Current challenges for plant biology research in the Global South.

In an attempt to address the large inequities faced by the plant biology communities from the Global South (i.e. countries located around the tropics and the Southern Hemisphere) at international conferences, this Viewpoint is the reflexive thinking arising from the concurrent session titled 'Arabidopsis and its translational research in the Global South' organized at the International Conference of Arabidopsis Research 2023 (ICAR 2023) in Chiba, Japan in June 2023.

Pleiotropic effects of melanin pigmentation: haemoparasite infection intensity but not telomere length is associated with plumage morph in black sparrowhawks.

There is increasing recognition of the potential pleiotropic effects of melanin pigmentation, particularly on immunity, with reports of variation in haemoparasite infection intensity and immune responses between the morphs of colour-polymorphic bird species. In a population of the black sparrowhawk () in western South Africa, light morphs have a higher haemoparasite infection intensity, but no physiological effects of this are apparent. Here, we investigate the possible effects of haemoparasite infection on telomere length in this species and explore whether relative telomere length is associated with either plumage morph or sex.

Novel roles for Arabidopsis dynamin-related proteins DRP1A and DRP2B in resistance against fungal infection.

Arabidopsis DYNAMIN-RELATED PROTEIN1A (DRP1A) and DRP2B are large GTPases that function together in endocytosis for effective cytokinesis, cell enlargement and development. A recent study shows that these DRPs contribute to ligand-induced endocytosis of the immune receptor FLAGELLIN SENSING2 (FLS2) to modulate flg22-immune signaling, and they are required for immunity against pv. bacteria.

Salt-Specific Gene Expression Reveals Elevated Auxin Levels in Plants Grown Under Saline Conditions.

Soil salinization is increasing globally, driving a reduction in crop yields that threatens food security. Salinity stress reduces plant growth by exerting two stresses on plants: rapid shoot ion-independent effects which are largely osmotic and delayed ionic effects that are specific to salinity stress. In this study we set out to delineate the osmotic from the ionic effects of salinity stress.

Conserved Opposite Functions in Plant Resistance to Biotrophic and Necrotrophic Pathogens of the Immune Regulator SRFR1.

Plant immunity is mediated in large part by specific interactions between a host resistance protein and a pathogen effector protein, named effector-triggered immunity (ETI). ETI needs to be tightly controlled both positively and negatively to enable normal plant growth because constitutively activated defense responses are detrimental to the host. In previous work, we reported that mutations in (), identified in a suppressor screen, reactivated EDS1-dependent ETI to pv.

Vegetative desiccation tolerance in the resurrection plant Xerophyta humilis has not evolved through reactivation of the seed canonical LAFL regulatory network.

It has been hypothesised that vegetative desiccation tolerance in resurrection plants evolved via reactivation of the canonical LAFL (i.e. LEC1, ABI3, FUS3 and LEC2) transcription factor (TF) network that activates the expression of genes during the maturation of orthodox seeds leading to desiccation tolerance of the plant embryo in most angiosperms.

Towards an Understanding of the Molecular Basis of Nickel Hyperaccumulation in Plants.

Metal hyperaccumulation is a rare and fascinating phenomenon, whereby plants actively accumulate high concentrations of metal ions in their above-ground tissues. Enhanced uptake and root-to-shoot translocation of specific metal ions coupled with an increased capacity for detoxification and sequestration of these ions are thought to constitute the physiological basis of the hyperaccumulation phenotype. Nickel hyperaccumulators were the first to be discovered and are the most numerous, accounting for some seventy-five percent of all known hyperaccumulators.

Comparative RNA-seq analysis of nickel hyperaccumulating and non-accumulating populations of Senecio coronatus (Asteraceae).

Most metal hyperaccumulating plants accumulate nickel, yet the molecular basis of Ni hyperaccumulation is not well understood. We chose Senecio coronatus to investigate this phenomenon as this species displays marked variation in shoot Ni content across ultramafic outcrops in the Barberton Greenstone Belt (South Africa), thus allowing an intraspecific comparative approach to be employed. No correlation between soil and shoot Ni contents was observed, suggesting that this variation has a genetic rather than environmental basis.

