Single-stranded oligodeoxynucleotides induce plant defence in Arabidopsis thaliana.

Background And Aims: Single-stranded DNA oligodeoxynucleotides (ssODNs) have been shown to elicit immune responses in mammals. In plants, RNA and genomic DNA can activate immunity, although the exact mechanism through which they are sensed is not clear. The aim of this work was to study the possible effect of ssODNs on plant immunity.

The histone-like protein HupB influences biofilm formation and virulence in Xanthomonas citri ssp. citri through the regulation of flagellar biosynthesis.

Citrus canker is an important disease of citrus, whose causal agent is the bacterium Xanthomonas citri ssp. citri (Xcc). In previous studies, we found a group of Xcc mutants, generated by the insertion of the Tn5 transposon, which showed impaired ability to attach to an abiotic substrate.

POLAR-guided signalling complex assembly and localization drive asymmetric cell division.

Stomatal cell lineage is an archetypal example of asymmetric cell division (ACD), which is necessary for plant survival. In Arabidopsis thaliana, the GLYCOGEN SYNTHASE KINASE3 (GSK3)/SHAGGY-like kinase BRASSINOSTEROID INSENSITIVE 2 (BIN2) phosphorylates both the mitogen-activated protein kinase (MAPK) signalling module and its downstream target, the transcription factor SPEECHLESS (SPCH), to promote and restrict ACDs, respectively, in the same stomatal lineage cell. However, the mechanisms that balance these mutually exclusive activities remain unclear.

Coronatine Inhibits Stomatal Closure through Guard Cell-Specific Inhibition of NADPH Oxidase-Dependent ROS Production.

Microbes trigger stomatal closure through microbe-associated molecular patterns (MAMPs). The bacterial pathogen pv. () synthesizes the polyketide toxin coronatine, which inhibits stomatal closure by MAMPs and by the hormone abscisic acid (ABA).

Xanthomonas campestris attenuates virulence by sensing light through a bacteriophytochrome photoreceptor.

Phytochromes constitute a major photoreceptor family found in plants, algae, fungi, and prokaryotes, including pathogens. Here, we report that Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot disease which affects cruciferous crops worldwide, codes for a functional bacteriophytochrome (XccBphP).

Xanthan Pyruvilation Is Essential for the Virulence of Xanthomonas campestris pv. campestris.

Xanthan, the main exopolysaccharide (EPS) synthesized by Xanthomonas spp., contributes to bacterial stress tolerance and enhances attachment to plant surfaces by helping in biofilm formation. Therefore, xanthan is essential for successful colonization and growth in planta and has also been proposed to be involved in the promotion of pathogenesis by calcium ion chelation and, hence, in the suppression of the plant defense responses in which this cation acts as a signal.

Brassinosteroids tailor stomatal production to different environments.

Two recent reports show that brassinosteroids control stomata production by regulating the GSK3-like kinase BIN2-mediated phosphorylation of two different stomatal signalling components resulting in opposite stomatal phenotypes. We discuss how these two mechanisms might differentially control stomatal generation under diverse growth conditions.

SPEECHLESS integrates brassinosteroid and stomata signalling pathways.

Stomatal formation is regulated by multiple developmental and environmental signals, but how these signals are integrated to control this process is not fully understood. In Arabidopsis thaliana, the basic helix-loop-helix transcription factor SPEECHLESS (SPCH) regulates the entry, amplifying and spacing divisions that occur during stomatal lineage development. SPCH activity is negatively regulated by mitogen-activated protein kinase (MAPK)-mediated phosphorylation.

Plants grow on brassinosteroids.

Brassinosteroids (BRs) are plant steroid hormones known mainly for promoting organ growth through their combined effect on cell expansion and division. In addition, BRs regulate a broad spectrum of plant developmental and physiological responses, including plant architecture, vascular differentiation, male fertility, flowering, senescence, photomorphogenesis and tolerance to biotic and abiotic stresses. Recently, a complete core BR signaling pathway was defined in which BR signals are conveyed from the cell surface to the nucleus through sequential signaling modules.

Stomata and pathogens: Warfare at the gates.

Bacteria and fungi are capable of triggering stomatal closure through pathogen-associated molecular patterns (PAMPs), which prevents penetration through these pores. Therefore, the stomata can be considered part of the plant innate immune response. Some pathogens have evolved mechanisms to evade stomatal defense.

Expression of ABA signalling genes and ABI5 protein levels in imbibed Sorghum bicolor caryopses with contrasting dormancy and at different developmental stages.

Background And Aims: Pre-harvest sprouting susceptibility in grain sorghum (Sorghum bicolor) is related to low seed dormancy and reduced embryo sensitivity to inhibition of germination by abscisic acid (ABA). Intra-specific variability for pre-harvest sprouting might involve differential regulation of ABA signalling genes.

Methods: Sorghum genes encoding homologues for ABA signalling components from other species (ABI5, ABI4, VP1, ABI1 and PKABA1) were studied at the transcriptional and protein level (ABI5) during grain imbibition for two sorghum lines with contrasting sprouting phenotypes and in response to hormones.

Xanthomonas campestris overcomes Arabidopsis stomatal innate immunity through a DSF cell-to-cell signal-regulated virulence factor.

Pathogen-induced stomatal closure is part of the plant innate immune response. Phytopathogens using stomata as a way of entry into the leaf must avoid the stomatal response of the host. In this article, we describe a factor secreted by the bacterial phytopathogen Xanthomonas campestris pv campestris (Xcc) capable of interfering with stomatal closure induced by bacteria or abscisic acid (ABA).

Arabidopsis MPK3, a Key Signalling Intermediate in Stomatal Function.

Regulation of stomatal aperture is of critical importance to plants to balance gas exchange and water loss, and also to control ingress of bacterial pathogens. MAP kinase signal transduction pathways are mediators of biotic and abiotic stress, and have been indicted in the control of stomatal movements. Cell-specific antisense was used to down-regulate MPK3 gene expression in Arabidopsis guard cells, resulting in ABA insensitivity during inhibition of stomatal opening, but a normal ABA response in promotion of closure assays.

Guard cell-specific inhibition of Arabidopsis MPK3 expression causes abnormal stomatal responses to abscisic acid and hydrogen peroxide.

MAP kinases have been linked to guard cell signalling. Arabidopsis thaliana MAP Kinase 3 (MPK3) is known to be activated by abscisic acid (ABA) and hydrogen peroxide (H(2)O(2)), which also control stomatal movements. We therefore studied the possible role of MPK3 in guard cell signalling through guard cell-specific antisense inhibition of MPK3 expression.