The Role of Ethylene in Plant Responses to K+ Deficiency

Potassium is an essential macronutrient that is involved in regulating turgor , in driving plant growth, and in modulating enzyme activation. The changes in root morphology, root function, as well as cellular and molecular responses to low potassium conditions have been studied in the model plant Arabidopsis and in other plant species. In Arabidopsis ethylene plays a key role in roots in the transduction of the low potassium signal, which results in altered root function and growth. The first clues regarding the role of ethylene were detected through transcriptional profiling experiments showing changes in the expression of genes related to ethylene biosynthesis. Later it was shown that ethylene plays a foundational early role in the many responses observed in Arabidopsis. One of the most striking findings is the link between ethylene and reactive oxygen species (ROS) production, which is part of the signal transduction pathway in K+ deprived plants. This mini-review will summarize what is known about the role ethylene plays in response to low potassium in Arabidopsis and other plant species

The Role of Ethylene in Plant Responses to K+ Deficiency

Potassium is an essential macronutrient that is involved in regulating turgor , in driving plant growth, and in modulating enzyme activation. The changes in root morphology, root function, as well as cellular and molecular responses to low potassium conditions have been studied in the model plant Arabidopsis and in other plant species. In Arabidopsis ethylene plays a key role in roots in the transduction of the low potassium signal, which results in altered root function and growth. The first clues regarding the role of ethylene were detected through transcriptional profiling experiments showing changes in the expression of genes related to ethylene biosynthesis. Later it was shown that ethylene plays a foundational early role in the many responses observed in Arabidopsis. One of the most striking findings is the link between ethylene and reactive oxygen species (ROS) production, which is part of the signal transduction pathway in K+ deprived plants. This mini-review will summarize what is known about the role ethylene plays in response to low potassium in Arabidopsis and other plant species

The Role of Ethylene in Plant Responses to K+ Deficiency

Potassium is an essential macronutrient that is involved in regulating turgor , in driving plant growth, and in modulating enzyme activation. The changes in root morphology, root function, as well as cellular and molecular responses to low potassium conditions have been studied in the model plant Arabidopsis and in other plant species. In Arabidopsis ethylene plays a key role in roots in the transduction of the low potassium signal, which results in altered root function and growth. The first clues regarding the role of ethylene were detected through transcriptional profiling experiments showing changes in the expression of genes related to ethylene biosynthesis. Later it was shown that ethylene plays a foundational early role in the many responses observed in Arabidopsis. One of the most striking findings is the link between ethylene and reactive oxygen species (ROS) production, which is part of the signal transduction pathway in K+ deprived plants. This mini-review will summarize what is known about the role ethylene plays in response to low potassium in Arabidopsis and other plant species

Root exudates impact plant performance under abiotic stress

Plant root exudates serve pivotal roles in supporting plant development and interactions with the physicochemical and biological factors in the rhizosphere. Under stress conditions, root exudation is involved in enhancing plant resource-use efficiency and facilitating the crosstalk between plant and soil microbes to ameliorate stress. Although there are a large number of root exudates that remain to be characterized, recent technological advancements have allowed for the function of many exudate compounds to be elucidated. In this review, we discuss current knowledge about the key root exudates that modulate plant resource-use efficiency under various abiotic stresses including drought, aluminum toxicity, phosphorus, nitrogen, and iron deficiency. The role that key root exudates play in shaping microbial communities in the rhizosphere under stress conditions is also an important consideration addressed in this review

Assessment of Bacterial Inoculant Delivery Methods for Cereal Crops

Despite growing evidence that plant growth-promoting bacteria can be used to improve crop vigor, a comparison of the different methods of delivery to determine which is optimal has not been published. An optimal inoculation method ensures that the inoculant colonizes the host plant so that its potential for plant growth-promotion is fully evaluated. The objective of this study was to compare the efficacy of three seed coating methods, seedling priming, and soil drench for delivering three bacterial inoculants to the sorghum rhizosphere and root endosphere. The methods were compared across multiple time points under axenic conditions and colonization efficiency was determined by quantitative polymerase chain reaction (qPCR). Two seed coating methods were also assessed in the field to test the reproducibility of the greenhouse results under non-sterile conditions. In the greenhouse seed coating methods were more successful in delivering the Gram-positive inoculant (Terrabacter sp.) while better colonization from the Gram-negative bacteria (Chitinophaga pinensis and Caulobacter rhizosphaerae) was observed with seedling priming and soil drench. This suggested that Gram-positive bacteria may be more suitable for the seed coating methods possibly because of their thick peptidoglycan cell wall. We also demonstrated that prolonged seed coating for 12 h could effectively enhance the colonization of C. pinensis, an endophytic bacterium, but not the rhizosphere colonizing C. rhizosphaerae. In the field only a small amount of inoculant was detected in the rhizosphere. This comparison demonstrates the importance of using the appropriate inoculation method for testing different types of bacteria for their plant growth-promotion potential

Elucidating Sorghum Biomass, Nitrogen and Chlorophyll Contents With Spectral and Morphological Traits Derived From Unmanned Aircraft System