PceRBase: a database of plant competing endogenous RNA.

Competition for microRNA (miRNA) binding between RNA molecules has emerged as a novel mechanism for the regulation of eukaryotic gene expression. Competing endogenous RNA (ceRNA) can act as decoys for miRNA binding, thereby forming a ceRNA network by regulating the abundance of other RNA transcripts which share the same or similar microRNA response elements. Although this type of RNA cross talk was first described in Arabidopsis, and was subsequently shown to be active in animal models, there is no database collecting potential ceRNA data for plants.

Jasmonate signalling drives time-of-day differences in susceptibility of Arabidopsis to the fungal pathogen Botrytis cinerea.

The circadian clock, an internal time-keeping mechanism, allows plants to anticipate regular changes in the environment, such as light and dark, and biotic challenges such as pathogens and herbivores. Here, we demonstrate that the plant circadian clock influences susceptibility to the necrotrophic fungal pathogen, Botrytis cinerea. Arabidopsis plants show differential susceptibility to B.

Increased resistance to biotrophic pathogens in the Arabidopsis constitutive induced resistance 1 mutant is EDS1 and PAD4-dependent and modulated by environmental temperature.

The Arabidopsis constitutive induced resistance 1 (cir1) mutant displays salicylic acid (SA)-dependent constitutive expression of defence genes and enhanced resistance to biotrophic pathogens. To further characterise the role of CIR1 in plant immunity we conducted epistasis analyses with two key components of the SA-signalling branch of the defence network, ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) and PHYTOALEXIN DEFICIENT4 (PAD4). We demonstrate that the constitutive defence phenotypes of cir1 require both EDS1 and PAD4, indicating that CIR1 lies upstream of the EDS1-PAD4 regulatory node in the immune signalling network.

Circadian regulation of plant immunity to pathogens.

The plant circadian clock primes the immune response of Arabidopsis thaliana to infection with the bacterial pathogen Pseudomonas syringae pv tomato DC3000 (Pst DC3000) such that there is a more robust response during the subjective day than subjective night. Thus Pst DC3000 growth in plants infected with the same initial titre of bacteria varies depending on the time of day of infection (Bhardwaj et al., PLoS One 6: e26968, 2011; Zhang et al.

The window of desiccation tolerance shown by early-stage germinating seedlings remains open in the resurrection plant, Xerophyta viscosa.

Resurrection plants are renowned for their vegetative desiccation tolerance (DT). While DT in vegetative tissues is rare in angiosperms, it is ubiquitous in mature orthodox seeds. During germination, seedlings gradually lose DT until they pass a point of no return, after which they can no longer survive dehydration.

ERF5 and ERF6 play redundant roles as positive regulators of JA/Et-mediated defense against Botrytis cinerea in Arabidopsis.

The ethylene response factor (ERF) family in Arabidopsis thaliana comprises 122 members in 12 groups, yet the biological functions of the majority remain unknown. Of the group IX ERFs, the IXc subgroup has been studied the most, and includes ERF1, ERF14 and ORA59, which play roles in plant innate immunity. Here we investigate the biological functions of two members of the less studied IXb subgroup: ERF5 and ERF6.

Histidine biosynthesis.

Histidine (His) is one of the standard amino acids in proteins, and plays a critical role in plant growth and development. The chemical properties of the imidazole side group allow His to participate in acid-base catalysis, and in the co-ordination of metal ions. Despite the biological importance of this molecule, His biosynthesis has been somewhat neglected in plants, in stark contrast to micro-organisms where the study of this pathway was fundamental in the discovery of operon structure and regulation by attenuation.

The missing link in plant histidine biosynthesis: Arabidopsis myoinositol monophosphatase-like2 encodes a functional histidinol-phosphate phosphatase.

