Correspondence/Rebuttal Cite This: J. Agric. Food Chem. XXXX, XXX, XXX−XXX
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Comment on mRNA-Sequencing Analysis Reveals Transcriptional Changes in Root of Maize Seedlings Treated with Two Increasing Concentrations of a New Biostimulant ABSTRACT: Overpopulation is already a reality, and the need for alternative technologies to meet a continuously increasing food demand has been much discussed around the world. In addition, soil decreasing fertility and desertification are obstacles that we will need to be overcome to increase crop productivity with a much-reduced dependence upon inorganic fertilizers. In this context, protein hydrolysates has emerged as an important strategy to reduce the use of inorganic fertilizers, whose applications as biostimulants for plant growth have shown very promising results.
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hydrolysates on root phenotype show significant values; however, there were no differences between doses. As for the alleged dose dependence of biomass increase, it was not altogether convincingly shown that the result was indeed dosedependent, as stated by the authors, because there were no statistical differences in the biomass increase of either roots or shoots in maize seedlings treated with doses A1 and A1/2. Nevertheless, the scientific contribution of this work, which has decisively shown important modifications in the transcriptome of maize seedlings grown under protein hydrolysate treatment, cannot be undermined. The study by Trevisan et al.3 substantiates the importance of protein hydrolysates with biofertilizer function. Although at first glance they may seem insignificant, the results on the increase of biomass under the effect of the different doses (A1 and A1/2) are in fact of the greatest consequence, because clearly, a very small dose of the protein hydrolysate is enough to stimulate corn growth and cause a great modification in transcriptome (29 553 expressed genes). The plant under treatment with half dose and whole concentration of protein hydrolyzate showed 290 and 643 differentially expressed genes, respectively, compared to corn not treated with the protein hydrolyzate. Thus, it is possible to visualize the biostimulating potential of protein-based products. Considering the strong biostimulating effect of protein hydrolysates on plant growth, this innovation in sustainable agriculture entails the opportunity to further discuss other works that have reported promising results in this field. The second commentary regarding this report is based on the comparison to other works on protein hydrolysates, mainly involving interesting results obtained with peptides derived from enzymatic hydrolysis. In general, the synthesis of peptide hydrolysates using peptidases has been an advantageous, ecologically safe strategy.4 The search for microbial peptidases5−10 is an advantageous pathway toward a diversified synthesis of peptides, because substrate specificity is peculiar to each proteolytic enzyme, which allows for each enzyme−substrate complex to yield different hydrolysates.7 In addition, the methodology involving proteolytic enzymes prevents damage to some essential amino acids and the release
n the 21st century, humanity faces unprecedented challenges that will put its courage and creativity to the test, to meet the demand for food supply by an ever-increasing world population.1 Overpopulation is already a reality, and the need for alternative technologies to meet a continuously increasing food demand has been much discussed in the context of sustainable agriculture. In addition, the predicted global temperature increase, drinking water scarcity, and soil decreasing fertility and desertification are obstacles that we will need to be overcome to increase crop productivity with a much-reduced dependence upon inorganic fertilizers.2 The proposition of sustainable agriculture based on the conscious management of natural resources and minimal damage to the environment by aggressive chemical agents has been wellaccepted by the entire scientific community and by the world population. As a promising strategy to reduce the use of inorganic fertilizers, protein hydrolysates have been tested as biostimulants for plant growth and have rendered results that compare quite well to conventional fertilizers. As a further effort to demonstrate the worth of protein hydrolysates as biostimulants for plant growth, Trevisan et al.3 reported a different profile of gene expression in maize after treatment with protein hydrolysate compared to that in the control treatment. Indeed, maize showed a larger set of transcribed genes under treatment with the biostimulant. In addition to the differences in the transcriptome, the authors showed phenotypic modifications of the plant, especially of the root, after hydrolysate treatment. This result confirmed the efficiency of protein hydrolysates as biostimulants for plant growth. In this commentary, the outstanding scientific contribution by the work of Trevisan et al.3 is duly acknowledged. However, an objective and useful evaluation of the worth of protein hydrolysates as biostimulants cannot ignore (1) some inconclusive results reported in this work, such as the occurrence of non-significant effects on maize growth (Figure 13) and the absence of any stimulating effect on leaves. In view of these unresolved issues, it is also important to analyze and compare (2) some promising results reported by other studies, in which hydrolysates produced by the enzymatic reaction are used, whose whole protein complement has been derived from residues little used by man, such as animal viscera and keratin. According to Figure 1,3 among the triplicates mentioned in each experiment, only the results pertaining to the effect of © XXXX American Chemical Society
