Shikimic acid accelerates phase change and flowering in Chinese jujube

The juvenile-to-adult phase change with first flowering as the indicator plays a crucial role in the lifecycle of fruit trees. However, the molecular mechanisms underlying phase change in fruit trees remain largely unknown. Shikimic acid (ShA) pathway is a main metabolic pathway closely related to the synthesis of hormones and many important secondary metabolites participating in plant phase change. So,whether ShA regulates phase change in plants is worth clarifying. Here, the distinct morphological characteristics and the underlying mechanisms of phase change in jujube (Ziziphus jujuba Mill.), an important fruit tree native to China with nutritious fruit and outstanding tolerance abiotic stresses, were clarified. A combined transcriptome and metabolome analysis found that ShA is positively involved in jujube(Yuhong’×Xing 16’) phase change. The genes in the upstream of ShA synthesis pathway (ZjDAHPS, ZjDHQS and ZjSDH), the contents of ShA and the downstream secondary metabolites like phenols were significantly upregulated in the phase change period. Further, the treatment of spraying exogenous ShA verified that ShA at a very low concentration (60 mg·L^(-1)) can substantially speed up the phase change and flowering of jujube and other tested plants including Arabidopsis, tomato and wheat. The exogenous ShA (60 mg·L^(-1)) treatment in jujube seedlings could increase the accumulation of endogenous ShA, enhance leaf photosynthesis and the synthesis of phenols especially flavonoids and phenolic acids, and promote the expression of genes (ZjCOs, ZjNFYs and ZjPHYs) involved in flowering pathway. Basing on above results, we put forward a propose for the underlying mechanism of ShA regulating phase change, and a hypothesis that ShA could be considered a phytohormone-like substance because it is endogenous, ubiquitous, movable and highly efficient at very low concentrations. This study highlights the critical role of ShA in plant phase change and its phytohormone-like properties.

Facile Syntheses of (6S)-6-Fluoroshikimic Acid and (6R)-6-Hydroxyshikimic Acid

(6S)-6-Fluoroshikimic acid 2 and (6 R ) 6 hydroxyshikimic acid 3 have been synthesized via an OsO 4 catalysed dihydroxylation of diene 7, which was derived from (-) shikimic acid 1.

Enhanced production of shikimic acid using a multi-gene co-expression system in Escherichia coli

Shikimic acid(SA) is the key synthetic material for the chemical synthesis of Oseltamivir, which is prescribed as the front-line treatment for serious cases of influenza. Multi-gene expression vector can be used for expressing the plurality of the genes in one plasmid, so it is widely applied to increase the yield of metabolites. In the present study, on the basis of a shikimate kinase genetic defect strain Escherichia coli BL21(?aro L/aro K, DE3), the key enzyme genes aro G, aro B, tkt A and aro E of SA pathway were co-expressed and compared systematically by constructing a series of multi-gene expression vectors. The results showed that different gene co-expression combinations(two, three or four genes) or gene orders had different effects on the production of SA. SA production of the recombinant BL21-GBAE reached to 886.38 mg·L^(-1), which was 17-fold(P < 0.05) of the parent strain BL21(?aro L/aro K, DE3).

Improved Stereoselective Syntheses of （-t-）-Valiolamine and （-I-）-Valienamine Starting from （-）-Shikimic Acid

Improved stereoselective syntheses of the targeted compounds （＋）-valiolamine 1 and （＋）-valienamine 2 starting from naturally abundant （–）-shikimic acid are described. A common key intermediate compound 7 was first synthesized from （–）-shikimic acid in 9 steps. The compound 7 was then converted to （＋）-valiolamine 1 in 3 steps, and was also converted to （＋）-valienamine 2 in 4 steps. In summary, （＋）-valiolamine 1 and （＋）-valienamine 2 were synthesized from （–）-shikimic acid in 12 （or 13） steps in 40% and 39% overall yields, respectively.

Changes of chlorogenic acid content and its synthesis-associated genes expression in Xuehua pear fruit during development

According to synthetic pathway of plant chlorogenic acid （CGA）, the expression patterns of genes encoding enzymes that are associated with CGA synthesis were studied in normally developed Xuehua pear fruit. The study demonstrated that CGA content in peel and flesh of Xuehua pear decreased as fruit development progressed, with a higher level in peel. The expression levels of PbPAL 1, PbPAL2, PbC3H, PbC4H, Pb4CL 1, Pb4CL2, Pb4CL6, PbHC T1 and PbHC T3 genes decreased in fruit, which was consistent with the pattern of variation in CGA content. That indicated that these genes might be key genes for influencing fruit CGA synthesis in Xuehua pear. However, Pb4CL7 gene expression profile is not consistent with variation of CGA content, hence, it may not be a key gene involved in CGA synthesis.

