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Background and aimsCultured cell suspensions have been the preferred model to study the apoplast as well as to monitor metabolic and cell cycle-related changes. Previous work showed that methyl jasmonate (MeJA) inhibits leaf growth in a CORONATINE INSENSITIVE 1 (COI1)-dependent manner, with COI1 being the jasmonate (JA) receptor. Here, the effect of COI1 overexpression on the growth of stably transformed arabidopsis cell cultures is described.MethodsTime-course experiments were carried out to analyse gene expression, and protein and metabolite levels.Key resultsBoth MeJA treatment and the overexpression of COI1 modify growth, by altering cell proliferation and expansion. DNA content as well as transcript patterns of cell cycle and cell wall remodelling markers were altered. COI1 overexpression also increases the protein levels of OLIGOGALACTURONIDE OXIDASE 1, BETA-GLUCOSIDASE/ENDOGLUCANASES and POLYGALACTURONASE INHIBITING PROTEIN2, reinforcing the role of COI1 in mediating defence responses and highlighting a link between cell wall loosening and growth regulation. Moreover, changes in the levels of the primary metabolites alanine, serine and succinic acid of MeJA-treated Arabidopsis cell cultures were observed. In addition, COI1 overexpression positively affects the availability of metabolites such as β-alanine, threonic acid, putrescine, glucose and myo-inositol, thereby providing a connection between JA-inhibited growth and stress responses.ConclusionsThis study contributes to the understanding of the regulation of growth and the production of metabolic resources by JAs and COI1. This will have important implications in dissecting the complex relationships between hormonal and cell wall signalling in plants. The work also provides tools to uncover novel mechanisms co-ordinating cell division and post-mitotic cell expansion in the absence of organ developmental control.

Summary: Phytochemicals are used often in vitro and in vivo in cancer research. The plant hormones jasmonates (JAs) control the synthesis of specialized metabolites through complex regulatory networks. JAs possess selective cytotoxicity in mixed populations of cancer and normal cells.Here, direct incubation of leaf explants from the non‐medicinal plant Arabidopsis thaliana with human breast cancer cells, selectively suppresses cancer cell growth. High‐throughput LC‐MS identified Arabidopsis metabolites. Protein and transcript levels of cell cycle regulators were examined in breast cancer cells.A synergistic effect by methyljasmonate (MeJA) and by compounds upregulated in the metabolome of MeJA‐treated Arabidopsis leaves, on the breast cancer cell cycle, is associated with Cell Division Cycle 6 (CDC6), Cyclin‐dependent kinase 2 (CDK2), Cyclins D1 and D3, indicating that key cell cycle components mediate cell viability reduction. Bioactives such as indoles, quinolines and cis‐(+)‐12‐oxophytodienoic acid, in synergy, could act as anticancer compounds.Our work suggests a universal role for MeJA‐treatment of Arabidopsis in altering the DNA replication regulator CDC6, supporting conservation, across kingdoms, of cell cycle regulation, through the crosstalk between the mechanistic target of rapamycin, mTOR and JAs. This study has important implications for the identification of metabolites with anti‐cancer bioactivities in plants with no known medicinal pedigree and it will have applications in developing disease treatments [ABSTRACT FROM AUTHOR]

Yams (Dioscorea spp.) host a diverse range of badnaviruses (genus Badnavirus, family Caulimoviridae). The first complete genome sequence of Dioscorea bacilliform RT virus 3 (DBRTV3), which belongs to the monophyletic species group K5, is described. This virus is most closely related to Dioscorea bacilliform SN virus (DBSNV, group K4) based on a comparison of genome sequences. Recombination analysis identified a unique recombination event in DBRTV3, with DBSNV likely to be the major parent and Dioscorea bacilliform AL virus (DBALV) the minor parent, providing the first evidence for recombination in yam badnaviruses. This has important implications for yam breeding programmes globally. [ABSTRACT FROM AUTHOR]

The STOREKEEPER (STK) family of DNA-binding proteins work as transcription factors and the ectopic expression of two stk-like genes from Arabidopsis thaliana, stk01 (At1g61730) and stk03 (At4g00238), in tobacco increased the number of vegetative internodes and promoted plant and leaf size, stem diameter and sturdiness. The development of these plants started with rosette formation while pronounced shoot elongation and flowering was delayed. Moreover, when the STK01 and STK03 proteins were fused to the Herpes Simplex Virus VP16 transcriptional activation domain and expressed in tobacco the vigorous storekeeper-phenotype did not appear indicating that transgenic STK-like proteins in part worked as repressors of tobacco reproductive development. Furthermore, Yeast Two-Hybrid screenings proved that STK01 and STK03 can form homodimers and heterodimers with further members of the STKlike family. Therefore, we assume that interactions between transgenic Arabidopsis STKs and resident tobacco STKs could have contributed to the observed developmental changes in transgenic tobacco. Our findings open up promising applications for overexpression of stk-like genes in crops that benefit from increased sturdiness and vegetative organ development, such as tobacco in molecular farming approaches, biomass-based energy crops and medicinal plants that produce bioactive compounds in leaves. [ABSTRACT FROM AUTHOR]

Potyviruses (genus Potyvirus; family Potyviridae) are widely distributed and represent one of the most economically important genera of plant viruses. Therefore, their accurate detection is a key factor in developing efficient control strategies. However, this can sometimes be problematic particularly in plant species containing high amounts of polysaccharides and polyphenols such as yam (Dioscorea spp.). Here, we report the development of a reliable, rapid and cost-effective detection method for the two most important potyviruses infecting yam based on reverse transcription-recombinase polymerase amplification (RT-RPA). The developed method, named 'Direct RT-RPA', detects each target virus directly from plant leaf extracts prepared with a simple and inexpensive extraction method avoiding laborious extraction of high-quality RNA. Direct RT-RPA enables the detection of virus-positive samples in under 30 min at a single low operation temperature (37 °C) without the need for any expensive instrumentation. The Direct RT-RPA tests constitute robust, accurate, sensitive and quick methods for detection of potyviruses from recalcitrant plant species. The minimal sample preparation requirements and the possibility of storing RPA reagents without cold chain storage, allow Direct RT-RPA to be adopted in minimally equipped laboratories and with potential use in plant clinic laboratories and seed certification facilities worldwide., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)