Unmanned aircraft systems (UAS) provide an efficient way to phenotype cropmorphology with spectral traits such as plant height, canopy cover and various vegetation indices (VIs) providing information to elucidate genotypic responses to the environment. In this study, we investigated the potential use of UAS-derived traits to elucidate biomass, nitrogen and chlorophyll content in sorghum under nitrogen stress treatments. A nitrogen stress trial located in Nebraska, USA, contained 24 different sorghum lines, 2 nitrogen treatments and 8 replications, for a total of 384 plots. Morphological and spectral traits including plant height, canopy cover and various VIs were derived from UAS flights with a true-color RGB camera and a 5-band multispectral camera at early, mid and late growth stages across the sorghum growing season in 2017. Simple and multiple regression models were investigated for sorghum biomass, nitrogen and chlorophyll content estimations using the derived morphological and spectral traits along with manual ground truthed measurements. Results showed that, the UAS-derived plant height was strongly correlated with manually measured plant height (r = 0.85); and the UAS-derived biomass using plant height, canopy cover and VIs had strong exponential correlations with the sampled biomass of fresh stalks and leaves (maximum r = 0.85) and the biomass of dry stalks and leaves (maximum r = 0.88). The UAS-derived VIs were moderately correlated with the laboratory measured leaf nitrogen content (r = 0.52) and the measured leaf chlorophyll content (r = 0.69) in each plot. The methods developed in this study will facilitate genetic improvement and agronomic studies that require assessment of stress responses in large-scale field trials

The Amino Acid Permeases AAP3 and AAP6 Are Involved in Root-Knot Nematode Parasitism of \u3cem\u3eArabidopsis\u3c/em\u3e

The root-knot nematode, Meloidogyne incognita, is an obligate parasite which depends entirely on the host plant for its nutrition. Root-knot nematodes induce the formation of a highly specialized feeding site consisting of several giant cells surrounded by a network of vascular tissues. Nutrients, including amino acids and sugars, are transferred apoplastically from the vascular tissues to the feeding site. Using Arabidopsis thaliana lacking the vascular-expressed amino acid permeases (AAP) AAP3 or AAP6, we demonstrate that disruption of amino acid transport can affect nematode parasitism. Nematode infestation levels are significantly reduced on the aap3 and aap6 mutants. AAP3 and AAP6 act distinctly in the transport of amino acids to the feeding site, as demonstrated by differences in their carrying capacity profiles. Furthermore, analyses of promoter: β-glucuronidase lines show different expression patterns for AAP3 and AAP6 in infected roots. In the aap3-3 mutant, part of the decrease in infestation is connected to a defect in early infection, where juveniles enter but then leave the root. Both aap3-3 and aap6-1 produce fewer females and produce more adult male nematodes. Additionally, detrimental effects are observed in the nematodes harvested from aap3-3 and aap6-1 mutants, including decreased egg hatching and infectivity and lower levels of lipid reserves. The transport of amino acids by AAP3 and AAP6 is important for nematode infection and success of the progeny

Tomato root transcriptome response to a nitrogen-enriched soil patch

Background: Nitrogen (N), the primary limiting factor for plant growth and yield in agriculture, has a patchy distribution in soils due to fertilizer application or decomposing organic matter. Studies in solution culture oversimplify the complex soil environment where microbial competition and spatial and temporal heterogeneity challenge roots\u27 ability to acquire adequate amounts of nutrients required for plant growth. In this study, various ammonium treatments (as 15N) were applied to a discrete volume of soil containing tomato (Solanum lycopersicum) roots to simulate encounters with a localized enriched patch of soil. Transcriptome analysis was used to identify genes differentially expressed in roots 53 hrs after treatment. Results: The ammonium treatments resulted in significantly higher concentrations of both ammonium and nitrate in the patch soil. The plant roots and shoots exhibited increased levels of 15N over time, indicating a sustained response to the enriched environment. Root transcriptome analysis identified 585 genes differentially regulated 53 hrs after the treatments. Nitrogen metabolism and cell growth genes were induced by the high ammonium (65 μg NH4 +-N g-1 soil), while stress response genes were repressed. The complex regulation of specific transporters following the ammonium pulse reflects a simultaneous and synergistic response to rapidly changing concentrations of both forms of inorganic N in the soil patch. Transcriptional analysis of the phosphate transporters demonstrates cross-talk between N and phosphate uptake pathways and suggests that roots increase phosphate uptake via the arbuscular mycorrhizal symbiosis in response to N. Conclusion: This work enhances our understanding of root function by providing a snapshot of the response of the tomato root transcriptome to a pulse of ammonium in a complex soil environment. This response includes an important role for the mycorrhizal symbiosis in the utilization of an N patch. Additional files attached below

Evaluation of UAV-derived multimodal remote sensing data for biomass prediction and drought tolerance assessment in bioenergy sorghum

Screening for drought tolerance is critical to ensure high biomass production of bioenergy sorghum in arid or semi-arid environments. The bottleneck in drought tolerance selection is the challenge of accurately predicting biomass for a large number of genotypes. Although biomass prediction by low-altitude remote sensing has been widely investigated on various crops, the performance of the predictions are not consistent, especially when applied in a breeding context with hundreds of genotypes. In some cases, biomass prediction of a large group of genotypes benefited from multimodal remote sensing data; while in other cases, the benefits were not obvious. In this study, we evaluated the performance of single and multimodal data (thermal, RGB, and multispectral) derived from an unmanned aerial vehicle (UAV) for biomass prediction for drought tolerance assessments within a context of bioenergy sorghum breeding. The biomass of 360 sorghum genotypes grown under well-watered and water-stressed regimes was predicted with a series of UAV-derived canopy features, including canopy structure, spectral reflectance, and thermal radiation features. Biomass predictions using canopy features derived from the multimodal data showed comparable performance with the best results obtained with the single modal data with coefficients of determination (R2) ranging from 0.40 to 0.53 under water-stressed environment and 0.11 to 0.35 under well-watered environment. The significance in biomass prediction was highest with multispectral followed by RGB and lowest with the thermal sensor. Finally, two well-recognized yield-based drought tolerance indices were calculated from ground truth biomass data and UAV predicted biomass, respectively. Results showed that the geometric mean productivity index outperformed the yield stability index in terms of the potential for reliable predictions by the remotely sensed data. Collectively, this study demonstrated a promising strategy for the use of different UAV-based imaging sensors to quantify yield-based drought tolerance