@Article{IPB-2207, author = {Feussner, I. and Kühn, H. and Wasternack, C. and}, title = {{Lipoxygenase-dependent degradation of storage lipids}}, year = {2001}, pages = {268-273}, journal = {Trends Plant Sci.}, doi = {10.1016/S1360-1385(01)01950-1}, volume = {6}, abstract = {Oilseed germination is characterized by the mobilization of storage lipids as a carbon source for the germinating seedling. In spite of the importance of lipid mobilization, its mechanism is only partially understood. Recent data suggest that a novel degradation mechanism is initiated by a 13-lipoxygenase during germination, using esterified fatty acids specifically as substrates. This 13-lipoxygenase reaction leads to a transient accumulation of ester lipid hydroperoxides in the storage lipids, and the corresponding oxygenated fatty acid moieties are preferentially removed by specific lipases. The free hydroperoxy fatty acids are subsequently reduced to their hydroxy derivatives, which might in turn undergo β-oxidation.} } @Article{IPB-2195, author = {BERGER, S. and Weichert, H. and Porzel, A. and Wasternack, C. and Kühn, H. and Feussner, I. and}, title = {{Enzymatic and non-enzymatic lipid peroxidation in leaf development}}, year = {2001}, pages = {266-276}, journal = {BBA-Mol. Cell Biol. Lipids}, doi = {10.1016/S1388-1981(01)00161-5}, volume = {1533}, abstract = {Enzymatic and non-enzymatic lipid peroxidation has been implicated in programmed cell death, which is a major process of leaf senescence. To test this hypothesis we developed a high-performance liquid chromatography (HPLC) method for a simultaneous analysis of the major hydro(pero)xy polyenoic fatty acids. Quantities of lipid peroxidation products in leaves of different stages of development including natural senescence indicated a strong increase in the level of oxygenated polyenoic fatty acids (PUFAs) during the late stages of leaf senescence. Comprehensive structural elucidation of the oxygenation products by means of HPLC, gas chromatography/mass spectrometry and 1H nuclear magnetic resonance suggested a non-enzymatic origin. However, in some cases a small share of specifically oxidized PUFAs was identified suggesting involvement of lipid peroxidizing enzymes. To inspect the possible role of enzymatic lipid peroxidation in leaf senescence, we analyzed the abundance of lipoxygenases (LOXs) in rosette leaves of Arabidopsis. LOXs and their product (9Z,11E,13S,15Z)-13-hydroperoxy-9,11,15-octadecatrienoic acid were exclusively detected in young green leaves. In contrast, in senescing leaves the specific LOX products were overlaid by large amounts of stereo-random lipid peroxidation products originating from non-enzymatic oxidation. These data indicate a limited contribution of LOXs to total lipid peroxidation, and a dominant role of non-enzymatic lipid peroxidation in late stages of leaf development.} } @Article{IPB-2236, author = {Weichert, H. and Kohlmann, M. and Wasternack, C. and Feussner, I. and}, title = {{Metabolic profiling of oxylipins upon sorbitol treatment in barley leaves}}, year = {2001}, pages = {861-862}, journal = {Biochem. Soc. Trans.}, doi = {10.1042/bst0280861}, volume = {28}, abstract = {In barley leaves 13-lipoxygenases (LOXs) are induced by salicylate and jasmonate. Here, we analyse by metabolic profiling the accumulation of oxylipins upon sorbitol treatment. Although 13-LOX-derived products are formed and specifically directed into the reductase branch of the LOX pathway, accumulation is much later than in the cases of salicylate and jasmonate treatment. In addition, under these conditions only the accumulation of jasmonates as additional products of the LOX pathway has been found.} } @Article{IPB-2233, author = {Ticconi, C. A. and Delatorre, C. A. and Abel, S. and}, title = {{Attenuation of Phosphate Starvation Responses by Phosphite in Arabidopsis}}, year = {2001}, pages = {963-972}, journal = {Plant Physiol.}, doi = {10.1104/pp.010396}, volume = {127}, abstract = {When inorganic phosphate is limiting, Arabidopsis has the facultative ability to metabolize exogenous nucleic acid substrates, which we utilized previously to identify insensitive phosphate starvation response mutants in a conditional genetic screen. In this study, we examined the effect of the phosphate analog, phosphite (Phi), on molecular and morphological responses to phosphate starvation. Phi significantly inhibited plant growth on phosphate-sufficient (2 mm) and nucleic acid-containing (2 mmphosphorus) media at concentrations higher than 2.5 mm. However, with respect to suppressing typical responses to phosphate limitation, Phi effects were very similar to those of phosphate. Phosphate starvation responses, which we examined and found to be almost identically affected