Transcriptome studies of Illumina RNA-Seq datasets of different Arabidopsis thaliana natural accessions and T-DNA mutants revealed the presence of two virus-like RNA sequences which showed the typical two-segmented genome characteristics of a comovirus. This comovirus did not induce any visible symptoms in infected A. thaliana plants cultivated under standard laboratory conditions. Hence it was named Arabidopsis latent virus 1 (ArLV1). Virus infectivity in A. thaliana plants was confirmed by quantitative reverse transcription polymerase chain reaction, transmission electron microscopy and mechanical inoculation. Arabidopsis latent virus 1 can also mechanically infect Nicotiana benthamiana, causing distinct mosaic symptoms. A bioinformatics investigation of A. thaliana RNA-Seq repositories, including nearly 6500 Sequence Read Archives (SRAs) in the NCBI SRA database, revealed the presence of ArLV1 in 25% of all archived natural A. thaliana accessions and in 8.5% of all analyzed SRAs. Arabidopsis latent virus 1 could also be detected in A. thaliana plants collected from the wild. Arabidopsis latent virus 1 is highly seed-transmissible with up to 40% incidence on the progeny derived from infected A. thaliana plants. This has probably led to a worldwide distribution in the model plant A. thaliana with as yet unknown effects on plant performance in a substantial number of studies.

Constant exposure to various environmental and endogenous stresses can cause structural DNA damage, resulting in genome instability. Higher eukaryotic cells deploy conserved DNA repair systems, which include various DNA repair pathways, to maintain genome stability. Homologous recombination (HR), one of these repair pathways, involves multiple proteins. BRCA2, one of the proteins in the HR pathway, is of substantial research interest in humans because it is an oncogene. However, the study of this gene is limited due to the lack of availability of homozygous BRCA2 -knockout mutants in mammals, which results in embryonic lethality. Arabidopsis thaliana has two copies of the BRCA2 homologs: BRCA2A and BRCA2B . Therefore, the single mutants remain nonlethal and fertile in Arabidopsis. The BRCA2A homolog, which plays a significant role in the HR pathway of germline cells and during the defense response, is well-studied in Arabidopsis. Our study focuses on the functional characterization of the BRCA2B homolog in the somatic cells of Arabidopsis, using the homozygous ΔBRCA2B mutant line. The phenotypic differences of ΔBRCA2B mutants were characterized and compared with wild Arabidopsis plants. The role of BRCA2B in spontaneous somatic HR (SHR) was studied using the ΔBRCA2B -gus detector line. ΔBRCA2B plants have a 6.3-fold lower SHR frequency than the control detector plants. Expression of four other HR pathway genes, including BRE, BRCC36A, RAD50 , and RAD54, was significantly reduced in ΔBRCA2B mutants. Thus, our findings convey that the BRCA2B homolog plays an important role in maintaining spontaneous SHR rates and has a direct or indirect regulatory effect on the expression of other HR-related genes.

The response of plants to waterlogging stress is a complex process, with ethylene playing a crucial role as a signaling molecule. However, it remains unclear how ethylene is initially triggered in response to waterlogging stress when plants are continuously waterlogged for less than 12 hours. Here, we have shown that ethylene-induced autophagy leads to the degradation of damaged mitochondria (the main organelles producing reactive oxygen species (ROS)) to reduce ROS production during oxidative stress in Arabidopsis thaliana, which improves the survival rate of root cells in the early stages of waterlogging stress. Waterlogging stress activated ethylene-related genes, including ACO2, ACS2, ERF72, ERF73, and EIN3, and ethylene content of plants increased significantly within 24 h of continuous waterlogging. As stress duration increased, increased amounts of ROS accumulated in Arabidopsis thaliana roots, and the activity of antioxidant enzymes initially increased and then decreased. Concurrently, the level of ethylene-induced autophagy, which participates in antioxidant defense, is higher in wild-type plants than in the octuple acs mutant cs16651 (acs2-1/acs4-1/acs5-2/acs6-1/acs7-1/acs9-1/amiRacs8acs11). Exogenous application of 1-aminocyclopropanecarboxylic acid (ACC), resulted in a more pronounced manifestation of autophagy in the stele of Arabidopsis roots. Compared with the waterlogging treatment group or the ACC treatment group, the waterlogging + ACC treatment can induce autophagy to occur earlier and expand the autophagic range to the epidermis of Arabidopsis thaliana roots. Overall, our results provide insight into the important role of ethylene-induced autophagy in enhancing the antioxidative capacity of Arabidopsis thaliana during the early stages of waterlogging stress. Furthermore, we suggest ethylene as a potential candidate for mitigating the deleterious effects caused by waterlogging in Arabidopsis thaliana.

