Modification of Leaf Apoplastic pH in Relation to Stomatal Sensitivity to Root-Sourced Abscisic Acid Signals

Jia, Wensuo; Davies, W. J.

doi:10.1104/pp.106.089110

Cited by 158 publications

(124 citation statements)

References 19 publications

(25 reference statements)

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“…2). At lower pHs, such as those of the tomato leaf apoplast (pH 5.0 to 6.0 [29]), citrate is an effective iron carrier and could be a preferred DC3000 siderophore (Table 1). In addition, apoplastic leaf iron is mostly in the form of ironcitrate chelates (9,38,39).…”

Section: Pvdmentioning

confidence: 99%

The Phytopathogen Pseudomonas syringae pv. tomato DC3000 Has Three High-Affinity Iron-Scavenging Systems Functional under Iron Limitation Conditions but Dispensable for Pathogenesis

Jones

Wildermuth

2011

J Bacteriol

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High-affinity iron scavenging through the use of siderophores is a well-established virulence determinant in mammalian pathogenesis. However, few examples have been reported for plant pathogens. Here, we use a genetic approach to investigate the role of siderophores in Pseudomonas syringae pv. tomato DC3000 (DC3000) virulence in tomato. DC3000, an agronomically important pathogen, has two known siderophores for highaffinity iron scavenging, yersiniabactin and pyoverdin, and we uncover a third siderophore, citrate, required for growth when iron is limiting. Though growth of a DC3000 triple mutant unable to either synthesize or import these siderophores is severely restricted in iron-limited culture, it is fully pathogenic. One explanation for this phenotype is that the DC3000 triple mutant is able to directly pirate plant iron compounds such as heme/hemin or iron-nicotianamine, and our data indicate that DC3000 can import iron-nicotianamine with high affinity. However, an alternative explanation, supported by data from others, is that the pathogenic environment of DC3000 (i.e., leaf apoplast) is not iron limited but is iron replete, with available iron of >1 M. Growth of the triple mutant in culture is restored to wild-type levels by supplementation with a variety of iron chelates at >1 M, including iron(III) dicitrate, a dominant chelate of the leaf apoplast. This suggests that lower-affinity iron import would be sufficient for DC3000 iron nutrition in planta and is in sharp contrast to the high-affinity iron-scavenging mechanisms required in mammalian pathogenesis.Pathogenic microorganisms must acquire all critical nutrients from the host environment in order to survive. Iron nutrition in particular presents a fundamental challenge due to its extremely low solubility in aerobic environments at moderate pHs (ϳ10 Ϫ9 M) and further host limitation of available free iron (e.g., ϳ10Ϫ18 M in mammalian fluids [22,44]). Most bacteria require much higher levels (i.e., 10 Ϫ6 to 10 Ϫ7 M of bioavailable iron) for optimal growth (24) and therefore must solve an iron supply problem for survival. There is abundant evidence that competition for iron is a key virulence determinant in mammalian pathosystems. Iron in human serum is predominantly complexed with transferrin protein (pFe ϭ 10 22 M [1]) and is therefore limited from invading pathogens. The human immune system can limit iron further through release of the iron-binding protein lactoferrin at the site of infection (57). Evading these defenses, several mammalian pathogens pirate host-synthesized heme for iron nutrition directly from host fluids (20). Alternatively, pathogenic bacteria can scavenge iron from host fluids using very high-affinity iron carriers termed siderophores that can effectively compete with host iron chelates for iron. Siderophores are low-molecular-weight compounds that are synthesized, exported from the bacterial cell, and then imported once bound to iron (43). As this strategy carries metabolic costs associated with siderophore synthesis and transp...