by both anions, included changes in: (a) the root-to-shoot ratio; (b) root hair formation; (c) anthocyanin accumulation; (d) the activities of phosphate starvation-inducible nucleolytic enzymes, including ribonuclease, phosphodiesterase, and acid phosphatase; and (e) steady-state mRNA levels of phosphate starvation-inducible genes. It is important that induction of primary auxin response genes by indole-3-acetic acid in the presence of growth-inhibitory Phi concentrations suggests that Phi selectively inhibits phosphate starvation responses. Thus, the use of Phi may allow further dissection of phosphate signaling by genetic selection for constitutive phosphate starvation response mutants on media containing organophosphates as the only source of phosphorus.} } @Article{IPB-2221, author = {Li, G. and Riaz, A. and Goyal, S. and Abel, S. and Quiros, C. F. and}, title = {{Inheritance of Three Major Genes Involved in the Synthesis of Aliphatic Glucosinolates in Brassica oleracea}}, year = {2001}, pages = {427-431}, journal = {J. Am. Soc. Hortic. Sci.}, doi = {10.21273/JASHS.126.4.427}, volume = {126}, abstract = {Inheritance of three major genes involved in synthesis of aliphatic glucosinolates (GSL) was followed in segregating populations of Brassica oleracea L. generated from three crosses: broccoli × cauliflower, collard × broccoli, and collard × cauliflower. Two of these genes, GSL-PRO and GSL-ELONG, regulate sidechain length. The action of the former results in three-carbon GSL, whereas action of the latter produces four-carbon GSL. We determined that these two genes act and segregate independently from each other in B. oleracea. The double recessive genotype produces only trace amounts of aliphatic GSL. The third gene, GSL-ALK controls sidechain desaturation and, as it has been observed in Arabidopsis thaliana (L.) Heynh., we found that this gene cosegregates with a fourth gene, GSL-OH, that is responsible for sidechain hydroxylation. Elucidation of the inheritance of major genes controlling biosynthesis of GSL will allow for manipulation of these genes and facilitate development of lines with specific GSL profiles. This capability will be important for improvement of Brassica breeding lines with high content of desirable GSL, like glucoraphanin, a demonstrated precursor of anticarcinogenic compounds. Additionally, this work is the first step towards cloning the major genes of the aliphatic GSL pathway, and to use these clones in transformation strategies for further crop enhancement.} } @Article{IPB-2214, author = {Hilpert, B. and Bohlmann, H. and Den Camp, R. o. and Przybyla, D. and Miersch, O. and Buchala, A. and Apel, K. and}, title = {{Isolation and characterization of signal transduction mutants of Arabidopsis thaliana that constitutively activate the octadecanoid pathway and form necrotic microlesions}}, year = {2001}, pages = {435-446}, journal = {Plant J.}, doi = {10.1046/j.1365-313X.2001.2641036.x}, volume = {26}, abstract = {Thionins are a group of antimicrobial polypeptides that form part of the plant\'s defense mechanism against pathogens. The Thi 2.1 thionin gene of Arabidopsis thaliana has been shown to be inducible by jasmonic acid (JA), an oxylipin‐like hormone derived from oxygenated linolenic acid and synthesized via the octadecanoid pathway. The JA‐dependent regulation of the Thi 2.1 gene has been exploited for setting up a genetic screen for the isolation of signal transduction mutants that constitutively express the Thi 2.1 gene. Ten cet‐mutants have been isolated which showed a c onstitutive e xpression of the t hionin gene. Allelism tests revealed that they represent at least five different loci. Some mutants are dominant, others recessive, but all cet mutations behaved as monogenic traits when backcrossed with Thi 2.1‐GUS plants. Some of the mutants overproduce JA and its bioactive precursor 12‐oxophytodienoic acid (OPDA) up to 40‐fold while others have the same low levels as the control wildtype plants. Two of the mutants showed a strong induction of both the salicylic acid (SA)‐ and the JA‐dependent signaling pathways, while the majority seems to be affected only in the octadecanoid pathway. The Thi 2.1 thionin gene and the Pdf 1.2 defensin gene are activated independently, though both are regulated by JA. The cet‐mutants, except for one, also show a spontaneous leaf cell necrosis, a reaction often associated with the systemic acquired resistance (SAR) pathway.} } @INBOOK{IPB-161, author = {Abel, S. and Köck, M. and}, title = {{Ribonucleases - Part A}}, year = {2001}, pages = {351-368}, chapter = {{Secretory Acid Ribonucleases from Tomato, Lycopersicon esculentum Mill.}}, journal = {Methods Enzymol.}, doi = {10.1016/S0076-6879(01)41163-3}, volume = {341}, }