Yufang Xu

Novel Benzo-1,2,3-thiadiazole-7-carboxylate Derivatives As Plant Activators and the Development of Their Agricultural Applications

Plant activators are a novel kind of agrochemicals that could induce resistance in many plants against a broad spectrum of diseases. To date, only few plant activators have been commercialized. In order to develop novel plant activators, a series of benzo-1,2,3-thiadiazole-7-carboxylate derivatives were synthesized, and the structures were characterized by (1)H NMR, IR, elemental analyses, and HRMS or MS. Their potential systemic acquired resistance as plant activators was evaluated as well. Most of them showed good activity, especially, fluoro-containing compounds 3d and 3e, which displayed excellent SAR-inducing activity against cucumber Erysiphe cichoracearum and Colletotrichum lagenarium in assay screening. Field test results illustrated that compounds 3d and 3e were more potent than the commercial plant activator, S-methyl benzo[1,2,3]thiadiazole-7-carbothioate (BTH) toward these pathogens. Further, the preparation of compound 3d is more facile than BTH with lower cost, which will be helpful for further applications in agricultural plant protection.

Efficient induction of ginsenoside biosynthesis and alteration of ginsenoside heterogeneity in cell cultures of Panax notoginseng by using chemically synthesized 2-hydroxyethyl jasmonate

Chemically synthesized 2-hydroxyethyl jasmonate (HEJA) was for the first time employed to induce the ginsenoside biosynthesis and to manipulate the product heterogeneity in plant cell cultures. The dose response and timing of HEJA elicitation were investigated in cell suspension cultures of Panax notoginseng. The optimal concentration and timing of HEJA addition for both cell growth and ginsenoside accumulation was identified to be 200xa0μM added on day 4. It was interestingly found that HEJA could stimulate ginsenosides biosynthesis and change their heterogeneity more efficiently than methyl jasmonate (MJA), i.e., the total ginsenoside content and the Rb/Rg ratio increased about 60 and 30% with HEJA elicitation than that by MJA, respectively. The activity of Rb1 biosynthetic enzyme, i.e., UDPG-ginsenoside Rd glucosyltransferase (UGRdGT), was also higher in the former case. A maximal production titer of ginsenoside Rg1, Re, Rb1, and Rd was 47.4±4.8, 52.3±4.4, 190±18, and 12.1±2.5xa0mg/l with HEJA elicitation, which was about 1.3-, 1.3-, 1.7-, and 2.1-fold than that using MJA, respectively. Early signal events in plant defense response, including oxidative burst and jasmonic acid (JA) biosynthesis, were also examined. Levels of H2O2 and NO in medium and l-phenylalanine ammonia lyase activity in cells were not affected by addition of MJA and HEJA. On the other hand, the JA content in cells was increased with external jasmonates elicitation, and it was inhibited with the addition of JA biosynthesis inhibitors. The results suggest that oxidative burst might not be involved in the jasmonates-elicited signal transduction pathway, and MJA and HEJA may induce the ginsenoside biosynthesis via induction of endogenous JA biosynthesis and key enzymes (such as UGRdGT) in the ginsenoside biosynthetic pathway of P. notoginseng cells. The information is useful for hyperproduction of plant-specific heterogeneous products.

Novel chemically synthesized salicylate derivative as an effective elicitor for inducing the biosynthesis of plant secondary metabolites

Trifluoroethyl salicylate (TFESA), a novel salicylate derivative, was chemically synthesized and evaluated by bioassay as a potential elicitor for inducing the biosynthesis of plant secondary metabolites. A cell line of Taxus chinensis, which stably produced a high level of bioactive taxuyunnanine C (Tc), was taken as a model plant cell system. The application of TFESA to the cell cultures could significantly induce Tc biosynthesis, although the cell growth was slightly inhibited. More interestingly, Tc production was enhanced more in the presence of TFESA compared with a structure‐similar well‐known elicitor, salicylic acid (SA). For example, addition of 100 μM TFESA on day 7 led to a high Tc content of 21.9 ± 0.1 mg g−1 (at day 21), whereas the Tc content was 14.0 ± 0.2 and 16.7 ± 0.3 mg g−1 for the control and that with addition of 100 μM SA, respectively. The results indicate that the newly synthesized TFESA can act as a powerful elicitor for secondary metabolism induction in plant cell cultures.

