Bacterial volatiles (mVOC) emitted by the phytopathogen Erwinia amylovora promote Arabidopsis thaliana growth and oxidative stress

Phytopathogens are well known for their devastating activity that causes worldwide significant crop losses. However, their exploitation for crop welfare is relatively unknown. Here, we show that the microbial volatile organic compound (mVOC) profile of the bacterial phytopathogen, Erwinia amylovora, enhances Arabidopsis thaliana shoot and root growth. GC-MS head-space analyses revealed the presence of typical microbial volatiles, including 1-nonanol and 1-dodecanol. E. amylovora mVOCs triggered early signaling events including plasma transmembrane potential Vm depolarization, cytosolic Ca2+ fluctuation, K+ -gated channel activity, and reactive oxygen species (ROS) and nitric oxide (NO) burst from few minutes to 16 h upon exposure. These early events were followed by the modulation of the expression of genes involved in plant growth and defense responses and responsive to phytohormones, including abscisic acid, gibberellin, and auxin (including the efflux carriers PIN1 and PIN3). When tested, synthetic 1-nonanol and 1-dodecanol induced root growth and modulated genes coding for ROS. Our results show that E. amylovora mVOCs affect A. thaliana growth through a cascade of early and late signaling events that involve phytohormones and RO

Three-component condencations of 3-amino-1,2,4-triazoles, methyl 3-(2-cycloamino-4-methylpyrimidin-5-yl)-3- oxopropionoates, and a series of c1 synthons as a convenient approach to pyrimidin-5-yl-1,2,4-triazolo[1,5-a] pyrimidines

A convenient synthetic approach to polysubstituted dihydrogenated or heteroaromatic 1,2,4-triazolo- [1,5-a] pyrimidines derivatives containing at position 5 a 4-methylpyrimidine moiety bearing a cycloamino substituent at position 2 and linked to the triazolopyrimidine bicycle through its position 5 was developed. The approach involves unusual three-component condensations of 3-amino-1,2,4-triazoles, methyl 3-(2-R-4-methylpyrimidin- 5-yl)-3-oxopropionates, and a series of C1 synthons whose synthetic equivalents are a series of aromatic aldehydes, triethyl orthoformate, or DMFDMA were used as of C1 synthon

The AUXIN BINDING PROTEIN 1 Is Required for Differential Auxin Responses Mediating Root Growth

Background In plants, the phytohormone auxin is a crucial regulator sustaining growth and development. At the cellular level, auxin is interpreted differentially in a tissue- and dose-dependent manner. Mechanisms of auxin signalling are partially unknown and the contribution of the AUXIN BINDING PROTEIN 1 (ABP1) as an auxin receptor is still a matter of debate. Methodology/Principal Findings Here we took advantage of the present knowledge of the root biological system to demonstrate that ABP1 is required for auxin response. The use of conditional ABP1 defective plants reveals that the protein is essential for maintenance of the root meristem and acts at least on the D-type CYCLIN/RETINOBLASTOMA pathway to control entry into the cell cycle. ABP1 affects PLETHORA gradients and confers auxin sensitivity to root cells thus defining the competence of the cells to be maintained within the meristem or to elongate. ABP1 is also implicated in the regulation of gene expression in response to auxin. Conclusions/Significance Our data support that ABP1 is a key regulator for root growth and is required for auxin-mediated responses. Differential effects of ABP1 on various auxin responses support a model in which ABP1 is the major regulator for auxin action on the cell cycle and regulates auxin-mediated gene expression and cell elongation in addition to the already well known TIR1-mediated ubiquitination pathway

Alanine Zipper-Like Coiled-Coil Domains Are Necessary for Homotypic Dimerization of Plant GAGA-Factors in the Nucleus and Nucleolus

GAGA-motif binding proteins control transcriptional activation or repression of homeotic genes. Interestingly, there are no sequence similarities between animal and plant proteins. Plant BBR/BPC-proteins can be classified into two distinct groups: Previous studies have elaborated on group I members only and so little is known about group II proteins. Here, we focused on the initial characterization of AtBPC6, a group II protein from Arabidopsis thaliana. Comparison of orthologous BBR/BPC sequences disclosed two conserved signatures besides the DNA binding domain. A first peptide signature is essential and sufficient to target AtBPC6-GFP to the nucleus and nucleolus. A second domain is predicted to form a zipper-like coiled-coil structure. This novel type of domain is similar to Leucine zippers, but contains invariant alanine residues with a heptad spacing of 7 amino acids. By yeast-2-hybrid and BiFC-assays we could show that this Alanine zipper domain is essential for homotypic dimerization of group II proteins in vivo. Interhelical salt bridges and charge-stabilized hydrogen bonds between acidic and basic residues of the two monomers are predicted to form an interaction domain, which does not follow the classical knobs-into-holes zipper model. FRET-FLIM analysis of GFP/RFP-hybrid fusion proteins validates the formation of parallel dimers in planta. Sequence comparison uncovered that this type of domain is not restricted to BBR/BPC proteins, but is found in all kingdoms

