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To gain more insight into the physiological function of nitrogen dioxide ( NO2), we investigated the effects of exogenous NO2 on growth in Arabidopsis thaliana., Plants were grown in air without NO2 for 1 wk after sowing and then grown for 1-4 wk in air with (designated treated plants) or without (control plants) NO2. Plants were irrigated semiweekly with a nutrient solution containing 19.7 mM nitrate and 10.3 mM ammonium., Five-week-old plants treated with 50 ppb NO2 showed a ≤ 2.8-fold increase in biomass relative to controls. Treated plants also showed early flowering. The magnitude of the effects of NO2 on leaf expansion, cell proliferation and enlargement was greater in developing than in maturing leaves. Leaf areas were 1.3-8.4 times larger on treated plants than corresponding leaves on control plants. The NO2-induced increase in leaf size was largely attributable to cell proliferation in developing leaves, but was attributable to both cell proliferation and enlargement in maturing leaves. The expression of different sets of genes for cell proliferation and/or enlargement was induced by NO2, but depended on the leaf developmental stage., Collectively, these results indicated that NO2 regulates organ growth by controlling cell proliferation and enlargement. [ABSTRACT FROM AUTHOR]

Particle bombardment has proved to be useful for the transformation of plants. We have previously reported successful transient expression of the β-glucuronidase (GUS) gene in cultured plant cells and tissues and the stable transformation of various plants using a pneumatic particle gun. In this chapter, we describe transient expression of the GUS gene in Arabidopsis thaliana leaves and roots using the pneumatic particle gun. [ABSTRACT FROM AUTHOR]

A plasmid pARK 22 harbouring the bar gene encoding phosphinothricin acetyltransferase (PAT) under the control of the cauliflower mosaic virus (CaMV) 35S promoter and nopaline synthase (NOS) terminator was constructed and introduced into root sections of Arabidopsis thaliana using the pneumatic particle gun. The root sections that had been bombarded with this plasmid gave four to eight times higher yield of drug-resistant calluses than those sections bombarded with pCaMVNEO or pCH, which respectively contain the neomycin phosphotransferase and hygromycin phosphotransferase genes. Among a number of primary transformant (T) plants obtained from independent bialaphos-resistant calluses, three were studied by Southern blot hybridization and PAT enzyme activity analyses, confirming the stable integration of the foreign gene into the Arabidopsis genome and its expression in plants. The progeny analysis showed transmission of the foreign gene and its expression in up to the T generation. Some of the T progeny showed morphological abnormalities. Thus, the bar gene can be used effectively to allow selection of transgenic A. thalianna plants. [ABSTRACT FROM AUTHOR]

Levels of NO-3, NO-2 and NH+4 ions in leaves of six plant species were determined by capillary electrophoresis. Levels of NO-3 ions differed by a factor of more than 350 in the six species. NO-2 and NH+4 ions were detected in all species examined but at lower and more similar respective levels than NO-3 ions. [ABSTRACT FROM AUTHOR]

Exposing Arabidopsis thaliana (Arabidopsis) seedlings fed with soil nitrogen to 10–50 ppb nitrogen dioxide (NO2) for several weeks stimulated the uptake of major elements, photosynthesis, and cellular metabolisms to more than double the biomass of shoot, total leaf area and contents of N, C P, K, S, Ca and Mg per shoot relative to non-exposed control seedlings. The 15N/14N ratio analysis by mass spectrometry revealed that N derived from NO2 (NO2-N) comprised < 5% of the total plant N, showing that the contribution of NO2-N as N source was minor. Moreover, histological analysis showed that leaf size and biomass were increased upon NO2 treatment, and that these increases were attributable to leaf age-dependent enhancement of cell proliferation and enlargement. Thus, NO2 may act as a plant growth signal rather than an N source. Exposure of Arabidopsis leaves to 40 ppm NO2 induced virtually exclusive nitration of PsbO and PsbP proteins (a high concentration of NO2 was used). The PMF analysis identified the ninth tyrosine residue of PsbO1 (9Tyr) as a nitration site. 9Tyr of PsbO1 was exclusively nitrated after incubation of the thylakoid membranes with a buffer containing NO2 and NO2− or a buffer containing NO2− alone. Nitration was catalyzed by illumination and repressed by photosystem II (PSII) electron transport inhibitors, and decreased oxygen evolution. Thus, protein tyrosine nitration altered (downregulated) the physiological function of cellular proteins of Arabidopsis leaves. This indicates that NO2-induced protein tyrosine nitration may stimulate plant growth. We hypothesized that atmospheric NO2 at ambient concentrations may induce tyrosine nitration of PYR/PYL/RCAR receptors in Arabidopsis leaves, followed by degradation of PYR/PYL/RCAR, upregulation of target of rapamycin (TOR) regulatory complexes, and stimulation of plant growth. [ABSTRACT FROM AUTHOR]