Novel synthetic 2,6-dichloroisonicotinate derivatives as effective elicitors for inducing the biosynthesis of plant secondary metabolites

Two novel 2,6-dichloroisonicotinic acid (INA) derivatives [trifluoroethyl 2,6-dichloroisonicotinate (TFINA) and 2-(2,6-dichloro-pyridine-4-carbonyloxy)-ethyl jasmonate (DPCEJ)] were chemically synthesized and evaluated by bioassay as potential elicitors for inducing the biosynthesis of plant secondary metabolites. A suspension culture of Taxus chinensis, which stably produces a high level of bioactive taxuyunnanine C (Tc), was taken as a model plant cell system. A significant increase in Tc accumulation was observed in the presence of TFINA or DPCEJ. For example, addition of 100xa0μM TFINA or DPCEJ on day 7xa0led to a high Tc content of 21.6±2.0 or 27.7±1.0xa0mg g−1 (on day 21), while the Tc content was 13.7±1.0 and 17.1±0.9xa0mg g−1 for the control and that with addition of 100xa0μM INA, respectively. To the best of our knowledge, this is the first report on the use of synthetic INA derivatives for inducing the biosynthesis of plant secondary metabolites. The results indicate that the newly synthesized INA analogues can act as promising elicitors for secondary metabolism induction in plant cell cultures.

A novel synthetic fluoro-containing jasmonate derivative acts as a chemical inducing signal for plant secondary metabolism

A novel fluoro-containing jasmonate derivative was chemically synthesized and evaluated as a potential elicitor with respect to the induction of plant defense responses and the biosynthesis of plant secondary metabolites. A bioactive taxuyunnanine C (Tc)-producing cell line of Taxus chinensis was taken as a model plant cell system. The presence of novel synthesized pentafluoropropyl jasmonate (PFPJA) induced two early and important events in plant defense responses, including an oxidative burst and activation of l-phenylalanine ammonia lyase. In addition, PFPJA was found to significantly increase Tc accumulation, without any inhibition of cell growth. Moreover, Tc accumulation was increased more in the presence of PFPJA compared with methyl jasmonate (MJA) and previously reported trifluoroethyl jasmonate (TFEJA). For example, addition of 100 μM PFPJA on day 7 led to a high Tc content (38.2±0.3 mg/g) at day 21, while the Tc content was 29.3±0.3 mg/g and 34.9±0.9 mg/g with the addition of 100 μM MJA and TFEJA, respectively. Quantitative structure–activity analysis of fluoro-containing jasmonates suggests that the increase in the fluoro-groups introduced into the carboxyl side-chain of MJA resulted in a higher stimulatory activity for Tc biosynthesis, which corresponds well with the markedly increased lipophilicity after fluorine introduction. These results indicate that newly synthesized fluoro-containing PFPJA can act as a powerful chemical inducing signal for secondary metabolism in plant cell cultures.

CHAPTER 6:Chemical Bioengineering in Plant Cell Culture

Plant secondary metabolites are widely used as valuable medicines, such as paclitaxel, ginsenosides, artemisinin, food additives, and flavors. Plant cell culture technology is a promising alternative method for the mass production of valuable secondary metabolites. Among the manipulative techniques available to promote the productivity of useful secondary metabolites from plant cell cultures, chemical elicitation is one of the best approaches for dramatically increasing secondary metabolite yields. Jasmonic acid (JA) and methyl jasmonate (MJA), derived from linolenic acid, are important natural chemical elicitors. Exogenously adding MJA was shown to enhance production of secondary metabolites in a variety of plant species. Similarly, some synthetic elicitors from plant activators have been proved to be effective in production of secondary metabolites. In this chapter, we describe cell culture processes promoted by a series of synthetic elicitors, including MJA derivatives and benzothiadiazole derivatives, which we describe as chemical biotechnology and bioengineering. The results show that these synthetic elicitor derivatives greatly promote valuable secondary metabolites production in both Taxus chinensis and Panax notoginseng culture cells, which lays the foundation for the industrial application of valuable secondary metabolites (taxanes and ginsenosides).