4,8-dihydroxy-l-tetralone (4,8-DHT) is an allelochemical isolated from the outer bark of <i>Carya cathayensis</i> that acts as a plant growth inhibitor. In order to explore the mechanism of 4,8-DHT inhibiting weed activity, we treated three species of <i>Digitaria sanguinalis</i>, <i>Arabidopsis thaliana,</i> and <i>Poa annua</i> with different concentrations of 4,8-DHT and performed phenotype observation and transcriptome sequencing. The results showed that with an increase in 4,8-DHT concentration, the degree of plant damage gradually deepened. Under the same concentration of 4,8-DHT, the damage degree of leaves and roots of <i>Digitaria sanguinalis</i> was the greatest, followed by <i>Arabidopsis thaliana</i>, while <i>Poa annua</i> had the least damage, and the leaves turned slightly yellow. Transcriptome data showed that 24536, 9913, and 1662 differentially expressed genes (DEGs) were identified in <i>Digitaria sanguinalis</i>, <i>Arabidopsis thaliana,</i> and <i>Poa annua</i>, respectively. These DEGs were significantly enriched in photosynthesis, carbon fixation, glutathione metabolism, phenylpropanoid biosynthesis, and oxidative phosphorylation pathways. In addition, DEGs were also enriched in plant hormone signal transduction and the MAPK signal pathway in <i>Arabidopsis thaliana</i>. Further analysis showed that after 4,8-DHT treatment, the transcript levels of photosynthesis PSI- and PSII-related genes, LHCA/B-related genes, Rubisco, and PEPC were significantly decreased in <i>Digitaria sanguinalis</i> and <i>Arabidopsis thaliana</i>. At the same time, the transcription levels of genes related to glutathione metabolism and the phenylpropanoid biosynthesis pathway in <i>Digitaria sanguinalis</i> were also significantly decreased. However, the expression of these genes was upregulated in <i>Arabidopsis thaliana</i> and <i>Poa annua</i>. These indicated that 4,8-DHT affected the growth of the three plants through different physiological pathways, and then played a role in inhibiting plant growth. Simultaneously, the extent to which plants were affected depended on the tested plants and the content of 4,8-DHT. The identification of weed genes that respond to 4,8-DHT has helped us to further understand the inhibition of plant growth by allelochemicals and has provided a scientific basis for the development of allelochemicals as herbicides.

Arabidopsis H3K9 methyltransferases directly interact with ASYMMETRIC LEAVES1 (AS1) and AS2 to repress KNOTTED-LIKE FROM ARABIDOPSIS THALIANA 1 (KNAT1) and KNAT2 in leaf development.

Mandelonitrile is a nitrogen-containing compound, considered an essential secondary metabolite. Chemically, it is a cyanohydrin derivative of benzaldehyde, with relevant functions in different physiological processes including defense against phytophagous arthropods. So far, procedures for detecting mandelonitrile have been effectively applied in cyanogenic plant species such as Prunus spp. Nevertheless, its presence in Arabidopsis thaliana, considered a non-cyanogenic species, has never been determined. Here, we report the development of an accurate protocol for mandelonitrile quantification in A. thaliana within the context of A. thaliana–spider mite interaction. First, mandelonitrile was isolated from Arabidopsis rosettes using methanol; then, it was derivatized by silylation to enhance detection and, finally, it was quantified using gas chromatography–mass spectrometry. The selectivity and sensitivity of this method make it possible to detect low levels of mandelonitrile (LOD 3 ppm) in a plant species considered non-cyanogenic that, therefore, will have little to no cyanogenic compounds, using a small quantity of starting material (≥100 mg).