Received: January 2, 2018 Published: February 14, 2018 A
DOI: 10.1021/acs.jafc.8b00022 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
Journal of Agricultural and Food Chemistry
Correspondence/Rebuttal
lignocellulolytic enzymes. Appl. Microbiol. Biotechnol. 2017, 101, 3089−3101. (7) da Silva, R. R.; de Oliveira, L. C. G.; Juliano, M. A.; Juliano, L.; Rosa, J. C.; Cabral, H. Activity of a peptidase secreted by Phanerochaete chrysosporium depends on lysine to subsite S′1. Int. J. Biol. Macromol. 2017, 94, 474−483. (8) da Silva, R. R.; de Oliveira, L. C. G.; Juliano, M. A.; Juliano, L.; de Oliveira, A. H. C.; Rosa, J. C.; Cabral, H. Biochemical and milkclotting properties and mapping of catalytic subsites of an extracellular aspartic peptidase from basidiomycete fungus Phanerochaete chrysosporium. Food Chem. 2017, 225, 45−54. (9) da Silva, R. R.; Souto, T. B.; de Oliveira, T. B.; de Oliveira, L. C. G.; Karcher, D.; Juliano, M. A.; Juliano, L.; de Oliveira, A. H. C.; Rodrigues, A.; Rosa, J. C.; Cabral, H. Evaluation of the catalytic specificity, biochemical properties, and milk clotting abilities of an aspartic peptidase from Rhizomucor miehei. J. Ind. Microbiol. Biotechnol. 2016, 43, 1059−1069. (10) da Silva, R.; Caetano, R.; Okamoto, D.; de Oliveira, L.; Bertolin, T.; Juliano, M. A.; Juliano, L.; de Oliveira, A. H.; Rosa, J.; Cabral, H. The Identification and Biochemical Properties of the Catalytic Specificity of a Serine Peptidase Secreted by Aspergillus f umigatus Fresenius. Protein Pept. Lett. 2014, 21, 663−671. (11) Ichida, J. M.; Krizova, L.; LeFevre, C. A.; Keener, H. M.; Elwell, D. L.; Burtt, E. H., Jr Bacterial inoculum enhances keratin degradation and biofilm formation in poultry compost. J. Microbiol. Methods 2001, 47, 199−208. (12) Gousterova, A.; Braikova, D.; Goshev, I.; Christov, P.; Tishinov, K.; Vasileva-Tonkova, E.; Haertle, T.; Nedkov, P. Degradation of keratin and collagen containing wastes by newly isolated thermoactinomycetes or by alkaline hydrolysis. Lett. Appl. Microbiol. 2005, 40, 335−340. (13) Santi, C.; Zamboni, A.; Varanini, Z.; Pandolfini, T. Growth Stimulatory Effects and Genome-Wide Transcriptional Changes Produced by Protein Hydrolysates in Maize Seedlings. Front. Plant Sci. 2017, 8, 433.
of toxic residues into the environment, as can occur when using chemical methods for obtaining protein hydrolysates. Ichida et al.11 and Gousterova et al.12 described the enzymatic hydrolysis of keratin and the consequent potential for the use of keratinous hydrolysates with biofertilizer action. Santi et al.13 also demonstrated the successful application of protein hydrolysate in maize cultivation, by a significant increase of biomass observed in roots and leaves. Colla et al.1 also demonstrated a remarkable increase of biomass in horticultural crop protein hydrolysate treatment. The highly positive effect of protein hydrolysates in agriculture has proven to be an attractive alternative to satisfy the increasing world food demand in a more sustainable way. The study by Trevisan et al.3 merits acceptance and recognition because of the results presented and for substantiating the successful application of protein hydrolysates as biostimulants in maize cultivation. This commentary has been to reflect on a subject in the field of sustainable agriculture that has gained increased attention in recent years. In doing so, we wish to strengthen scientific cooperation on subjects of great interest with regard to new technologies. The application of peptide hydrolysates to recover soil fertility and improve soil microbial activity and nutrient uptake by plant roots in place of inorganic fertilizers is a strategy on the rise. As with any new technology, more studies are needed to improve production techniques to ensure a lowcost product for consumption and a high use efficiency.
Ronivaldo Rodrigues da Silva*
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Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n Campus Universitário da USP, Ribeirão Preto, São Paulo 14040-903, Brazil
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Ronivaldo Rodrigues da Silva: 0000-0002-6504-8406 Notes
The author declares no competing financial interest.
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REFERENCES
(1) Colla, G.; Nardi, S.; Cardarelli, M.; Ertani, A.; Lucini, L.; Canaguier, R.; Rouphael, Y. Protein hydrolysates as biostimulants in horticulture. Sci. Hortic. 2015, 196, 28−38. (2) Food and Agriculture Organization of the United Nations (FAO). The Future of the Food and Agriculture: Trends and Challenges; FAO: Rome, Italy, 2017; http://www.fao.org/publications/fofa/en/ (accessed Jan 2, 2018). (3) Trevisan, S.; Manoli, A.; Ravazzolo, L.; Franceschi, C.; Quaggiotti, S. mRNA-Sequencing Analysis Reveals Transcriptional Changes in Root of Maize Seedlings Treated with Two Increasing Concentrations of a New Biostimulan. J. Agric. Food Chem. 2017, 65, 9956−9969. (4) da Silva, R. R. Bacterial and Fungal Proteolytic Enzymes: Production, Catalysis and Potential Applications. Appl. Biochem. Biotechnol. 2017, 183, 1−19. (5) da Silva, R. R.; Cabral, T. P. F.; Rodrigues, A.; Hamilton, C. Production and partial characterization of serine and metallo peptidases secreted by Aspergillus f umigatus Fresenius in submerged and solid state fermentation. Braz. J. Microbiol. 2013, 44, 235−243. (6) da Silva, R. R.; Pedezzi, R.; Souto, T. B. Exploring the bioprospecting and biotechnological potential of white-rot and anaerobic Neocallimastigomycota fungi: Peptidases, esterases, and B
DOI: 10.1021/acs.jafc.8b00022 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
