Here, we report the complete genome sequence of the cytokinin-producing plant growth-promoting strain Pseudomonas fluorescens G20-18. The complete genome assembly resulted in a single, circular ...chromosome of 6.48 Mbp and harbors several secondary metabolite biosynthesis gene clusters that are potentially involved in its plant growth-promoting function.
PSK-α is a disulfated peptide that acts as a growth factor in plants. PSK-α is derived from preproproteins which are encoded by five PSK precursor genes in Arabidopsis thaliana (L.) Heynh and is ...perceived by leucine-rich repeat receptor kinases. Arabidopsis has two PSK receptor genes, PSKR1 and PSKR2. Although ligand and receptor are well characterized, the biological functions of PSK signaling are not well understood. Using reporter lines and receptor knockout mutants of Arabidopsis, a role for PSK signaling in biotic interactions and in wounding was analyzed. Treatment of Arabidopsis leaves with the fungal elicitor E-Fol, or the fungal pathogens Alternaria brassicicola and Sclerotinia sclerotiorum resulted in induction of PSK2 and PSKR1 as shown by promoter:GUS analysis. Wounding of hypocotyls or leaves induced PSK3:GUS, PSK5:GUS and PSKR1:GUS expression indicating that PSK precursor genes are differentially regulated in response to specific stresses. The receptor knockout lines pskr1-3 and pskr2-1 showed significantly reduced photosynthesis in response to the fungal elicitor E-Fol which indicates that fungal defence is impaired. pskr1-3 plants further showed reduced growth of crown galls after infection with Agrobacterium tumefaciens. A role for PSK signaling in Agrobacterium tumefaciens tumor growth was supported by the finding that PSK precursor genes and PSKR1 are expressed in crown galls. Overall, the results indicate that PSK signaling may play a previously undescribed role in pathogen or herbivore interactions and is crucial for Agrobacterium-induced cell proliferation in crown gall formation.
Summary
Extracellular or cell wall invertase is regarded as crucial to supply sink tissues with carbohydrates via an apoplastic pathway. A cell wall invertase from Chenopodium rubrum was purified to ...homogeneity and the corresponding cDNA encoding CIN1 was identified via peptide sequences. The CIN1 mRNA was found to be highly induced by physiological concentrations of both adenine‐ and phenylurea‐derived cytokinins in suspension culture cells. This was paralleled both by a higher steady‐state protein level and a higher enzyme activity of the extracellular invertase. The cytokinin‐inducible accumulation of CIN1 mRNA in tissues of C. rubrum plants supports the physiological significance of this regulatory mechanism. In contrast to the extracellular sucrose cleaving enzyme, the mRNA levels of the two putative intracellular invertases CIN2 and CIN3 and of sucrose synthase were not elevated. In addition, it has been found that the accumulation of mRNA for one out of three hexose transporters present in the suspension culture cells is induced co‐ordinately with the mRNA for extracellular invertase by cytokinins. It has been shown that this regulatory mechanism results in higher uptake rates both for sucrose, via the hexose monomers, and for glucose. The increased level of both extracellular invertase and hexose transporters and the resulting higher carbohydrate supply are discussed with respect to the control of carbohydrate partitioning by plant hormones and the molecular basis for known physiological cytokinin responses such as the stimulation of cell division.
Understanding temporal biological phenomena is a challenging task that can be approached using network analysis. Here, we explored whether network reconstruction can be used to better understand the ...temporal dynamics of bois noir, which is associated with '
Phytoplasma solani', and is one of the most widespread phytoplasma diseases of grapevine in Europe. We proposed a methodology that explores the temporal network dynamics at the community level, i.e., densely connected subnetworks. The methodology offers both insights into the functional dynamics via enrichment analysis at the community level, and analyses of the community dissipation, as a measure that accounts for community degradation. We validated this methodology with cases on experimental temporal expression data of uninfected grapevines and grapevines infected with '
. P. solani'. These data confirm some known gene communities involved in this infection. They also reveal several new gene communities and their potential regulatory networks that have not been linked to '
. P. solani' to date. To confirm the capabilities of the proposed method, selected predictions were empirically evaluated.
The regulation of carbon partitioning between source and sink tissues in higher plants is not only important for plant growth and development, but insight into the underlying regulatory mechanism is ...also a prerequisite to modulating assimilate partitioning in transgenic plants. Hexoses, as well as sucrose, have been recognised as important signal molecules in source-sink regulation. Components of the underlying signal transduction pathways have been identified and parallels, as well as distinct differences, to known pathways in yeast and animals have become apparent. There is accumulating evidence for crosstalk, modulation and integration between signalling pathways responding to phytohormones, phosphate, light, sugars, and biotic and abiotic stress-related stimuli. These complex interactions at the signal transduction levels and coordinated regulation of gene expression seem to play a central role in source-sink regulation.
Plant growth and consequently crop yield can be severely compromised by abiotic and biotic stress conditions. Transgenic approaches that resulted in increased tolerance against abiotic stresses often ...were typically accompanied by adverse effects on plant growth and fitness under optimal growing conditions. Proteins that belong to the PLAT-plant-stress protein family harbour a single PLAT (
P
olycystin,
L
ipoxygenase,
A
lpha-toxin and
T
riacylglycerol lipase) domain and are ubiquitously present in monocot and dicot plant species. Until now, only limited data is available for PLAT-plant-stress family members, which suggested that these proteins in general could promote tolerance towards stress responses. We studied the function of the
Arabidopsis
PLAT-plant-stress protein
At
PLAT1 employing heterologous gain-of-function analysis in tobacco.
