Isolation and characterization of [delta]9 stearoyl-acyl carrier protein desaturase gene from Glycine max

Fatty acid biosynthesis in plants occurs in the chloroplasts of green tissue and in the plastids of nonphotosynthetic tissues. In most plants, the primary products of fatty acid synthesis are palmitoyl-acyl-carrier protein (ACP) (16:0-ACP) and stearoyl-ACP desaturase (EC 1.14.99.6), introduces the first double bond into stearoyl-ACP between carbons 9 and 10 to produce oleoyl-ACP (18:1-ACP). Additional double bonds are introduced into oleic acid or palmitic acid after incorporation of the fatty acids into lipids. Since most plants lack any other desaturase that acts on 18:0, the level of stearoyl-ACP desaturase activity is a key determinant of the overall level of fatty acid desaturation. As a first step toward understanding the reaction mechanism and the regulation of stearoyl-ACP desaturation, we have undertaken isolation and characterization of cDNA clones encoding the stearoyl-ACP desaturase from soybean mutant A6, which showed reduced desaturase activity compared to its parent soybean FA8077. A6 showed altered phenotypes, e.g., smaller in height, delayed blooming pattern, and smaller seed sizes. Sequencing of a cDNA clone was completed and genomic clones were isolated from [Lambda]gt 1O derivative [Lambda]GEMII library. Genomic DNA fragments containing a gene encoding desaturase from FA8077 and A6 were also obtained and sequenced. There were two sequence differences between these two strains in coding region of the desaturase. One of the altered nucleic acids caused one amino acid change at the electron transfer domain of the desaturase in A6. Desaturase enzyme assay in vitro with altered nucleic acids showed reduced desaturase activity

Treatment with Calcium Chloride Enhances Water Deficit Stress Tolerance in Viola (Viola cornuta)

Water deficit stress can reduce the postproduction shelf life and marketability of floriculture crops. To alleviate the damage by water deficiency, plants need to limit transpirational water loss by inducing stomatal closure. Osmotic stress induces stomatal closure like the response to water deficit stress. It could be used as a convenient tool to enhance water deficit stress tolerance by reducing water loss. The objective of this research was to investigate whether osmotic treatment with a high concentration of chemical solutions could trigger a response to osmotic stress so that stomatal closure can be induced, resulting in enhanced water deficit stress tolerance in viola (Viola cornuta ‘Sorbet XP Yellow’). Osmotic treatments with CaCl2, Ca(NO3)2, NaCl, NaNO3, BaCl2, Ba(NO3)2, and mannitol were applied at the osmotic potentials (cS) of L1.3 and L2.0 MPa. Chemical treatments [except Ca(NO3)2, NaCl, and mannitol] helped to delay wilting and gave a longer shelf life, up to 5.2 days over that of the control, 2.5 days. However, leaf necrosis was observed on the violas treated with NaCl, NaNO3, BaCl2, Ba(NO3)2, and mannitol. CaCl2 was the most effective agent in delaying wilting under water deficit stress in viola without leaf necrosis. Compared with the control, violas treated with CaCl2 at 200 and 300 mM showed an increase in shelf life by 2.6 and 1.2 days, respectively. Stomatal conductance (gS) was reduced within 4 hours after treatment with CaCl2 compared with that of control violas. Leaf relative water content (RWC) of control violas was dramatically reduced 3 days after treatment and fell below 50% on day 4, while CaCl2-treated violas maintained higher leaf RWC (70% to 81%) during the water deficit period. These results indicated that osmotic treatment with the high concentration of CaCl2 caused stomatal closure, resulting in a reduction of water loss and an extension of shelf life under water deficit stress in viola

Glycogen Synthase Isoforms in Synechocystis sp. PCC6803: Identification of Different Roles to Produce Glycogen by Targeted Mutagenesis.

