Ammonium assimilation and amino acid metabolism in conifers

Abstract

Conifers are the most important group of gymnosperms, which include tree species of great ecological and economic importance that dominate large ecosystems and play an essential role in global carbon fixation. Nitrogen (N) economy has a special importance in these woody plants that are able to cope with seasonal periods of growth and development over a large number of years. As N availability in the forest soil is extremely low, efficient mechanisms are required for the assimilation, storage, mobilization, and recycling of inorganic and organic forms of N. The cyclic interconversion of arginine and the amides glutamine and asparagine plays a central role in the N metabolism of conifers and the regulation of these pathways is of major relevance to the N economy of the plant. In this paper, details of recent progress in our understanding of the metabolism of arginine and the other major amino acids glutamine, glutamate, aspartate, and asparagine in pine, a conifer model tree, are presented and discussed.

Molecular and Functional Analyses Support a Role of Ornithine-δ-Aminotransferase in the Provision of Glutamate for Glutamine Biosynthesis during Pine Germination

“…Samples were always harvested at the same time in the light/dark cycle. Seven developmental stages were defined as previously described (Cañ as et al, 2007): E0 or dry embryos were sampled from dormant seeds, E1 or imbibed embryos were sampled from seeds after 24 h of being immersed in deionized water, G or germinated embryo were harvested 4 d after imbibition, when the radicle was emerging from the seed. Developmental stages 1 and 2 are seedlings 8 and 12 d after imbibition, respectively, and correspond to early stages where the first needles have not yet developed and the vascular system in the hypocotyl consists of a few poorly lignified vascular bundles.…”

“…SDS-PAGE and electroblotting were carried out as described elsewhere (Cañ as et al, 2007). Membranes were incubated 30 min at room temperature with a 1:5,000 dilution of 6x-His monoclonal antibody from mouse (CLON-TECH) in TPBS (140 mM NaCl, 3 mM KCl, 5 mM Na 2 HPO 4 , 1.47 mM KH 2 PO 4 , pH 7.4, 0.05% [v/v] Tween 20), with 0.05% (w/v) of bovine serum albumin.…”

“…DNA samples were run on 0.8% agarose gel, blotted to nitrocellulose filters, and hybridized to 32 Plabeled probe obtained by labeling the 579-bp cDNA fragment described above with the random primer method (Megaprime; Roche). Prehybridizations, hybridizations, and washes at moderate stringency were performed as described elsewhere (Cañ as et al, 2007).…”

“…Antisense and sense cRNA probes were synthesized by in vitro transcription and labeled with digoxigenin-11-UTP (Roche) following the procedure described by Langdale (1993). Rehydratation, treatment of the sections before hybridization, hybridization, and visualization of signals were carried out exactly as previously described (Cañ as et al, 2007).…”

RESPONSES IN NITROGEN MASS AND NITROGEN METABOLISM OF WILD SUGARCANE (<I>SACCHARUM SPONTANEUM</I> L.) CLONES TO ENHANCED UV-B RADIATION UNDER FIELD CONDITIONS

“…Moreover, reports about intraspecific responses in N metabolism of plants to enhanced ultraviolet-B radiation under field conditions are limited. Nitrate reductase is a key enzyme of N metabolism, which converts nitrate into nitrite on the metabolic pathway leading to the formation of amino acids (Canovas et al, 2007). In wild sugarcane, both roots and foliage participated in NO 3 -reduction (Krywult et al, 2008).…”