomato plants

Open Access JournalSystemin is a plant signal peptide hormone involved in the responses to wounding and insect damage in the Solanaceae family. It works in the same signaling pathway of jasmonic acid (JA) and enhances the expression of proteinase inhibitors. With the aim of studying a role for systemin in plant antiviral responses, a tomato (Solanum lycopersicum) transgenic line overexpressing the prosystemin cDNA, i.e. the systemin precursor, was inoculated with Cucumber mosaic virus (CMV) strain Fny supporting either a necrogenic or a non-necrogenic satellite RNA (satRNA) variant. Transgenic plants showed reduced susceptibility to both CMV/satRNA combinations. While symptoms of the non-necrogenic inoculum were completely suppressed, a delayed onset of lethal disease occurred in about half of plants challenged with the necrogenic inoculum. RT-qPCR analysis showed a correlation between the systemin-mediated reduced susceptibility and the JA biosynthetic and signaling pathways (e.g. transcriptional alteration of lipoxygenase D and proteinase inhibitor II). Moreover, transgenically overexpressed systemin modulated the expression of a selected set of receptor-like protein kinase (RLK) genes, including some playing a known role in plant innate immunity. A significant correlation was found between the expression profiles of some RLKs and the systemin-mediated reduced susceptibility to CMV/satRNA. These results show that systemin can increase plant defenses against CMV/satRNA through transcriptional reprogramming of diverse signaling pathways

Metabolic profiles of six African cultivars of cassava (Manihot esculenta Crantz) highlight bottlenecks of root yield

Open Access Article; Published online: 17 Jan 2020Cassava is an important staple crop in sub‐Saharan Africa, due to its high productivity even on nutrient poor soils. The metabolic characteristics underlying this high productivity are poorly understood including the mode of photosynthesis, reasons for the high rate of photosynthesis, the extent of source/sink limitation, the impact of environment, and the extent of variation between cultivars. Six commercial African cassava cultivars were grown in a greenhouse in Erlangen, Germany, and in the field in Ibadan, Nigeria. Source leaves, sink leaves, stems and storage roots were harvested during storage root bulking and analyzed for sugars, organic acids, amino acids, phosphorylated intermediates, minerals, starch, protein, activities of enzymes in central metabolism and yield traits. High ratios of RuBisCO:phosphoenolpyruvate carboxylase activity support a C3 mode of photosynthesis. The high rate of photosynthesis is likely to be attributed to high activities of enzymes in the Calvin–Benson cycle and pathways for sucrose and starch synthesis. Nevertheless, source limitation is indicated because root yield traits correlated with metabolic traits in leaves rather than in the stem or storage roots. This situation was especially so in greenhouse‐grown plants, where irradiance will have been low. In the field, plants produced more storage roots. This was associated with higher AGPase activity and lower sucrose in the roots, indicating that feedforward loops enhanced sink capacity in the high light and low nitrogen environment in the field. Overall, these results indicated that carbon assimilation rate, the K battery, root starch synthesis, trehalose, and chlorogenic acid accumulation are potential target traits for genetic improvement

Transcriptome and metabolome profiling identify factors potentially involved in pro-vitamin A accumulation in cassava landraces

Open Access ArticleCassava (Manihot esculenta Crantz) is a predominant food security crop in several developing countries. Its storage roots, rich in carbohydrate, are deficient in essential micronutrients, including provitamin A carotenoids. Increasing carotenoid content in cassava storage roots is important to reduce the incidence of vitamin A deficiency, a public health problem in sub-Saharan Africa. However, cassava improvement advances slowly, mainly due to limited information on the molecular factors influencing β-carotene accumulation in cassava. To address this problem, we performed comparative transcriptomic and untargeted metabolic analyses of roots and leaves of eleven African cassava landraces ranging from white to deep yellow colour, to uncover regulators of carotenoid biosynthesis and accumulation with conserved function in yellow cassava roots. Sequence analysis confirmed the presence of a mutation, known to influence β-carotene content, in PSY transcripts of deep yellow but not of pale yellow genotypes. We identified genes and metabolites with expression and accumulation levels significantly associated with β-carotene content. Particularly an increased activity of the abscisic acid catabolism pathway together with a reduced amount of L-carnitine, may be related to the carotenoid pathway flux, higher in yellow than in white storage roots. In fact, NCED_3.1 was specifically expressed at a lower level in all yellow genotypes suggesting that it could be a potential target for increasing carotenoid accumulation in cassava. These results expand the knowledge on metabolite compositions and molecular mechanisms influencing carotenoid biosynthesis and accumulation in cassava and provide novel information for biotechnological applications and genetic improvement of cassava with high nutritional values

