Inhibitory Effect of L-Methionine on Alternaria alternata Based on Metabolomics Analysis
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis study explores the antifungal properties of methionine (Met) against Alternaria alternata, the primary pathogenic fungi causing postharvest black spot/brown spot in fruits and vegetables. Through in vitro assays and metabolomics analysis, the research reveals that Met treatment concentration-dependently inhibits A. alternata, affecting mycelium growth, spore germination, and germ tube elongation. Notably, Met's inhibitory effects diminish beyond a concentration of 50 mmolL-1.
Met treatment damages the plasma membrane integrity of A. alternata spores, leading to irreversible mycelium deformation. Additionally, it induces significant electrolyte, nucleic acid, and protein leakage from A. alternata cells, indicating heightened cell membrane permeability.
Metabolomics analysis identifies 81 different metabolites, categorizing them into seven groups, with implications for amino acid synthesis and metabolism, the pentose phosphate pathway, and the TCA cycle. The primary antifungal effect of Met disrupts cell membrane integrity, causing nucleic acid and protein leakage. This disruption further impacts vital metabolic pathways, including the TCA cycle, carbohydrate metabolism, and amino acid synthesis.
In conclusion, this study enhances our understanding of the antifungal mechanism of Met treatment on A. alternata, offering valuable insights for applying Met in preventing and treating postharvest black/brown spot in fruits and vegetables. The paper is concise and well written. In attachment my comments to improve the quality of the paper.
Comments for author File: 
Comments.pdf
Author Response
We very much appreciate the careful reading of our manuscript and valuable suggestions of the reviewer. We have carefully considered the comments and have revised the manuscript accordingly. The comments can be summarized as follows:
Introduction:
Page 1 Line 35: adaptability
“adaptabilit” has replaced “adaptability”.
Page 1 Line 35: For all the references mentioned in the text, please leave a space before the citation.
A space has been left before the citation.
Page 1 Line 40: Please add more references.
References have been added.
Page 1 Line 43: add references.
References have been added.
Materials and Methods
Page 2 Line 80-81: Add the manufacturer and the location. Example: (PDA; Oxoid Ltd., Basingstoke, UK)
“PDA” has replaced “PDA, Qingdao Hope Bio-Technology Co., Ltd, Qingdao, China”
Page 2 Line 88-89: Replace it with Ji et al., [15]
“The effects of Met on the mycelial growth of A. alternata were evaluated according to the methods previously reported [15]” has replaced “The effects of Met on the mycelial growth of A. alternata were evaluated according to the methods previously reported by Ji, et al [21]”.
Page 2 Line 91: add space after 0; the same of the previous comment
“90mm” has replaced “90 mm”.
“12mm” has replaced “12 mm”.
Page 3 Line 128-129: in room temperature? add please
“It was incubated in the dark for 20 min” has replaced “It was incubated at room temperature in the dark for 20 min”.
Results
Page 4 Line165: no in italics.If a subchapter is written in italics, the Latin name of the pathogen should not be in italics. Conversely, if the subchapter is written in regular font, the name of the pathogen should be in italics.
Page 4 Line165, Page5 L187, Page 6 Line206, Page 7 Line222: “A.alternata” has replaced “A.alternata”.
Page 5 Line 182: Can you please improve the image quality? It appears blurry.
The new picture has been replaced.
Page 9 Line 269-270: Can you please improve the image quality?
The new pictures have been replaced.
Reviewer 2 Report
The manuscript discusses studies that delve into the diverse facets of methionine's antifungal effects on Alternaria alternata. The conducted research encompasses an examination of the amino acid's impact on mycelial morphology, fungus growth rate, spore germination, plasma membrane integrity, electrolyte leakage, and metabolomics analysis of A. alternata following methionine treatment. This is a multifaceted study with practical implications, suggesting the potential utilization of methionine in safeguarding plants during the post-harvest phase.
My minor notes are as follows:
It is worth emphasizing in the title that the subject of the research was L methionine
The abbreviation MET was used in the abstract and expanded in the introduction. It may be worth including this information in the summary, even though MET is the standard abbreviation for methionine.
Although MET seems to be a good alternative in plant protection, it may be worth mentioning the side effects that this compound may cause in humans.
I think that the descriptions of the posted photos can be supplemented with at least the magnification used, and the photos themselves with a scale used to mark the size of the photo
no comments
Author Response
Thanks for your comments on our paper. We had revised our paper according to your comments. The comments can be summarized as follows:
Comments 1: It is worth emphasizing in the title that the subject of the research was L methionine.
Page 1 Line 2-3: “Inhibitory effect of methionine on Alternaria alternata based on Metabolomics analysis” has replaced “Inhibitory effect of L-methionine on Alternaria alternata based on Metabolomics analysis”.
Comments 2: The abbreviation MET was used in the abstract and expanded in the introduction. It may be worth including this information in the summary, even though MET is the standard abbreviation for methionine.
Page 1 Line 12: “Met” has replaced “L-methionine (Met)”
Comments 3: Although MET seems to be a good alternative in plant protection, it may be worth mentioning the side effects that this compound may cause in humans.
Page 2 Line 53-57: According to FDA (https://www.accessdata.fda.gov; CITE: 21CFR172.372; Title 21, Volume 3, accessed on 22 August 2022), methionine is one of nine essential amino acids in humans, and it could be safely added to food except for infant foods.Besides being a building block of proteins, L-methionine has also been revealed to regulate metabolic processes, immunity, and enteric function in mammals, as well as to intervene in endogenous antioxidant enzyme activation, lipid metabolism, and glutathione synthesis for counteracting oxidative stress. The effects of methionine on the human body were supplemented.
Comments 4: I think that the descriptions of the posted photos can be supplemented with at least the magnification used, and the photos themselves with a scale used to mark the size of the photo.
Page 6 Line 202: The magnification under the microscope has been supplemented. (40×10).
Page 7 Line 220-221: The magnification under microscopes and scanning electron microscopes has been supplemented. (40×10) (4000×).