Grain jeld and kernel weight of two maize genotypes differing in nitrogen use efficiency at variuos levels of nitrogen and carbohydrate availability during flowering and grain filling

Grain yield per plant (GYP) and mean kernel weight (KW) of maize (Zea mays L.) are sensitive to changes in the environment during the lag phase of kernel growth (the time after pollination in which the potential kernel size is determined), and during the phase of linear kernel growth. The aim of this study was to assess genotypic differences in the response to environmental stresses associated with N and/or carbohydrate shortage at different phases during plant development. The rate and timing of N and carbo- hydrate supply were modified by application of fertilizer, shading, and varying the plant density at sow- ing, at silking or at 14 d after silking. The effects of these treatments on the photosynthetic capacity, grain yield and mean kernel weight were investigated in two hybrids differing in N use efficiency. The total above-ground biomass and grain yield per plant of the efficient hybrid responded little to altered environmental conditions such as suboptimal N supply, enhanced inter-plant competition, and shading for 14 d during flowering, when compared to the less efficient genotype. We conclude that grain yields in the efficient genotype are less sensitive not only to N stress, but also to carbohydrate shortage before grain filling. Shading of N deficient plants from 14 d after silking to maturity did not significantly reduce grain yield in the non-efficient genotype, indicating complete sink limitation of grain yield during grain filling. In the efficient genotype, in contrast, grain yield of N-deficient plants was significantly reduced by shading during grain filling. The rate of photosynthesis declined with decreasing foliar N content. No genotypic differences in photosynthesis were observed at high or low foliar N contents. However, at high plant density and low N supply, the leaf chlorophyll content after flowering in the efficient genotype was higher than that in the non-efficient genotype. Obviously, the higher source capacity of the efficient geno- type was not due to higher photosynthetic N use efficiency but due to maintenance of high chlorophyll contents under stressful conditions. In the efficient genotype, the harvest index was not significantly affected by N fertilization, plant density, or shading before the grain filling period. In contrast, in the non-efficient genotype the harvest index was diminished by N deficiency and shading during flowering. We conclude that the high yielding ability of the efficient genotype under stressful conditions was associated with formation of a high sink capacity of the grains under conditions of low carbohydrate and N availability during flowering and with maintenance of high source strength during grain filling under conditions of high plant density and low N availability

Kernel set in maize genotypes differing in nitrogen use efficiency in response to resource availability around flowering

Environmental conditions affect grain yield in maize (Zea mays L.) mainly by altering the kernel number per plant (KNP). This number is determined during a critical period of about 2 weeks around silking. The objectives of this study were to assess how the rate and timing of nitrogen (N) fertilizer applications affect biomass partitioning and KNP in two genotypes with different N use efficiency, and to compare kernel set of these genotypes under varying regimes of carbohydrate and N availability during the criti- cal period for kernel set. In the first field experiment, plant density and the rate of N supply per plant were varied independently. In the second field experiment, N availability was controlled via the applica- tion of N fertilizer, and carbohydrate availability was controlled by shading or thinning at silking. In both experiments, low rates of N supply reduced KNP more strongly in the non-efficient genotype when compared to the efficient genotype. The genotypic differences in kernel set were neither associated with N uptake into the above-ground biomass at maturity, nor above-ground biomass at silking. In the non- efficient genotype, application of N fertilizer at silking increased KNP. This increase was not associated with an increase in plant growth but with increased partitioning of biomass towards the reproductive organs during the critical period for kernel set. The genotype which had been selected for its high N use efficiency also showed higher kernel set at high plant density and shading during flowering when com- pared to the non-efficient genotype. Under conditions of restricted resource availability per plant, plant and ear growth rates during the critical period of about 14 days after onset of flowering declined com- pared with non-limiting conditions. However, these growth rates were less reduced in the efficient geno- type. Pooling treatments of different plant density and different available N, each hybrid showed linear responses of KNP to plant growth rate and to ear growth rate. Furthermore, in the efficient genotype KNP was reduced to a lesser extent in response to decreasing growth rates. We conclude that higher kernel set of the efficient genotype compared to the non-efficient genotype under stressful conditions was associated with low sensitivity of plant growth and dry matter distribution towards reproductive organs to low assimilate availability during the critical period of kernel set, and particularly with low sensitivity of kernel set to decreasing plant and ear growth rates