EpiCass and CassavaNet4Dev advanced bioinformatics workshop

Open Access ArticleEpiCass and CassavaNet4Dev are collaborative projects funded by the Swedish Research Council between the Swedish University of Agriculture (SLU) and the International Institute of Tropical Agriculture (IITA). The projects aim to investigate the influence of epigenetic changes on agricultural traits such as yield and virus resistance while also providing African students and researchers with advanced bioinformatics training and opportunities to participate in big data analysis events. The first advanced bioinformatics training workshop took place from May 16th to May 18th, 2022, followed by an online mini-symposium titled "Epigenetics and crop improvement" on May 19th. The symposium featured international speakers covering a wide range of topics related to plant epigenetics, cassava viral diseases, and cassava breeding strategies. A new online and on-site teaching concept was developed for the three-day workshop to ensure maximum student participation across Western, Eastern, and Southern Africa. Initially planned in Nigeria, Kenya, Ethiopia, Tanzania, and Zambia, the workshop ultimately focused on Nigeria, Kenya, and Ethiopia due to a lack of qualified candidates in the other countries. Each classroom hosted 20 to 25 students, with at least one bioinformatician present for support. The classrooms were connected via video conferencing, whereas teachers located in different places in Africa and Europe joined the video stream to conduct teaching sessions. The workshop was divided into theoretical classes and hands-on sessions, where participants could run data analysis with support from online teachers and local bioinformaticians. To enable participants to run guided, CPU and RAM-intensive data analysis workflows and overcome local computing and internet access restrictions, a system of virtual machines (VMs) hosted in the cloud was developed. The teaching platform provided teaching and exercise materials to support the use of the VMs. Although some students could not run heavy data analysis workflows due to unforeseen restrictions in the cloud, these issues were solved. All participants had the opportunity to run the analysis steps independently in the cloud using the protocols hosted on the teaching platform

Auxin signaling and vascular cambium formation enables storage metabolism in cassava tuberous roots

Open Access Article; Published online: 13 Mar 2021Cassava storage roots are among the most important root crops worldwide and represent one of the most consumed staple foods in Sub-Saharan Africa. The vegetatively propagated tropical shrub can form many starchy tuberous roots from its stem. These storage roots are formed through the activation of secondary root growth processes. However, the underlying genetic regulation of storage root development is largely unknown. Here we report on distinct structural and transcriptional changes occurring during the early phases of storage root development. A pronounced increase in auxin-related transcripts and the transcriptional activation of secondary growth factors, as well as a decrease in gibberellin-related transcripts was observed during the early stages of secondary root growth. This was accompanied by increased cell wall biosynthesis, increased most notably during the initial xylem expansion within the root vasculature. Starch storage metabolism was activated only after the formation of the vascular cambium. The formation of nonlignified xylem parenchyma cells and the activation of starch storage metabolism coincided with increased expression of the KNOX/BEL genes KNAT1, PENNYWISE and POUND-FOOLISH, indicating their importance for proper xylem parenchyma function

A Family of Plasmodesmal Proteins with Receptor-Like Properties for Plant Viral Movement Proteins

Plasmodesmata (PD) are essential but poorly understood structures in plant cell walls that provide symplastic continuity and intercellular communication pathways between adjacent cells and thus play fundamental roles in development and pathogenesis. Viruses encode movement proteins (MPs) that modify these tightly regulated pores to facilitate their spread from cell to cell. The most striking of these modifications is observed for groups of viruses whose MPs form tubules that assemble in PDs and through which virions are transported to neighbouring cells. The nature of the molecular interactions between viral MPs and PD components and their role in viral movement has remained essentially unknown. Here, we show that the family of PD-located proteins (PDLPs) promotes the movement of viruses that use tubule-guided movement by interacting redundantly with tubule-forming MPs within PDs. Genetic disruption of this interaction leads to reduced tubule formation, delayed infection and attenuated symptoms. Our results implicate PDLPs as PD proteins with receptor-like properties involved the assembly of viral MPs into tubules to promote viral movement