Swarming Behavior in Plant Roots

Interactions between individuals that are guided by simple rules can generate swarming behavior. Swarming behavior has been observed in many groups of organisms, including humans, and recent research has revealed that plants also demonstrate social behavior based on mutual interaction with other individuals. However, this behavior has not previously been analyzed in the context of swarming. Here, we show that roots can be influenced by their neighbors to induce a tendency to align the directions of their growth. In the apparently noisy patterns formed by growing roots, episodic alignments are observed as the roots grow close to each other. These events are incompatible with the statistics of purely random growth. We present experimental results and a theoretical model that describes the growth of maize roots in terms of swarming

Root-emitted volatile organic compounds: can they mediate belowground plant-plant interactions?

peer reviewedBackground Aboveground, plants release volatile organic compounds (VOCs) that act as chemical signals between neighbouring plants. It is now well documented that VOCs emitted by the roots in the plant rhizosphere also play important ecological roles in the soil ecosystem, notably in plant defence because they are involved in interactions between plants, phytophagous pests and organisms of the third trophic level. The roles played by root-emitted VOCs in between- and within-plant signalling, however, are still poorly documented in the scientific literature. Scope Given that (1) plants release volatile cues mediating plant-plant interactions aboveground, (2) roots can detect the chemical signals originating from their neighbours, and (3) roots release VOCs involved in biotic interactions belowground, the aim of this paper is to discuss the roles of VOCs in between- and within-plant signalling belowground. We also highlight the technical challenges associated with the analysis of root-emitted VOCs and the design of experiments targeting volatile-mediated root-root interactions. Conclusions We conclude that root-root interactions mediated by volatile cues deserve more research attention and that both the analytical tools and methods developed to study the ecological roles played by VOCs in interplant signalling aboveground can be adapted to focus on the roles played by root-emitted VOCs in between- and within-plant signalling

Transcriptome analysis of Arabidopsis thaliana plants in response to kin and stranger recognition

Recent reports have demonstrated that Arabidopsis thaliana has the ability to alter its growth differentially when grown in the presence of secretions from other A. thaliana plants that are kin or strangers; however, little knowledge has been gained as to the physiological processes involved in these plant-plant interactions. Therefore, we examined the root transcriptome of A. thaliana plants exposed to stranger vs. kin secretions to determine genes involved in these processes. We conducted a whole transcriptome analysis on root tissues and categorized genes with significant changes in expression. Genes from four categories of interest based on significant changes in expression were identified as ATP/GST transporter, auxin/auxin related, secondary metabolite and pathogen response genes. Multiple genes in each category were tested and results indicated that pathogen response genes were involved in the kin recognition response. Plants were then infected with Pseudomonas syringe pv. Tomato DC3000 to further examine the role of these genes in plants exposed to own, kin and stranger secretions in pathogen resistance. This study concluded that multiple physiological pathways are involved in the kin recognition. The possible implication of this study opens up a new dialog in terms of how plant-plant interactions change under a biotic stress

The role of ABC transporters in kin recognition in Arabidopsis thaliana

The ability to sense and respond to the surrounding rhizosphere including communications with neighboring plants and microbes is essential for plant survival. Recently, it has been established that several plant species including Arabidopsis thaliana have the ability to recognize rhizospheric neighbors based or their genetic identity. This study investigated the role of ABC transporters in kin recognition in A. thaliana based on previous evidence that root secretions are involved in the kin recognition response and that ABC transporters are responsible for secretion of a number of compounds. Three genes, AtPGP1, AtATH1 and AtATH10, are all implicated to be partially involved in the complex kin recognition response in A. thaliana based on this report. These findings highlight the importance of ABC transporters in understanding root secretions and plant-plant community interactions

Timed Sequential Treatment With Cyclophosphamide, Doxorubicin, and an Allogeneic Granulocyte-Macrophage Colony-Stimulating Factor–Secreting Breast Tumor Vaccine: A Chemotherapy Dose-Ranging Factorial Study of Safety and Immune Activation

PurposeGranulocyte-macrophage colony-stimulating factor (GM-CSF) -secreting tumor vaccines have demonstrated bioactivity but may be limited by disease burdens and immune tolerance. We tested the hypothesis that cyclophosphamide (CY) and doxorubicin (DOX) can enhance vaccine-induced immunity in patients with breast cancer.Patients and methodsWe conducted a 3 x 3 factorial (response surface) dose-ranging study of CY, DOX, and an HER2-positive, allogeneic, GM-CSF-secreting tumor vaccine in 28 patients with metastatic breast cancer. Patients received three monthly immunizations, with a boost 6 to 8 months from study entry. Primary objectives included safety and determination of the chemotherapy doses that maximize HER2-specific immunity.ResultsTwenty-eight patients received at least one immunization, and 16 patients received four immunizations. No dose-limiting toxicities were observed. HER2-specific delayed-type hypersensitivity developed in most patients who received vaccine alone or with 200 mg/m(2) CY. HER2-specific antibody responses were enhanced by 200 mg/m(2) CY and 35 mg/m(2) DOX, but higher CY doses suppressed immunity. Analyses revealed that CY at 200 mg/m(2) and DOX at 35 mg/m(2) is the combination that produced the highest antibody responses.ConclusionFirst, immunotherapy with an allogeneic, HER2-positive, GM-CSF-secreting breast tumor vaccine alone or with CY and DOX is safe and induces HER2-specific immunity in patients with metastatic breast cancer. Second, the immunomodulatory activity of low-dose CY has a narrow therapeutic window, with an optimal dose not exceeding 200 mg/m(2). Third, factorial designs provide an opportunity to identify the most active combination of interacting drugs in patients. Further investigation of the impact of chemotherapy on vaccine-induced immunity is warranted