Synechocystis sp. PCC6803 belongs to cyanobacteria which carry out photosynthesis and has recently become of interest due to the evolutionary link between bacteria and plant species. Similar to other bacteria, the primary carbohydrate storage source of Synechocystis sp. PCC6803 is glycogen. While most bacteria are not known to have any isoforms of glycogen synthase, analysis of the genomic DNA sequence of Synechocystis sp. PCC6803 predicts that this strain encodes two isoforms of glycogen synthase (GS) for synthesizing glycogen structure. To examine the functions of the putative GS genes, each gene (sll1393 or sll0945) was disrupted by double cross-over homologous recombination. Zymogram analysis of the two GS disruption mutants allowed the identification of a protein band corresponding to each GS isoform. Results showed that two GS isoforms (GSI and GSII) are present in Synechocystis sp. PCC6803, and both are involved in glycogen biosynthesis with different elongation properties: GSI is processive and GSII is distributive. Total GS activities in the mutant strains were not affected and were compensated by the remaining isoform. Analysis of the branch-structure of glycogen revealed that the sll1393− mutant (GSI−) produced glycogen containing more intermediate-length chains (DP 8–18) at the expense of shorter and longer chains compared with the wild-type strain. The sll0945− mutant (GSII−) produced glycogen similar to the wild-type, with only a slightly higher proportion of short chains (DP 4–11). The current study suggests that GS isoforms in Synechocystis sp. PCC6803 have different elongation specificities in the biosynthesis of glycogen, combined with ADP-glucose pyrophosphorylase and glycogen branching enzyme

Biofortification of Sodium Selenate Improves Dietary Mineral Contents and Antioxidant Capacity of Culinary Herb Microgreens

Selenium biofortification of plants has been suggested as a method of enhancing dietary seleniumintake to prevent deficiency and chronic disease in humans, while avoiding toxic levels of intake. Popular herbs such as basil (Ocimum basilicum L.), cilantro (Coriandrum sativum L.), and scallions (Allium fistulosum L.) present an opportunity for biofortification as these plants are used for added flavors to meals and are available as microgreens, young plants with increasing popularity in the consumer marketplace. In this study, basil, cilantro, and scallion microgreens were biofortified with sodium selenate under hydroponic conditions at various selenium concentrations to investigate the effects on yield, selenium content, other mineral contents (i.e., sodium, potassium, calcium, magnesium, phosphorus, copper, zinc, iron, manganese, sulfur, and boron), total phenol content, and antioxidant capacity [oxygen radical absorbance capacity (ORAC)]. The results showed that the selenium content increased significantly at all concentrations, with scallions demonstrating the largest increase. The effects on other minerals varied among herb species. Antioxidant capacity and total phenol content increased in all herbs at the highest selenium treatments, but basil and scallions demonstrated a decreased crop yield. Overall, these biofortified culinary herbmicrogreens are an ideal functional food for enhancing selenium, other dietary minerals, and antioxidants to benefit human health

Isolation and characterization of [delta]9 stearoyl-acyl carrier protein desaturase gene from Glycine max

Fatty acid biosynthesis in plants occurs in the chloroplasts of green tissue and in the plastids of nonphotosynthetic tissues. In most plants, the primary products of fatty acid synthesis are palmitoyl-acyl-carrier protein (ACP) (16:0-ACP) and stearoyl-ACP desaturase (EC 1.14.99.6), introduces the first double bond into stearoyl-ACP between carbons 9 and 10 to produce oleoyl-ACP (18:1-ACP). Additional double bonds are introduced into oleic acid or palmitic acid after incorporation of the fatty acids into lipids. Since most plants lack any other desaturase that acts on 18:0, the level of stearoyl-ACP desaturase activity is a key determinant of the overall level of fatty acid desaturation. As a first step toward understanding the reaction mechanism and the regulation of stearoyl-ACP desaturation, we have undertaken isolation and characterization of cDNA clones encoding the stearoyl-ACP desaturase from soybean mutant A6, which showed reduced desaturase activity compared to its parent soybean FA8077. A6 showed altered phenotypes, e.g., smaller in height, delayed blooming pattern, and smaller seed sizes. Sequencing of a cDNA clone was completed and genomic clones were isolated from [Lambda]gt 1O derivative [Lambda]GEMII library. Genomic DNA fragments containing a gene encoding desaturase from FA8077 and A6 were also obtained and sequenced. There were two sequence differences between these two strains in coding region of the desaturase. One of the altered nucleic acids caused one amino acid change at the electron transfer domain of the desaturase in A6. Desaturase enzyme assay in vitro with altered nucleic acids showed reduced desaturase activity.</p