Transcriptome-Wide Identification of Differentially Expressed Genes in Solanum lycopersicon L. in Response to an Alfalfa-Protein Hydrolysate Using Microarrays

Abstract

An alfalfa-based protein hydrolysate (EM) has been tested in tomato (Solanum lycopersicon L.) plants at two different concentrations (0.1 and 1 mL L-1) to get insight on its efficacy as biostimulant in this species and to unravel possible metabolic targets and molecular mechanisms that may shed light on its mode of action. EM was efficient in promoting the fresh biomass and content in chlorophyll and soluble sugars of tomato plants, especially when it was applied at the concentration of 1 mL L-1. This effect on plant productivity was likely related to the EM-dependent up-regulation of genes identified via microarray and involved in primary carbon and nitrogen metabolism, photosynthesis, nutrient uptake and developmental processes. EM also up-regulated a number of genes implied in the secondary metabolism that leads to the synthesis of compounds (phenols and terpenes) functioning in plant development and interaction with the environment. Concomitantly, phenol content was enhanced in EM-treated plants. Several new genes have been identified in tomato as potential targets of EM action, like those involved in detoxification processes from reactive oxygen species and xenobiotic (particularly glutathione/ascorbate cycle-related and ABC transporters), and defense against abiotic and biotic stress. The model hypothesized is that elicitors present in the EM formulation like auxins, phenolics, and amino acids, may trigger a signal transduction pathway via modulation of the intracellular levels of the hormones ethylene, jasmonic acid and abscissic acid, which then further prompt the activation of a cascade events requiring the presence and activity of many kinases and transcription factors to activate stress-related genes. The genes identified suggest these kinases and transcription factors as players involved in a complex crosstalk between biotic and abiotic stress signaling pathways. We conclude that EM acts as a biostimulant in tomato due to its capacity to stimulate plant productivity and up-regulate stress-related responses. Its use in agricultural practices may reduce the need of inorganic fertilizers and pesticides, thereby reducing the environmental impact of productive agriculture.

Metabolite-Targeted Analysis and Physiological Traits of Zea mays L. in Response to Application of a Leonardite-Humate and Lignosulfonate-Based Products for Their Evaluation as Potential Biostimulants

“…This observation seems to suggest that when plants are treated with Hs, two preferential metabolic pathways can be mainly stimulated, i.e., the N primary metabolism that produces proteins and the secondary metabolism involved in the synthesis of phenolics. These two metabolic pathways have been previously identified as principal targets of humic substances and other biostimulants, including lignosulfonate-humates, in maize and other plant species [17,49]. With respect to phenolic compounds, the increase in content of a number of them, especially in leaves, to levels that were not injurious to plants, can be deemed as an important result because these phytochemicals have recognized health beneficial properties, are implied in the plant defense responses against stress conditions, and mediate plant relationships with ecological partners [50][51][52][53].…”

Plant- and Seaweed-Based Extracts Increase Yield but Differentially Modulate Nutritional Quality of Greenhouse Spinach through Biostimulant Action

“…A presumed mechanism behind the plant-growth stimulation effect is the presence of signaling molecules such as small peptides which are typical components of the commercial PH Trainer ® used in the current experiment. The bioactive peptides in the Trainer ® formulation could act as elicitors since they are easily received by both leaf and root, thus may have triggered a signal transduction pathway through modulation of endogenous phytohormone biosynthesis (auxin-and/or gibberellin-like activities; [28,37]) thus boosting crop yield. Another putative mode of action behind the stimulation effect of legume-derived PH on fresh yield is the modulation of the root system architecture in particular the increase in root hair length and density [38], which may improve N use efficiency, thus boosting total fresh and dry biomasses.…”

“…The higher SPAD index values observed in spinach plants treated with biostimulants (PH, SWE or VO + SWE) could be also considered a mechanism by which biostimulant application can promote N uptake efficiency. In fact, SPAD index is widely considered as a key indicator of chlorophyll biosynthesis and photosynthetic apparatus functioning, that contributed to the translocation of photosynthates (i.e., soluble sugars) via the phloem from sources to the sinks, thus boosting crop performance [2,37]. Table 2.…”

“…The ability of PH containing free amino acids and peptides to avoid accumulation of nitrates in leaf tissue could be associated to an up-regulation of the key nitrogen assimilation genes like nitrate reductase, thus contributing to a higher assimilation of nitrates into amino acids [49]. soluble peptides [2,16]; (ii) the greater uptake, translocation and accumulation of nutrients effecting stimulation of the root system architecture [18,28]; and (iii) the expression of genes encoding for macronutrients transporters in cell membranes [37,47]. From a botanical point of view, spinach, which belongs to the Chenopodiaceae family, is normally considered a nitrate-accumulating leafy vegetable species [48].…”

Leaf Development Monitoring and Early Detection of Water Deficiency by Low Field Nuclear Magnetic Resonance Relaxation in Nicotiana tabacum Plants

“…Using biostimulants makes it possible to reduce the amount of fertilizer thereby reducing the negative impact of the crop on the environment. The use of biostimulants to prevent abiotic stress is less documented, but several studies have highlighted changes in the expression of genes involved in the abiotic stress resistance [18][19][20].…”