Accumulation of nitrate in the shoot acts as a signal to regulate shoot‐root allocation in tobacco†

  title={Accumulation of nitrate in the shoot acts as a signal to regulate shoot‐root allocation in tobacco†},
  author={Wolf-R{\"u}diger Scheible and Marianne Lauerer and E. D. Schulze and Michel Caboche and Mark Stitt},
  journal={Plant Journal},
Mutants and transformants of tobacco (Nicotiania tabacum L. cv Gatersleben 1) with decreased expression of nitrate reductase have been used to investigate whether nitrate accumulation in the shoot acts as a signal to alter allocation between shoot and root growth. (a) Transformants with very low (1–3% of wild-type levels) nitrate reductase activity had growth rates, and protein, amino acid and glutamine levels similar to or slightly lower than a nitrate-limited wild-type, but accumulated large… 

Lateral root frequency decreases when nitrate accumulates in tobacco transformants with low nitrate reductase activity: consequences for the regulation of biomass partitioning between shoots and root1

It is concluded that nitrate accumulation in the plant leads to decreased root growth via (i) changes in carbon allocation leading to decreased allocation of sugars to root growth, and (ii) a decrease in the number of lateral roots and a shift in the sensitivity with which root growth responds to the sugar supply.

functional nitrate reductase in the roots

Unexpectedly, the C/N balance and the functional equilibrium between root and shoot growth was dis turbed dramatically by the loss of nitrate reduction in the root, and transformed plants showed an altered allocation of amino-N between the root and the shoot.

Nitrate acts as a signal to control gene expression, metabolism and biomass allocation

Tobacco genotypes with decreased activity of nitrate reductase [NR] have been used to establish an in plant screen for processes that are regulated by nitrate. These genotypes resemble

Elevated pCO(2 )favours nitrate reduction in the roots of wild-type tobacco (Nicotiana tabacum cv. Gat.) and significantly alters N-metabolism in transformants lacking functional nitrate reductase in the roots.

Unexpectedly, the C/N balance and the functional equilibrium between root and shoot growth was disturbed dramatically by the loss of nitrate reduction in the root, and transformed plants showed an altered allocation of amino-N between the root and the shoot.

Regulation of resource allocation during reproductive growth in Arabidopsis thaliana L. Heynh

Abi3-1 seeds may be seen as having reduced capacity for growth which causes stimulation of floral meristem development by feedback of sucrose in the phloem, and it is proposed that resource allocation is regulated by competition for resources between sinks maintaining sucrose concentration gradients in thephloem.

Plant response to nitrate starvation is determined by N storage capacity matched by nitrate uptake capacity in two Arabidopsis genotypes.

It was demonstrated that line 432 coped better with NO(3)(-)-starvation, producing higher shoot and root biomass and sustaining maximal growth for a longer time, suggesting that the corresponding nitrate transporters may be preferentially involved under fluctuating N supply conditions.

Expression of a deregulated tobacco nitrate reductase gene in potato increases biomass production and decreases nitrate concentration in all organs

It is concluded that enhancement of nitrate reduction rate leads to higher biomass production, probably by allowing a better allocation of N-resources to photosynthesis and C-metabolism.

The role of nitrate reduction in the anoxic metabolism of roots I. Characterization of root morphology and normoxic metabolism of wild type tobacco and a transformant lacking root nitrate reductase

WT versus LNR-H plants are a suitable tool to re-evaluate the role of nitrate reduction in flooding tolerance and show consistently higher respiration and higher contents of ATP, starch and hexose monophosphates than WT roots.

Genome-wide responses to shoot nitrate satiety are attenuated by external ammonium in Arabidopsis thaliana

It is shown that genome-wide transcriptional responses to shoot nitrate satiety are significantly lowered in the presence of external ammonium especially in the shoot.

Boron deficiency decreases plasmalemma H+-ATPase expression and nitrate uptake, and promotes ammonium assimilation into asparagine in tobacco roots

Results suggest that boron deficiency decreases net nitrate uptake by declining the activity of nitrate transporters rather than affecting their transcript levels, which suggest that this mineral deficiency may promote ammonium assimilation via asparagine synthetase in tobacco roots.



Higher plant responses to environmental nitrate

In this model, nitrate is a signal for developmental changes in the physiology of the plant, which are expressed in a hierarchy and the primary responses include induction of genes for nitrate and nitrite reductases,Nitrate uptake and translocation systems, and DNA regulatory proteins required for expression of the secondary response gene systems.

Growth and reproduction of Arabidopsis thaliana in relation to storage of starch and nitrate in the wild‐type and in starch‐deficient and nitrate‐uptake‐deficient mutants

It is demonstrated that resource assimilation during the reproductive phase determines seed production, and starch formation is not only an important factor during growth in the rosette phase, but is also important for whole plant allocation during seed formation.

Translocation of N to and from barley roots: its dependence on local nitrate supply in split‐root culture

Cycling of N to roots, and cycling of N in the plant as a whole, is substantial also during N-limited growth, as indicated by results indicate that increased external availability of N also increased the sink strength of the root for cycling N.

Low CO(2) Prevents Nitrate Reduction in Leaves.

There is a rapid inactivation/activation mechanism of NR in leaves which couples nitrate reductase to net photosynthesis which appears to be responsible for the inhibition of nitrate reduction in water stressed leaves.

Cytokinin concentration in relation to mineral nutrition and benzyladenine treatment in Plantago major ssp. pleiosperma

The glucosides were the only major cytokinins enhanced by mineral shortage and this effect of low mineral supply was retarded but not entirely prevented by exogenous BA.

Phloem‐specific expression of pyrophosphatase inhibits long distance transport of carbohydrates and amino acids in tobacco plants

A small decrease in the hexose phosphate/UDP-glucose ratio, the ATP/ADP ratio and the respiration rate in the midribs of the transformants provides evidence Hint mobilization of sucrose via pyrophosphate-dependent reactions is necessary for phloem energy metabolism.

Alteration in carbon partitioning induced by the movement protein of tobacco mosaic virus originates in the mesophyll and is independent of change in the plasmodesmal size exclusion limit

It is proposed that the TMV-MP interferes with an endogenous signal transduction pathway that involves macromolecular trafficking through plasmodesmata to regulate biomass partitioning between the source and various sink tissues.

Nitrate: nutrient and signal for plant growth.

This review provides an update on recent molecular advances that have uncovered genes and mechanisms responsible for nitrate uptake, reduction, and regulation and explains how this regulatory network is responsive to both interna1 and external signals.

Nitrate transport is independent of NADH and NAD(P)H nitrate reductases in barley seedlings.

Induction of nitrate transporters and the kinetics of net nitrates uptake were the same for all four genotypes indicating that neither nitrate reductase isozyme has a direct role in nitrate uptake in barley seedlings.

Relation between photosynthetic starch formation and dry-weight partitioning between the shoot and root.

The results suggested that carbon partitioned into leaf starch was preferentially utilized for growth of shoots at night, and was supported by diurnal dry-weight changes of various parts of 'Ransom' soybean plants.