Hormonal and metabolic responses of Mexican lime plants to CTV infection.

Plant viral infections alter gene expression and metabolism in infected host. To study the molecular responses of Mexican lime to CTV infection, an analysis of plant metabolome in response to infection with severe (T318) or mild (T385) isolates of CTV was performed. Healthy plants and those infected with any of the two virus strains showed different metabolite profiles, at different stages of new sprout development. Proline content increased in plants infected with CTV, proportionally to the virulence of the virus strain. Abscisic acid content decreased after virus infection whereas jasmonic and salicylic acid levels increased. CTV infection had an impact on plant secondary metabolism, by stimulating the synthesis of different metabolites such as l-methylhistidine, phenylpropanoid derivatives. These metabolites are common responses of different organisms, including higher mammals, to viral diseases, and its presence in this system points to the existence of universal responses to virus infection among different kingdoms.

Shotgun proteomic analysis of the Mexican lime tree infected with "CandidatusPhytoplasma aurantifolia".

Infection of Mexican lime trees (Citrus aurantifolia L.) with the specialized bacterium "CandidatusPhytoplasma aurantifolia" causes witches' broom disease. Witches' broom disease has the potential to cause significant economic losses throughout western Asia and North Africa. We used label-free quantitative shotgun proteomics to study changes in the proteome of Mexican lime trees in response to infection by "Ca. Phytoplasma aurantifolia". Of 990 proteins present in five replicates of healthy and infected plants, the abundances of 448 proteins changed significantly in response to phytoplasma infection. Of these, 274 proteins were less abundant in infected plants than in healthy plants, and 174 proteins were more abundant in infected plants than in healthy plants. These 448 proteins were involved in stress response, metabolism, growth and development, signal transduction, photosynthesis, cell cycle, and cell wall organization. Our results suggest that proteomic changes in response to infection by phytoplasmas might support phytoplasma nutrition by promoting alterations in the host's sugar metabolism, cell wall biosynthesis, and expression of defense-related proteins. Regulation of defense-related pathways suggests that defense compounds are induced in interactions with susceptible as well as resistant hosts, with the main differences between the two interactions being the speed and intensity of the response.

Nitric oxide: a common antipathogenic factor of plants.

In the present study, nitric oxide synthase/nitric oxide (NOS/NO) status was tested in the host plants infected with fungi, bacteria and virus. In each case cytosolic nitric oxide synthase (Cyt-NOS) of diseased plants was inhibited and inhibition was competitive in nature in respect to l-arginine, the substrate for the enzymic activity. Elevation of host nitric oxide (NO) level before infection using nitric oxide (NO) donor protected disease initiation significantly. The nature of enzyme kinetics and the manner of disease protection by nitric oxide donor (NO-donor) was similar in all the three cases of infection. It was concluded that nitric oxide was a common antipathogenic factor of plants.

Modulation of digoxin transport across Caco-2 cell monolayers by citrus fruit juices: lime, lemon, grapefruit, and pummelo.

PURPOSE: To evaluate the effects of fresh lime, lemon, grapefruit, and pummelo juices on the transport of digoxin, a P-glycoprotein (P-gp) substrate, in Caco-2 cell monolayers. METHODS: Bidirectional [3H]-digoxin fluxes across confluent Caco-2 cell monolayers were determined in 0-50% fruit juices at pH 7.4. Verapamil HCl (100 microM) served as positive control. Juice toxicity was evaluated by the 3-(4,5 dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay. RESULTS: Apical-to-basal (A-to-B) digoxin flux was enhanced by 50% fruit juice in the order of lemon > lime > pummelo > grapefruit. The four fruit juices could be divided into two groups based on their effects on transepithelial electrical resistance (TEER), viability, and digoxin transport activity of the Caco-2 cells. Grapefruit and pummelo juices produced similar digoxin transport profiles that were characteristic of those observed with P-gp inhibitors. Both juices decreased net digoxin efflux by 1.2 U per 10% increase in juice concentration and had a propensity to increase cellular TEER at high concentrations (>30%). However, cellular TEER and viability decreased with increasing concentration of lime and lemon juices. Both juices also produced similar digoxin transport profiles, the A-to-B and B-to-A digoxin Papp increasing with increasing juice concentration above 5%. Net digoxin efflux was 30% of control value and relatively independent of juice concentration. These results paralleled the groupings of the four fruits according to their prominent flavonoid pattern and taxonomy. CONCLUSION: The effects of lime, lemon, grapefruit, and pummelo juices on the TEER, viability, and digoxin transport activity of the Caco-2 cells appeared to be dependent on the dominant flavonoid pattern and taxonomy of the citrus fruits.