At
PLAT1 conferred increased abiotic stress tolerance in tobacco, evident by improved tolerance towards cold, drought and salt stresses, and promoted growth, reflected by a faster development under non-stressed conditions. However, the overexpression of
AtPLAT1
in tobacco reduced the tolerance towards biotic stress conditions and, therefore, could be involved in regulating the crosstalk between abiotic and biotic stress responses. Thus, we showed that heterologously expressed
AtPLAT1
functions as positive regulator of abiotic stress tolerance and plant growth, which could be an important new asset for strategies to develop plants with improved abiotic stress tolerance, without growth and subsequent yield penalties under optimal growth conditions.
With increasing pollution, herbicide application and interest in plant phenotyping, sensors capturing early responses to toxic stress are demanded for screening susceptible or resistant plant ...varieties. Standard toxicity tests on plants are laborious, demanding in terms of space and material, and the measurement of growth-inhibition based endpoints takes relatively long time. The aim of this work was to explore the potential of photoautotrophic cell suspension cultures for high-throughput early toxicity screening based on imaging techniques. The investigation of the universal potential of fluorescence imaging methods involved testing of three toxicants with different modes of action (DCMU, glyphosate and chromium).
The increased pace of testing was achieved by using non-destructive imaging methods-multicolor fluorescence (MCF) and chlorophyll fluorescence (ChlF). These methods detected the negative effects of the toxicants earlier than it was reflected in plant growth inhibition (decrease in leaf area and final dry weight). Moreover, more subtle and transient effects not resulting in growth inhibition could be detected by fluorescence. The pace and sensitivity of stress detection was further enhanced by using photoautotrophic cell suspension cultures. These reacted sooner, more pronouncedly and to lower concentrations of the tested toxicants than the plants. Toxicant-specific stress signatures were observed as a combination of MCF and ChlF parameters and timing of the response. Principal component analysis was found to be useful for reduction of the collected multidimensional data sets to a few informative parameters allowing comparison of the toxicant signatures.
Photoautotrophic cell suspension cultures have proved to be useful for rapid high-throughput screening of toxic stress and display a potential for employment as an alternative to tests on whole plants. The MCF and ChlF methods are capable of distinguishing early stress signatures of at least three different modes of action.
To gain insight into the regulatory mechanisms of sugar signaling in plants, the effect of derivatives of the transport sugar sucrose (Suc), the Suc isomers palatinose and turanose, and the Suc ...analog fluoro-Suc were tested. Photo-autotrophic suspension culture cells of tomato (Lycopersicon peruvianum) were used to study their effect on the regulation of marker genes of source and sink metabolism, photosynthesis, and the activation of mitogen-activated protein kinases (MAPKs). Suc and glucose (Glc) resulted in reverse regulation of source and sink metabolism. Whereas the mRNA level of extracellular invertase (Lin6) was induced, the transcript level of small subunit of ribulose bisphosphate carboxylase (RbcS) was repressed. In contrast, turanose, palatinose, and fluoro-Suc only rapidly induced Lin6 mRNA level, whereas the transcript level of RbcS was not affected. The differential effect of the metabolizable and non-metabolizable sugars on RbcS mRNA regulation was reflected by the fact that only Suc and Glc inhibited photosynthesis and chlorophyll fluorescence. The activation of different signal transduction pathways by sugars was further supported by the analysis of the activation of MAPKs. MAPK activity was found to be strongly activated by turanose, palatinose, and fluoro-Suc, but not by Suc and Glc. To analyze the role of sugars in relation to pathogen perception, an elicitor preparation of Fusarium oxysporum lycopersici was used. The strong activation of MAPKs and the fast and transient induction of Lin6 expression by the fungal elicitor resembles the effect of turanose, palatinose, and fluoro-Suc and indicates that non-metabolizable sugars are sensed as stress-related stimuli.
•Strategies for future high throughput, non-destructive and cost-efficient measurement of plant traits are highlighted.•Use of low-cost and DIY approaches in phenomics provides opportunities for ...rapid prototyping and sensor development.•Robust protocols, data harmonization and provenance are critical to allow data reuse and cross validation of phenotypes.•Below-ground phenotyping is a major bottleneck and new technologies allowing the measurement of root-related traits are needed.
At the 4th International Plant Phenotyping Symposium meeting of the International Plant Phenotyping Network (IPPN) in 2016 at CIMMYT in Mexico, a workshop was convened to consider ways forward with sensors for phenotyping. The increasing number of field applications provides new challenges and requires specialised solutions. There are many traits vital to plant growth and development that demand phenotyping approaches that are still at early stages of development or elude current capabilities. Further, there is growing interest in low-cost sensor solutions, and mobile platforms that can be transported to the experiments, rather than the experiment coming to the platform. Various types of sensors are required to address diverse needs with respect to targets, precision and ease of operation and readout. Converting data into knowledge, and ensuring that those data (and the appropriate metadata) are stored in such a way that they will be sensible and available to others now and for future analysis is also vital. Here we are proposing mechanisms for “next generation phenomics” based on our learning in the past decade, current practice and discussions at the IPPN Symposium, to encourage further thinking and collaboration by plant scientists, physicists and engineering experts.
Dear Editor,
Plant cell suspension cultures have been used as model systems to circumvent the problems associated with the analyses of a multi-factorial plant that is composed of multiple tissue and ...cell types exposed to diverse signals. A number of plant suspension cultures have proven to be valuable to study various topics including defense response, secondary metabolite formation, ion transport, gene regulation, and signal duction （Roitsch and Sinha, 2002 and references therein）. However, most cultures reported to date, including the cultures from model species such as Arabidopsis （Christie and Jenkins,
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