Histidine (His) plays a critical role in plant growth and development, both as one of the standard amino acids in proteins, and as a metal-binding ligand. While genes encoding seven of the eight enzymes in the pathway of His biosynthesis have been characterized from a number of plant species, the identity of the enzyme catalyzing the dephosphorylation of histidinol-phosphate to histidinol has remained elusive. Recently, members of a novel family of histidinol-phosphate phosphatase proteins, displaying significant sequence similarity to known myoinositol monophosphatases (IMPs) have been identified from several Actinobacteria.

OXI1 protein kinase is required for plant immunity against Pseudomonas syringae in Arabidopsis.

Expression of the Arabidopsis Oxidative Signal-Inducible1 (OXI1) serine/threonine protein kinase gene (At3g25250) is induced by oxidative stress. The kinase is required for root hair development and basal defence against the oomycete pathogen Hyaloperonospora parasitica, two separate H(2)O(2)-mediated processes. In this study, the role of OXI1 during pathogenesis was characterized further.

Relative contributions of nine genes in the pathway of histidine biosynthesis to the control of free histidine concentrations in Arabidopsis thaliana.

Despite the functional importance of histidine (His) as an essential amino acid in proteins and as a metal-coordinating ligand, comparatively little is known about the regulation of its biosynthesis in plants and the potential for metabolic engineering of this pathway. To investigate the contribution of different steps in the pathway to overall control of His biosynthesis, nine His biosynthetic genes were individually over-expressed in Arabidopsis thaliana to determine their effects on free amino acid pools. Constitutive, CaMV 35S-driven over-expression of the cDNAs encoding either isoform of ATP-phosphoribosyltransferase (ATP-PRT), the first enzyme in the pathway, was sufficient to increase the pool of free His by up to 42-fold in shoot tissue of Arabidopsis, with negligible effect on any other amino acid.

Chloroplast biogenesis during rehydration of the resurrection plant Xerophyta humilis: parallels to the etioplast-chloroplast transition.

De-etiolation of dark-grown seedlings is a commonly used experimental system to study the mechanisms of chloroplast biogenesis, including the stacking of thylakoid membranes into grana, the response of the nuclear-chloroplast transcriptome to light, and the ordered synthesis and assembly of photosystem II (PSII). Here, we present the xeroplast to chloroplast transition during rehydration of the resurrection plant Xerophyta humilis as a novel system for studying chloroplast biogenesis, and investigate the role of light in this process. Xeroplasts are characterized by the presence of numerous large and small membrane-bound vesicles and the complete absence of thylakoid membranes.

Basal resistance against Pseudomonas syringae in Arabidopsis involves WRKY53 and a protein with homology to a nematode resistance protein.

Basal resistance is the ultimately unsuccessful plant defense response to infection with a virulent pathogen. It is thought to be triggered by host recognition of pathogen-associated molecular patterns, with subsequent suppression of particular components by pathogen effectors. To identify novel components of Arabidopsis basal resistance against the bacterial pathogen Pseudomonas syringae pv.

Proteomic analysis of leaf proteins during dehydration of the resurrection plant Xerophyta viscosa.

The desiccation-tolerant phenotype of angiosperm resurrection plants is thought to rely on the induction of protective mechanisms that maintain cellular integrity during water loss. Two-dimensional (2D) sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the Xerophyta viscosa Baker proteome was carried out during dehydration to identify proteins that may play a role in such mechanisms. Quantitative analysis revealed a greater number of changes in protein expression levels at 35% than at 65% relative water content (RWC) compared to fully hydrated plants, and 17 dehydration-responsive proteins were identified by tandem mass spectrometry (MS).

PAMP recognition and the plant-pathogen arms race.

Plants have evolved systems analogous to animal innate immunity that recognise pathogen-associated molecular patterns (PAMPs). PAMP detection is an important component of non-host resistance in plants and serves as an early warning system for the presence of potential pathogens. Binding of a PAMP to the appropriate pattern recognition receptor leads to downstream signalling events and, ultimately, to the induction of basal defence systems.