Occurrence of Glyphosate-Resistant Horseweed (Conyza canadensis) Population in China

Horseweed （Conyza canadensis）, an invasive alien weed, is one of the main weeds in orchards in China. Although glyphosate has been used for control of horseweed and many other weeds in orchards for more than 25 years in China, a case of glyphosate-resistant horseweed has not been identified in orchard in China so far despite glyphosate-resistant horseweed cases have been reported in some other countries. Seeds of 25 horseweed populations were collected from different orchards with different glyphosate application history. Potted seedlings with 11-13-leaf growth stage were treated with glyphosate at 0.035, 0.07, 0.14, 0.28, 0.56, 1.12, 2.24, 4.48, and 8.96 kg a.i. ha-1. The dosage dependence response curve of each population was constructed with Log-logistic dose response regression equations. The ED50 value of each population was calculated and compared with the susceptible population from China. Different populations had different relative glyphosate-resistant levels which increased with the number of years of glyphosate application. Two populations with the highest resistance levels, 8.28 and 7.95 times, were found in Ningbo, Zhejiang Province, China, where glyphosate was used for weed control in orchards twice each year for 15 yr. The two resistant populations accumulated approximately two to four times less shikimic acid than the two susceptible populations 48 h after glyphosate application.

Glyphosate Effects on Sugarcane Metabolism and Growth

Glyphosate is the most widely used herbicide in the world. In sugarcane, it is used as a herbicide when applied at its field rate, but it is also used as ripener when applied as low doses. However, the effects of glyphosate on plant metabolism and sugarcane growth are not fully understood. This study aimed to evaluate the metabolic changes and the effects on sugarcane plant growth caused by the application of different doses of glyphosate. Sugarcane plants were grown in a greenhouse and subjected to glyphosate applications at doses of 7.2;18;36;72;180;360 and 720 g a.e. ha-1. Plants grown without an herbicide application were used as a control. Plants from each treatment were collected at 2, 7, 14, and 21 days after treatment (DAT) application to quantify the levels of shikimic acid, quinic acid, shikimate-3-phosphate, glyphosate, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), phenylalanine, tyrosine, and tryptophan. Visual evaluations of plant intoxication were performed at the same time as the collection of plants, and the quantification of their shoot dry biomass was performed at 21 DAT. At doses of glyphosate greater than 72 g a.e. ha-1, increases in the levels of shikimic acid, quinic acid, and shikimate-3-phosphate occurred and AMPA was detected in the plants. Initially, glyphosate caused increases in the plant levels of phenylalanine and tyrosine at doses of 72 and 180 g a.e. ha-1, although a decrease in the levels of aromatic amino acids subsequently occurred at and above the doses of 72 or 180 g a.e. ha-1. The doses ranging from 7.2 to 36 g a.e. ha-1 promoted an increase in plant shoot biomass, and doses greater than 72 g a.e. ha-1 caused significant reductions in dry mass.

Enantioselective Total Synthesis of the (+) Antipode of Zeylenone

Starting from shikimic acid, the total synthesis of zeylenone was studied. The productwas proved to be the (+)antipode of zeylenone through analysis and comparison of their respectivespectra (including NMR, MS, IR and CD) and optical data. The absolute configuration of thenatural product was thus determined to be (1S,2S,3R).

Novel and Efficient Syntheses of Four Useful Shikimate- derived Epoxy Chiral Building Blocks via Cyclic Sulfite Intermediates

All of the four stereoisomers of methyl 4,5-epoxy-3-hydroxy-cyclohex-l-ene-carboxylate （la--ld） are useful chiral building blocks. Novel and efficient syntheses of these four epoxy chiral building blocks from naturally abun- dant （--）-shikimic acid （2） via cyclic sulfite intermediates are described in this article. The targeted compound （3R,4R,5S）-la was synthesized via four steps from （--）-shikimic acid in 79% overall yield. The other three targeted compounds （3S,4R,5S）-lb, （3S,4S,5R）-1c and （3R,4S,5R）-ld were synthesized via seven steps from （--）-shikimic acid in 56%, 64% and 65% overall yields, respectively.