Metabolic changes of Brassica rapa transformed with a bacterial isochorismate synthase gene

Abiotic stress-induced secondary metabolite production in Brassica: opportunities and challenges

Over the decades, extensive research efforts have been undertaken to understand how secondary plant metabolites are affected by genetic, environmental, and agronomic factors. Understanding the genetic basis of stress-response metabolite biosynthesis is crucial for sustainable agriculture production amidst frequent occurrence of climatic anomalies. Although it is known that environmental factors influence phytochemical profiles and their content, studies of plant compounds in relation to stress mitigation are only emerging and largely hindered by phytochemical diversities and technical shortcomings in measurement techniques. Despite these challenges, considerable success has been achieved in profiling of secondary metabolites such as glucosinolates, flavonoids, carotenoids, phenolic acids and alkaloids. In this study, we aimed to understand the roles of glucosinolates, flavonoids, carotenoids, phenolic acids and alkaloids in relation to their abiotic stress response, with a focus on the developing of stress-resilient crops. The focal genus is the Brassica since it (i) possesses variety of specialized phytochemicals that are important for its plant defense against major abiotic stresses, and (ii) hosts many economically important crops that are sensitive to adverse growth conditions. We summarize that augmented levels of specialized metabolites in Brassica primarily function as stress mitigators against oxidative stress, which is a secondary stressor in many abiotic stresses. Furthermore, it is clear that functional characterization of stress-response metabolites or their genetic pathways describing biosynthesis is essential for developing stress-resilient Brassica crops.

Development of Transgenic Brassica Crops Against Biotic Stresses Caused by Pathogens and Arthropod Pests

The Brassica genus includes one of the 10 most agronomically and economically important plant groups in the world. Within this group, we can find examples such as broccoli, cabbage, cauliflower, kale, Brussels sprouts, turnip or rapeseed. Their cultivation and postharvest are continually threatened by significant stresses of biotic origin, such as pathogens and pests. In recent years, numerous research groups around the world have developed transgenic lines within the Brassica genus that are capable of defending themselves effectively against these enemies. The present work compiles all the existing studies to date on this matter, focusing in a special way on those of greater relevance in recent years, the choice of the gene of interest and the mechanisms involved in improving plant defenses. Some of the main transgenic lines developed include coding genes for chitinases, glucanases or cry proteins, which show effective results against pathogens such as Alternaria brassicae, Leptosphaeria maculans or Sclerotinia sclerotiorum, or pests such as Lipaphis erysimi or Plutella xylostella.

Isolation and characterization of isochorismate synthase and cinnamate 4-hydroxylase during salinity stress, wounding, and salicylic acid treatment in Carthamus tinctorius

Salicylic acid (SA) is a prominent signaling molecule during biotic and abiotic stresses in plants biosynthesized via cinnamate and isochorismate pathways. Cinnamate 4-hydroxylase (C4H) and isochorismate synthase (ICS) are the main enzymes in phenylpropanoid and isochorismate pathways, respectively. To investigate the actual roles of these genes in resistance mechanism to environmental stresses, here, the coding sequences of these enzymes in safflower (Carthamus tinctorius), as an oilseed industrial medicinal plant, were partially isolated and their expression profiles during salinity stress, wounding, and salicylic acid treatment were monitored. As a result, safflower ICS (CtICS) and C4H (CtC4H) were induced in early time points after wounding (3-6 h). Upon salinity stress, CtICS and CtC4H were highly expressed for the periods of 6-24 h and 3-6 h after treatment, respectively. It seems evident that ICS expression level is SA concentration dependent as if safflower treatment with 1 mM SA could induce ICS much stronger than that with 0.1 mM, while C4H is less likely to be so. Based on phylogenetic analysis, safflower ICS has maximum similarity to its ortholog in Vitis vinifera up to 69%, while C4H shows the highest similarity to its ortholog in Echinacea angustifolia up to 96%. Overall, the isolated genes of CtICS and CtC4H in safflower could be considered in plant breeding programs for salinity tolerance as well as for pathogen resistance.

Metabolic fingerprinting of Tomato Mosaic Virus infected Solanum lycopersicum

(1)H nuclear magnetic resonance (NMR)-based metabolomics has been applied to study the compatible interaction between tomato plants and Tomato Mosaic Virus (ToMV). A detailed time course of metabolic fingerprinting of ToMV-inoculated and non-inoculated systemically infected tomato leaves has provided a fundamental understanding of the metabolic state of the plant not only in response to ToMV infection, but also under various physiological conditions. By this analytical platform a total of 32 metabolites including amino/organic acids, sugars, phenylpropanoids, flavonoids and other miscellaneous compounds were detected. Using multivariate data analysis, we have identified a subset of metabolites induced during the plant defence response and metabolites whose accumulation was dependent on the developmental stage, the position of the leaf on the stem, and the harvesting time. Specifically, a general time-dependent decrease in organic acids, amino acids (excluding asparagine), phenylpropanoids and rutin was observed in individual leaves. In addition, metabolite alterations were also found to correlate with the developmental stage of the leaf: high levels of organic acids, some amino acids, phenylpropanoids, and flavonoids were found in lower leaves while elevated amounts of sugars were present in the upper ones. Moreover, a marked variation in the content of some metabolites was also observed to be associated to the asymptomatic ToMV infection both in inoculated and systemically infected leaves. While flavonoids accumulated in virus-inoculated leaves, increased levels of phenylpropanoids were observed in non-inoculated leaves where ToMV actively replicates. Finally, diurnal changes in the metabolite content were also observed: an increase of amino acids and organic acids (except glutamic acid) were observed in the samples collected in the morning, whereas sugars and secondary metabolite levels increased in the tomato leaves harvested in the evening.