Abstract
Chitosan plays an important role in regulating growth and eliciting defense in many plant species. However, the exact metabolic response of plants to chitosan is still not clear. The present study performed an integrative analysis of metabolite profiles in chitosan-treated wheat seedlings and further investigated the response of enzyme activities and transcript expression related to the primary carbon (C) and nitrogen (N) metabolism. Metabolite profiling revealed that chitosan could induce significant difference of organic acids, sugars and amino acids in leaves of wheat seedlings. A higher accumulation of sucrose content was observed after chitosan treatment, accompanied by an increase in sucrose phosphate synthase (SPS) and fructose 1, 6-2 phosphatase (FBPase) activities as well as an up-regulation of relative expression level. Several metabolites associated with tricarboxylic acid (TCA) cycle, including oxaloacetate and malate, were also improved along with an elevation of phosphoenolpyruvate carboxylase (PEPC) and pyruvate dehydrogenase (PDH) activities. On the other hand, chitosan could also enhance the N reduction and N assimilation. Glutamate, aspartate and some other amino acids were higher in chitosan-treated plants, accompanied by the activation of key enzymes of N reduction and glutamine synthetase/glutamate synthase (GS/GOGAT) cycle. Together, these results suggested a pleiotropic modulation of carbon and nitrogen metabolism in wheat seedlings induced by chitosan and provided a significant insight into the metabolic mechanism of plants in response to chitosan for the first time, and it would give a basic guidance for the future application of chitosan in agriculture.
Highlights
Conventional crop production is increasingly being challenged by various problems such as decreased soil fertility and pollution due to the use of hazardous chemical pesticides and fertilizers at a global scale (Vassilev et al, 2015)
Obvious separations were found in groups of CK-(GlcN)6, CK-(GlcN)7, and CK-(GlcN)8, indicating that the orthogonal to partial least squares discriminant analysis (OPLS-DA) model can be used to identify the difference between the CK and chitosan-treated groups
It has been reported that chitosan could bind to many kinds of cell membranes including tobacco, strawberry, and oilseed rape cell and its binding specificity depended on the size of chitosan fragments (Guo et al, 2009; Yin et al, 2013, 2016)
Summary
Conventional crop production is increasingly being challenged by various problems such as decreased soil fertility and pollution due to the use of hazardous chemical pesticides and fertilizers at a global scale (Vassilev et al, 2015). There are few reports about the metabolic response mechanism of plant to chitosan It has attracted wide interests in understanding the mechanisms of chitosan-induced growth-promoting effect, which will provide a considerable agronomic benefit for future large-scale application of chitosan in crop production. An integrative analysis of metabolite profiling, transcripts and enzyme activities is necessary to understand the comprehensive response mechanisms of plants, which will provide much more actual information about the metabolic pathways involved. To investigate the chitosan-triggered metabolic responses mechanism in wheat seedlings, three chitosan oligosaccharides, including (GlcN), (GlcN), and (GlcN), were applied which were reported more effective in promoting plant growth by Zhang et al (2016). The metabolic responses of wheat seedlings to chitosan, including photosynthetic carbon metabolism, glycolysis, TCA cycle and central N metabolism, were further investigated at transcripts and enzyme activities levels. This article provided a comprehensive study on the metabolic regulation mechanism of chitosan on plants for the first time, and it would give a basic guidance for the future application of chitosan in agriculture
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