Metabolic activities and molecular investigations of the ameliorative impact of some growth biostimulators on chilling-stressed coriander (Coriandrum sativum L.) plant.

BACKGROUND: Priming of seed prior chilling is regarded as one of the methods to promote seeds germination, whole plant growth, and yield components. The application of biostimulants was reported as beneficial for protecting many plants from biotic or abiotic stresses. Their value was as important to be involved in improving the growth parameters of plants. Also, they were practiced in the regulation of various metabolic pathways to enhance acclimation and tolerance in coriander against chilling stress. To our knowledge, little is deciphered about the molecular mechanisms underpinning the ameliorative impact of biostimulants in the context of understanding the link and overlap between improved morphological characters, induced metabolic processes, and upregulated gene expression. In this study, the ameliorative effect(s) of potassium silicate, HA, and gamma radiation on acclimation of coriander to tolerate chilling stress was evaluated by integrating the data of growth, yield, physiological and molecular aspects. RESULTS: Plant growth, yield components, and metabolic activities were generally diminished in chilling-stressed coriander plants. On the other hand, levels of ABA and soluble sugars were increased. Alleviation treatment by humic acid, followed by silicate and gamma irradiation, has notably promoted plant growth parameters and yield components in chilling-stressed coriander plants. This improvement was concomitant with a significant increase in phytohormones, photosynthetic pigments, carbohydrate contents, antioxidants defense system, and induction of large subunit of RuBisCO enzyme production. The assembly of Toc complex subunits was maintained, and even their expression was stimulated (especially Toc75 and Toc 34) upon alleviation of the chilling stress by applied biostimulators. Collectively, humic acid was the best the element to alleviate the adverse effects of chilling stress on growth and productivity of coriander. CONCLUSIONS: It could be suggested that the inducing effect of the pretreatments on hormonal balance triggered an increase in IAA + GA3/ABA hormonal ratio. This ratio could be linked and engaged with the protection of cellular metabolic activities from chilling injury against the whole plant life cycle. Therefore, it was speculated that seed priming in humic acid is a powerful technique that can benefit the chilled along with non-chilled plants and sustain the economic importance of coriander plant productivity.

Particle bombardment-mediated co-transformation of the Cht-2 gene in wheat and the associated changes in defense mechanisms in transgenic plants infected with Fusarium graminearum.

Fusarium graminearum is a major global pathogen of cereals and is considered the main causal agent of Fusarium head blight disease in wheat. Infection with Fusarium graminearum causes a significant reduction in crop yield and quality; therefore, it is very important to improve wheat pathogen resistance. In the present study, the plasmid pAHCht-2 harboring the rice chitinase (Cht-2) gene for pathogen resistance and the plasmid pAB6 containing the gus reporter and bar selectable marker genes were used for genetic transformation of immature embryo-derived calli of the Egyptian wheat cultivar Giza 164 using particle bombardment. Associated changes in defense mechanisms in the transgenic plants were investigated. The transgenic plants had significantly decreased total protein content, phenolic compounds and antioxidant enzyme activities (peroxidase and catalase), and significantly increased phenylalanine ammonia lyase and chitinase activities compared with non-transgenic plants under biotic stress conditions caused by F. graminearum infection. Our results show that activating a specific program of gene expression related to environmental stress conditions can reduce the cost of the stress on plant metabolism.