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Section: Pvdmentioning

confidence: 99%

The Phytopathogen Pseudomonas syringae pv. tomato DC3000 Has Three High-Affinity Iron-Scavenging Systems Functional under Iron Limitation Conditions but Dispensable for Pathogenesis

Jones

Wildermuth

2011

J Bacteriol

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“…much less than the values that have been assumed, such as 0.3; Nobel, 2004). When nitrate is abundant in the xylem sap and/or the soil is dry, the pH of the apoplast water could increase up to neutral levels (Jia and Davies, 2007). Then, diffusion of HCO 3 -should be considered.…”

mentioning

confidence: 96%

Leaf Functional Anatomy in Relation to Photosynthesis

et al. 2010

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Rubisco is a large enzyme with a molecular mass of approximately 550 kD. The maximum rate of CO 2 fixation (i.e. ribulose-1,5-bisphosphate [RuBP] carboxylation) at CO 2 saturation is only 15 to 30 mol CO 2 mol 21 Rubisco protein s 21 at 25°C. Affinity to CO 2 is also low, and the K m , K c , at 25°C in the absence of oxygen is comparable to the CO 2 concentration in water equilibrated with air containing 39 Pa CO 2 (approximately 390 mL L 21 ), 13 mM. Moreover, RuBP carboxylation is competitively inhibited by RuBP oxygenation, which is the primary step of the energy-wasting process, photorespiration. If the CO 2 concentration in the chloroplast stroma is low, the carboxylation rate will decrease while the oxygenation rate will increase. Under such conditions, light energy and other resources, including nitrogen and water, are all wasted, eventually leading to a decrement of fitness of the plants. From these data, we may consider that structural features of the leaf contributing to the maintenance of the high CO 2 concentration in the chloroplast stroma may have been selected during evolution.In this Update, we focus on the key structural features that affect CO 2 concentration in the chloroplast stroma. First, we analyze the conductance for CO 2 diffusion from the substomatal cavity to the chloroplast stroma (mesophyll conductance [g m ], also called internal conductance). Because the low g m limits photosynthesis,

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“…It should be noted that the soil drying-induced xylem pH increase and the changes of xylem chemical composition or content may be two different concepts. This is because NO3 −, NH4 + and some other ions have actually no significant effect on xylem pH, but once transported to the leaf they may strongly modify the appolastic pH, and such a viewpoint has been proved by the recent study of Jia and Davies (2007). In regards to pH signaling in response to soil drying, we should not only pay attention to whether soil drying may directly affect xylem pH, but also pay close attention to whether it may affect the chemical composition or content, and also whether a type of soil may directly affect the chemical composition or content.…”

Section: Modulation Of Ph Signaling 421 Effect Of Chemical Compositmentioning

confidence: 99%

“…It is hypothesized that high VPD may affect leaf cell H + -ATPase activity by causing slight changes in localised water relation, and high PPFD may increase the removal of CO2 from apopalst, thus causing an apoplastic alkalization (Hartung and Radin 1989;Wilkinson and Davies 2002). Jia and Davies (2007) found that a great pH gradient exists between the stem base xylem and the leaf vascular system in many plant species. Also, it was found that a change in transpiration rate would be able to cause a change in the leaf xylem sap or apoplastic pH.…”

Section: Effect Of H + -Exchange Between Xylem Vessel and The Surrounmentioning

confidence: 99%

“…M¨ uhling and Lauchli (2001) also found that nitrate nutrition caused more alkaline leaf apoplastic sap than ammonium nutrition, in both Phaseolus vulgaris and sunflower, but not in Vicia faba or Zea mays. More recently, using a pH ratio imaging technique, Jia and Davies (2007) clearly showed that feeding NO 3 − induced a significant alkalization of the leaf apoplast, while the feeding of NH 4 + had a contrary effect (i.e. it gave rise to a significant reduction of the apoplastic pH in Commelina communis).…”

Section: Coordination Of Aba and Ph Signalingmentioning

confidence: 99%

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Systemic Signaling Under Water Deficit Condition and Its Exploitation in Water Saving Agriculture

Li¹,

Jia²

2012

Water Stress

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Modification of Leaf Apoplastic pH in Relation to Stomatal Sensitivity to Root-Sourced Abscisic Acid Signals

Cited by 158 publications

References 19 publications

The Phytopathogen Pseudomonas syringae pv. tomato DC3000 Has Three High-Affinity Iron-Scavenging Systems Functional under Iron Limitation Conditions but Dispensable for Pathogenesis

The Phytopathogen Pseudomonas syringae pv. tomato DC3000 Has Three High-Affinity Iron-Scavenging Systems Functional under Iron Limitation Conditions but Dispensable for Pathogenesis

Leaf Functional Anatomy in Relation to Photosynthesis

Systemic Signaling Under Water Deficit Condition and Its Exploitation in Water Saving Agriculture

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