Mobility of Transgenic Nucleic Acids and Proteins within Grafted Rootstocks for Agricultural Improvement.

Grafting has been used in agriculture for over 2000 years. Disease resistance and environmental tolerance are highly beneficial traits that can be provided through use of grafting, although the mechanisms, in particular for resistance, have frequently been unknown. As information emerges that describes plant disease resistance mechanisms, the proteins, and nucleic acids that play a critical role in disease management can be expressed in genetically engineered (GE) plant lines.

Identification and application of a rice senescence-associated promoter.

SAG39 is a rice (Oryza sativa) gene that encodes a cysteine protease. SAG39 shares 55% homology with the Arabidopsis (Arabidopsis thaliana) senescence-associated protein SAG12. The promoter for SAG39 (P(SAG39)) was isolated, and SAG39 expression was determined to be relatively low in mature leaves, while not expressed in the endosperm.

K+ transport in plants: physiology and molecular biology.

Potassium (K(+)) is an essential nutrient and the most abundant cation in plant cells. Plants have a wide variety of transport systems for K(+) acquisition, catalyzing K(+) uptake across a wide spectrum of external concentrations, and mediating K(+) movement within the plant as well as its efflux into the environment. K(+) transport responds to variations in external K(+) supply, to the presence of other ions in the root environment, and to a range of plant stresses, via Ca(2+) signaling cascades and regulatory proteins.

NH4+-stimulated and -inhibited components of K+ transport in rice (Oryza sativa L.).

The disruption of K(+) transport and accumulation is symptomatic of NH(4)(+) toxicity in plants. In this study, the influence of K(+) supply (0.02-40 mM) and nitrogen source (10 mM NH(4)(+) or NO(3)(-)) on root plasma membrane K(+) fluxes and cytosolic K(+) pools, plant growth, and whole-plant K(+) distribution in the NH(4)(+)-tolerant plant species rice (Oryza sativa L.

Non-reciprocal interactions between K+ and Na+ ions in barley (Hordeum vulgare L.).

The interaction of sodium and potassium ions in the context of the primary entry of Na(+) into plant cells, and the subsequent development of sodium toxicity, has been the subject of much recent attention. In the present study, the technique of compartmental analysis with the radiotracers (42)K(+) and (24)Na(+) was applied in intact seedlings of barley (Hordeum vulgare L.) to test the hypothesis that elevated levels of K(+) in the growth medium will reduce both rapid, futile Na(+) cycling at the plasma membrane, and Na(+) build-up in the cytosol of root cells, under saline conditions (100 mM NaCl).

Alleviation of rapid, futile ammonium cycling at the plasma membrane by potassium reveals K+-sensitive and -insensitive components of NH4+ transport.

Futile plasma membrane cycling of ammonium (NH4+) is characteristic of low-affinity NH4+ transport, and has been proposed to be a critical factor in NH4+ toxicity. Using unidirectional flux analysis with the positron-emitting tracer 13N in intact seedlings of barley (Hordeum vulgare L.), it is shown that rapid, futile NH4+ cycling is alleviated by elevated K+ supply, and that low-affinity NH4+ transport is mediated by a K+-sensitive component, and by a second component that is independent of K+.

The cytosolic Na+ : K+ ratio does not explain salinity-induced growth impairment in barley: a dual-tracer study using 42K+ and 24Na+.

It has long been believed that maintenance of low Na+ : K+ ratios in the cytosol of plant cells is critical to the plant's ability to tolerate salinity stress. Direct measurements of such ratios, however, have been few. Here we apply the non-invasive technique of compartmental analysis, using the short-lived radiotracers 42K+ and 22Na+, in intact seedlings of barley (Hordeum vulgare L.

The face value of ion fluxes: the challenge of determining influx in the low-affinity transport range.

The existence of distinct high- and low-affinity transport systems (HATS and LATS) is well established for major nutrient ions. However, influx mediated by these systems is usually estimated using uniformly simple tracer protocols. Two (42)K radiotracer methods to measure potassium influxes in the HATS and LATS ranges in intact barley (Hordeum vulgare L.

Rapid, futile K+ cycling and pool-size dynamics define low-affinity potassium transport in barley.

Using the short-lived radiotracer 42K+, we present a comprehensive subcellular flux analysis of low-affinity K+ transport in plants. We overturn the paradigm of cytosolic K+ pool-size homeostasis and demonstrate that low-affinity K+ transport is characterized by futile cycling of K+ at the plasma membrane. Using two methods of compartmental analysis in intact seedlings of barley (Hordeum vulgare L.

A new, non-perturbing, sampling procedure in tracer exchange measurements.

An isotope procedure for the tracing of ion fluxes and rate constants in intact plants is presented and applied to 42K-labelled potassium fluxes in cells of intact barley (Hordeum vulgare L.) roots. This procedure differs from conventional tracer efflux protocols in that tracer accrual in the external solution bathing the labelled roots is continually monitored by solution subsampling, whereas conventional protocols involve monitoring the specific-activity decline in a sequence of eluates that wash out tracer released by roots.

Cytosolic potassium homeostasis revisited: 42K-tracer analysis in Hordeum vulgare L. reveals set-point variations in [K+].

Current models of potassium acquisition and cytochemical processes in plants assume that potassium concentrations in the cytosol ([K+]cyt) are maintained homeostatically at approximately 100 mM. Here, we use 42K radiotracer data in the model plant species Hordeum vulgare L. (barley) to show that this assumption is incorrect.