Resumen La alfalfa (Medicago sativa) es originaria de Asia Central, esta leguminosa se siembra en todo México, contribuye a la regeneración de la fertilidad del suelo, además, su elevado contenido de proteínas y aminoácidos ayuda a la reducción de costos de producción de carne y leche. El objetivo del presente trabajo fue valuar diferentes densidades de siembra y la efectividad del extracto a base de exudados de alfalfa sobre plántulas de Arabidopsis thaliana (L.) Heynh. Se empleó semilla de alfalfa variedad San Miguelito y Belleza Verde. La siembra se estableció en cajas Petri en el Tecnológico Nacional de México Campus Roque en noviembre de 2018. Se utilizaron tres densidades de siembra 3, 6 y 9 kg ha-1. Todas las variables se sometieron a un análisis de varianza y una comparación de medias, con el paquete SAS 9.0. El desarrollo radicular de la alfalfa fue afectado por la densidad de siembra, en particular al desarrollo de raíces laterales y presencia de pelos radicales, no así para la longitud de la raíz. La densidad de siembra con mayor desarrollo radicular fue con los 9 kg ha-1. Los exudados de la alfalfa presentaron un efecto antagónico muy marcado sobre Arabidopsis thaliana al reducir su crecimiento, este efecto fue más alto para la densidad de 9 kg ha-1. Una concentración de 50% o más de exudados de alfalfa disminuye el crecimiento hasta llegar a la muerte de esta Arabidopsis thaliana. | Abstract Alfalfa (Medicago sativa) is native to Central Asia, this legume is sown throughout Mexico, contributes to the regeneration of soil fertility, in addition, its high content of proteins and amino acids helps reduce costs of meat and milk production. The objective of this study was to evaluate different sowing densities and the effectiveness of the extract based on alfalfa exudates on seedlings of Arabidopsis thaliana (L.) Heynh. Seeds of the alfalfa varieties San Miguelito and Belleza Verde were used. Sowing was established in Petri dishes at the National Technological Institute of Mexico, Roque campus in November 2018. Three sowing densities, 3, 6 and 9 kg ha-1, were used. All variables were subjected to an analysis of variance and a comparison of means, with the SAS 9.0 package. The sowing density affected the root development of alfalfa, in particular the development of lateral roots and the presence of root hairs, but not the root length. The sowing density with the highest root development was with 9 kg ha-1. The exudates of alfalfa presented a very marked antagonistic effect on Arabidopsis thaliana by reducing its growth, this effect was higher for the density of 9 kg ha-1. A concentration of 50% or more of alfalfa exudates slows the growth until death of this Arabidopsis thaliana.

International audience | Abstract Arabidopsis thaliana is a suitable host for phytoparasitic nematodes of the genus Meloidogyne . Successful nematode infection leads to the formation of root galls. We tested for natural genetic variation and inoculation density effects on nematode reproductive success in the interaction between A. thaliana and Meloidogyne javanica . We inoculated different Arabidopsis genotypes with two sources of nematodes at two different doses, using a mild protocol for inoculum preparation. We counted root galls and egg masses 2 months after inoculation. We obtained a high number of successful nematode infections. Infection success differed among Arabidopsis genotypes in interaction with the nematode source. Overall, infection success and reproductive success of nematodes were lower at a higher inoculum dose of nematodes. Our results indicate that natural genetic variation in both host plants and nematodes, as well as short‐ and long‐term negative density effects, shape nematode reproductive success.

Der Beitrag stellt aktuelle Forschungsergebnisse der Abteilung ›Botanische Genetik und Molekularbiologie‹ der Christian-Albrechts-Universität zu Kiel vor, die bei der Untersuchung molekularer Prozesse innerhalb der pflanzlichen Mitochondrien des Modellorganismus Arabidopsis thaliana gewonnen wurden. Sie legen nahe, dass Ribosomen in den Mitochondrien eine variable Zusammensetzung haben und die Genexpression unter verschiedenen Bedingungen steuern. | This article presents recent research results from the Department of ›Botanical Genetics and Molecular Biology‹ at Kiel University, which were obtained by studying molecular processes within the plant mitochondria of the model organism Arabidopsis thaliana. They suggest that ribosomes in mitochondria have variable composition and control gene expression under different conditions.