The Pseudomonas fluorescens Siderophore Pyoverdine Weakens Arabidopsis thaliana Defense in Favor of Growth in Iron-Deficient Conditions

Abstract

Pyoverdines are siderophores synthesized by fluorescent Pseudomonas spp. Under iron-limiting conditions, these high-affinity ferric iron chelators are excreted by bacteria in the soil to acquire iron. Pyoverdines produced by beneficial Pseudomonas spp. ameliorate plant growth. Here, we investigate the physiological incidence and mode of action of pyoverdine from Pseudomonas fluorescens C7R12 on Arabidopsis (Arabidopsis thaliana) plants grown under iron-sufficient or iron-deficient conditions. Pyoverdine was provided to the medium in its iron-free structure (apo-pyoverdine), thus mimicking a situation in which it is produced by bacteria. Remarkably, apo-pyoverdine abolished the iron-deficiency phenotype and restored the growth of plants maintained in the iron-deprived medium. In contrast to a P. fluorescens C7R12 strain impaired in apo-pyoverdine production, the wild-type C7R12 reduced the accumulation of anthocyanins in plants grown in iron-deficient conditions. Under this condition, apo-pyoverdine modulated the expression of around 2,000 genes. Notably, apo-pyoverdine positively regulated the expression of genes related to development and iron acquisition/redistribution while it repressed the expression of defense-related genes. Accordingly, the growth-promoting effect of apo-pyoverdine in plants grown under iron-deficient conditions was impaired in iron-regulated transporter1 and ferric chelate reductase2 knockout mutants and was prioritized over immunity, as highlighted by an increased susceptibility to Botrytis cinerea. This process was accompanied by an overexpression of the transcription factor HBI1, a key node for the cross talk between growth and immunity. This study reveals an unprecedented mode of action of pyoverdine in Arabidopsis and demonstrates that its incidence on physiological traits depends on the plant iron status.

Changes in iron availability in Arabidopsis are rapidly sensed in the leaf vasculature and impaired sensing leads to opposite transcriptional programs in leaves and roots

“…HEMA1 encodes a Glu‐tRNA reductase involved in tetrapyrrole biosynthesis; HEMA1 is expressed in both mesophyll and companion cells (Mustroph et al, ) and is rapidly repressed during Fe deficiency (Rodríguez‐Celma et al, ). SAT1 (At1g55920) and GH9C1 (At1g48930) are two additional genes that are induced by Fe deficiency in leaves and are expressed in both mesophyll and companion cells (Mustroph et al, ; Trapet et al, ). The precise timing of induction however has not been determined but these genes, together with the mesophyll and companion cell markers identified in the present work, may help defining better Fe deficiency responses in leaves at cell‐specific resolution.…”

Application of Bio P60 and Bio T10 Alone or in Combination Against Stem Rot of Pakcoy

“…P. fluorescens has the ability to form siderophore but not all are toxic to plant pathogens (Luján et al, 2015;Trapet et al, 2016). This causes P. fluorescens to suppress the intensity of the disease.…”

Diversity, Phylogeny and Plant Growth Promotion Traits of Nodule Associated Bacteria Isolated from Lotus parviflorus

“…Moreover, isolates LpA6, LpB5b, LpB12a, and LpB16d, which showed siderophore production, are closely related to Pseudomonas spp. (Pseudomonas koreensis and Pseudomonas fluorescens) that are commonly reported to show this trait [77,[79][80][81]. Similarly, phosphate solubilization was shown by the pseudomonad isolate LpB16d that is related to P. koreensis, which has also been shown previously to solubilize phosphate [82][83][84].…”