Nitrate reductase (NR) is post-translationally regulated by phosphorylation and binding of 14-3-3 proteins. Deletion of 56 amino acids in the amino-terminal domain of NR was previously shown to impair this type of regulation in tobacco (Nicotiana plumbaginifolia) (L. Nussaume, M. Vincentez, C. Meyer, J.-P. Boutin, M. Caboche [1995] Plant Cell 7: 611-621), although both full-length NR and delete...

Requirements for intron recognition during pre-mRNA splicing in plants differ from those in vertebrates and yeast. Plant introns contain neither conserved branch points nor distinct 3' splice site-proximal polypyrimidine tracts characteristic of the yeast and vertebrate introns, respectively. However, they are strongly enriched in U residues throughout the intron, property essential for splicin...

HsfA2 is a heat stress (hs)-induced Hsf in peruvian tomato (Lycopersicon peruvianum) and the cultivated form Lycopersicon esculentum. Due to the high activator potential and the continued accumulation during repeated cycles of heat stress and recovery, HsfA2 becomes a dominant Hsf in thermotolerant cells. The formation of heterooligomeric complexes with HsfA1 leads to nuclear retention and enha...

Silencing of a Nicotiana plumbaginifolia beta-1,3-glucanase (gn1) transgene in tobacco line T17 occurs in homozygous and in haploid plants with one transgene locus dosage per chromosome set. We have previously shown that the silent state is manifested by a reduced gn1 steady state mRNA level and results from a post-transcriptional process that is under developmental control in homozygous T17 pl...

Diurnal variations in nitrate reductase (NR) activity and nitrogen metabolites were examined in wild-type Nicotiana plumbaginifolia and transformants with various degrees of NR deregulation. In the C1 line, NR was only deregulated at the transcriptional level by placing the NR gene under the control of the cauliflower mosaic virus 35S RNA promoter. In the Del8 and S521D lines, NR was additional...

Superoxide dismutases (SODs) are metalloproteins that catalyze the dismutation of superoxide radicals to hydrogen peroxide and oxygen. The enzyme is ubiquitous in aerobic organisms where it plays a major role in defense against oxygen radical-mediated toxicity. In plants, environmental adversity often leads to the increased generation of reduced oxygen species and, consequently, SOD has been pr...

In self-incompatible (SI) plants, the S locus acts to prevent growth of self-pollen and thus promotes outcrossing within the species. Interspecific crosses between SI and self-compatible (SC) species often show unilateral incompatibility that follows the SI x SC rule: SI species reject pollen from SC species, but the reciprocal crosses are usually compatible. The general validity of the SI x SC...

The light insensitive maize (Zea mays) mutant elongated mesocotyl1 (elm1) has previously been shown to be deficient in the synthesis of the phytochrome chromophore 3E-phytochromobilin (PPhiB). To identify the Elm1 gene, a maize homolog of the Arabidopsis PPhiB synthase gene AtHY2 was isolated and designated ZmHy2. ZmHy2 encodes a 297-amino acid protein of 34 kD that is 50% identical to AtHY2. Z...

We applied the yeast two-hybrid system for screening of a cDNA library of Nicotiana plumbaginifolia for clones encoding plant proteins interacting with two proteins of Escherichia coli: serine acetyltransferase (SAT, the product of cysE gene) and O-acetylserine (thiol)lyase A, also termed cysteine synthase (OASTL-A, the product of cysK gene). Two plant cDNA clones were identified when using the...

We report the presence of an ATP-dependent proteolytic activity in spinach (Spinacia oleracea) leaf mitochondria. The proteolysis was observed as degradation of newly imported precursor protein. The precursor studied was that of the ATP synthase F1 beta subunit of Nicotiana plumbaginifolia, transcribed and translated in vitro. Degradation of pre-F1 beta was observed during kinetic studies of im...