Strigolactone analogs act as new anti-cancer agents in inhibition of breast cancer in xenograft model

Strigolactones (SLs) are a novel class of plant hormones. Previously, we found that analogs of SLs induce growth arrest and apoptosis in breast cancer cell lines. These compounds also inhibited the growth of breast cancer stem cell enriched-mammospheres with increased potency. Furthermore, strigolactone analogs inhibited growth and survival of colon, lung, prostate, melanoma, osteosarcoma and leukemia cancer cell lines. To further examine the anti-cancer activity of SLs in vivo, we have examined their effects on growth and viability of MDA-MB-231 tumor xenografts model either alone or in combination with paclitaxel. We show that strigolactone act as new anti-cancer agents in inhibition of breast cancer in xenograft model. In addition we show that SLs affect the integrity of the microtubule network and therefore may inhibit the migratory phenotype of the highly invasive breast cancer cell lines that were examined

Changes in the allocation of endogenous strigolactone improve plant biomass production on phosphate-poor soils.

Strigolactones (SLs) are carotenoid-derived phytohormones shaping plant architecture and inducing the symbiosis with endomycorrhizal fungi. In Petunia hybrida, SL transport within the plant and towards the rhizosphere is driven by the ABCG-class protein PDR1. PDR1 expression is regulated by phytohormones and by the soil phosphate abundance, and thus SL transport integrates plant development with nutrient conditions. We overexpressed PDR1 (PDR1 OE) to investigate whether increased endogenous SL transport is sufficient to improve plant nutrition and productivity. Phosphorus quantification and nondestructive X-ray computed tomography were applied. Morphological and gene expression changes were quantified at cellular and whole tissue levels via time-lapse microscopy and quantitative PCR. PDR1 OE significantly enhanced phosphate uptake and plant biomass production on phosphate-poor soils. PDR1 OE plants showed increased lateral root formation, extended root hair elongation, faster mycorrhization and reduced leaf senescence. PDR1 overexpression allowed considerable SL biosynthesis by releasing SL biosynthetic genes from an SL-dependent negative feedback. The increased endogenous SL transport/biosynthesis in PDR1 OE plants is a powerful tool to improve plant growth on phosphate-poor soils. We propose PDR1 as an as yet unexplored trait to be investigated for crop production. The overexpression of PDR1 is a valuable strategy to investigate SL functions and transport routes

A tomato strigolactone-impaired mutant displays aberrant shoot morphology and plant interactions

Strigolactones are considered a new group of plant hormones. Their role as modulators of plant growth and signalling molecules for plant interactions first became evident in Arabidopsis, pea, and rice mutants that were flawed in strigolactone production, release, or perception. The first evidence in tomato (Solanum lycopersicon) of strigolactone deficiency is presented here. Sl-ORT1, previously identified as resistant to the parasitic plant Orobanche, had lower levels of arbuscular mycorrhizal fungus (Glomus intraradices) colonization, possibly as a result of its reduced ability to induce mycorrhizal hyphal branching. Biochemical analysis of mutant root extracts suggested that it produces only minute amounts of two of the tomato strigolactones: solanacol and didehydro-orobanchol. Accordingly, the transcription level of a key enzyme (CCD7) putatively involved in strigolactone synthesis in tomato was reduced in Sl-ORT1 compared with the wild type (WT). Sl-ORT1 shoots exhibited increased lateral shoot branching, whereas exogenous application of the synthetic strigolactone GR24 to the mutant restored the WT phenotype by reducing the number of lateral branches. Reduced lateral shoot branching was also evident in grafted plants which included a WT interstock, which was grafted between the mutant rootstock and the scion. In roots of these grafted plants, the CCD7 transcription level was not significantly induced, nor was mycorrhizal sensitivity restored. Hence, WT-interstock grafting, which restores mutant shoot morphology to WT, does not restore mutant root properties to WT. Characterization of the first tomato strigolactone-deficient mutant supports the putative general role of strigolactones as messengers of suppression of lateral shoot branching in a diversity of plant species

Understanding Soil Respiration: an integrated approach

Soil respiration is a key factor for understanding the responses of terrestrial ecosystems to climate change, and it is crucial to understand the effects of variation in biophysical regulators of soil respiration for assessing carbon balance of forested temperate ecosystem. One fundamental challenge for soil research is the spatial and temporal heterogeneity of soil processes. Therefore, we deployed a dense array of soil sensor in combination with minirhizotrons to study variation in soil temperature, moisture, root production, and rhizomorph production on soil respiration within natural spatial gradients at the James Reserve. We used Structural Equation Modeling (SEM) to find out which factors are significant to the soil respiration in various depths

Understanding Soil Respiration: an integrated approach

Soil respiration is a key factor for understanding the responses of terrestrial ecosystems to climate change, and it is crucial to understand the effects of variation in biophysical regulators of soil respiration for assessing carbon balance of forested temperate ecosystem. One fundamental challenge for soil research is the spatial and temporal heterogeneity of soil processes. Therefore, we deployed a dense array of soil sensor in combination with minirhizotrons to study variation in soil temperature, moisture, root production, and rhizomorph production on soil respiration within natural spatial gradients at the James Reserve. We used Structural Equation Modeling (SEM) to find out which factors are significant to the soil respiration in various depths

Data from: Drought-adapted plants dramatically downregulate dinitrogen fixation: evidences from Mediterranean legume shrubs

1. The importance of symbiotic dinitrogen (N2) fixation in shaping the coupled nitrogen-carbon cycle is now known for most humid terrestrial ecosystems. However, whether N2 fixation can play a key role in the nitrogen and carbon budget of water-limited and seasonally dry ecosystems remains a mystery. 2. The maintenance of metabolically and physiologically costly symbiotic fixation in water-limited environments is highly complex. These costs are particularly high during the first developmental season, when allocation to deep rooting and drought-resistance mechanisms is essential for seedling survival of prolonged seasonal drought. 3. We therefore evaluated how drought-adapted legume species change their allocation to symbiotic nitrogen fixation as a function of soil nitrogen availability. We tested this on seedlings of a suite of four common Mediterranean legume shrubs with a strong seasonal behavior, which we grew under controlled nitrogen and phosphorus availabilities. We asked: (1) Do species differ in their investment and regulation of nitrogen fixation? (2) Is fixation regulated via plant allocation to nodules, fixation rate, or both? and (3) Does phosphorus availability limit symbiotic nitrogen fixation? 4. All Mediterranean perennial legumes in the experiment established and grew nodulated and fixed nitrogen, even under severe nitrogen limitation. The four species reacted similarly to nitrogen supply, by strongly downregulating fixation through both decreased nodulation and lower rate of fixation. However, we found a significant inter-specific difference in fixation (both nodulation and rate), biomass production and growth rate. Our experimental species presented a range of fixation investment strategies corresponding to life history and resource partitioning patterns. Phosphorus limitation had a minor influence on both fixation and plant growth. 5. Synthesis: the high physiological cost of symbiotic fixation imposes the need to tightly regulate fixation in perennial legumes coping with severe water stress and seasonal conditions. Control of fixation allows legume species to colonize recently disturbed nitrogen-deficient habitats, cope with grazing, survive long seasonal droughts and recover nitrogen fixation latter in the wet season, and survive over time by reducing nitrogen inputs to the ecosystem