Decreased Growth Temperature Increases Soybean Stearoyl-Acyl Carrier Protein Desaturase Activity

Abstract

Developing soybean (Glycine max) seeds respond to a change in growth temperature by changing the level of stearoyl acyl carrier protein desaturase activity in the tissue. After 20 hours in liquid culture, seeds grown at 200C show an increase in activity while seeds grown at 35°C show a decrease in activity, relative to their preculture levels. Analysis of the enzyme from both growth conditions shows the change not to be due to induction of kinetically distinct iosenzymes; desaturase activities from both 200C and 350C have identical behavior with regard to pH, temperature optimum, substrate concentration and cofactor requirements. Experiments with boiled extracts indicate that the modulation is not caused by induction of metabolic effectors. From these data, it appears that stearoyl-acyl carrier protein desaturase responds to changes in growth temperature by altering the level of active enzyme present in the tissue. The magnitude of this response is a function of the developmental stage of the seed and not a function of the growth conditions of the parent plant. Changing the age of the seeds from early late R5 changed the ratio of 20:350C activity from 3.8:1 to 1.2:1. Changing the temperature at which the parent plants were grown over a range from 20/120C to 34/280C (day/night) produced only minor, and inconsistent, changes in the ratio of 20:350C activities.Plants respond to changes in environmental temperature by altering their fatty acid composition (7-9). In mature soybean seeds the fatty acid composition of both phospholipids (4) and triglycerides (18) that begins with stearoyl-ACP desaturase. Therefore, any changes in this enzyme could lead to a change in the ratio of saturated to unsaturated fatty acids in the tissue (6). In developing soybean seeds, stearoyl-ACP desaturase activity is low compared to the in vitro activity of the other enzymes of fatty acid synthesis and desaturation (2).The absence of other A-9 desaturases in soybean ( 17), the low activity in vitro, and the modulation of activity by growth temperature (2) all suggest that this enzyme may play an important role in the regulation of fatty acid desaturation in developing soybean seeds. More information is needed on how this enzyme is regulated and what role it may play in controlling fatty acid desaturation. This report concerns the mechanism by which stearoyl-ACP desaturase responds to changes in growth temperature and some possible factors that may affect the magnitude of this response. MATERIALS AND METHODS MaterialsThe [9,1 0-3H]stearic acid was purchased from Amersham. All other reagents and solvents were from Sigma Chemical Co. or EM Science. ACP was purified from log phase Escherichia coli (Grain Processors Inc.) by the method of Rock and Cronan (14). [9, (13). The resulting pod cultures were incubated for 20 h at either 20°C or 35°C. Seeds were harvested from the cultures and crude enzyme extracts were prepared as previously described (2). Extracts were either used directly or stored at -80°C. Frozen extracts were stable ...

Functionality of soybean CBF/DREB1 transcription factors

“…In unifoliate leaves from young soybean seedlings, transcripts of the GmCBF-like genes, [GmDREB1A;1 (Glyma09g27180), GmDREB1A;2 (Glyma16g32330), GmDREB1B;1 (Glyma20g29410), and GmDREB1B;2 (Glyma10g38440); as well as GmDREB1C;1 (Glyma01g42500), GmDREB1D;2 (Glyma17g14111), and GmDREB1D;1 (Glyma05g03560)] were significantly accumulated by 1 h after cold treatment (adjusted P-value <0.001) ( Figure 3). By 24 h of cold treatment, transcripts of four GmCBF genes (GmDREB1A;1, GmDREB1A;2, GmDREB1C;1 and GmDREB1D; 1) had significantly decreased compared to 1 h but still sustained levels substantially 13 above the 0 h time control level (adjusted P-value <0.001). None of the soybean genes similar to AtDREB2 or 3 were up-regulated at 1 h cold treatment, indicating that the GmCBF/DREB1 gene group are the immediate cold responsive genes acting as primary cold transcription factors ( Figure 3).…”

“…Soybean is chilling and cold/freezing intolerant [1][2][3][4] with severe damage occurring at temperatures proximal to freezing. In the field, little growth occurs at temperatures below 6-7 °C [5], and cool temperatures at the end of the growing season are a major limiting factor in soybean yield and production [6].…”

Responses of Nannochloropsis oceanica IMET1 to Long-Term Nitrogen Starvation and Recovery

“…Values are based on three biological replicates. Further information regarding the protein identification is accessible at Supplemental of plant (Cheesbrough, 1990;Fukuchi-Mizutani et al, 1998). In 18:3-type plants, all unsaturated fatty acids are synthesized by the pathway that begins with stearoyl-ACP desaturase (Cheesbrough, 1990).…”

Modifying Vegetable Oils for Food and Non-food Purposes

“…The concentration of the cardiovascular ''neutral'' saturated fatty acid, stearate, in soybean is controlled by both desaturase (Cheesbrough 1990) and thioesterase activities (Pantalone et al 2002). The genetic locus controlling elevated stearic acid levels in soybean, is designated Fas, and allelic variation at this locus manifests stearic acid levels ranging from wild type concentrations of 3%, up to high stearate germplasm with 35% (Bubeck et al 1989;Rahman et al 1995;Pantalone et al 2002).…”