Grape Tartaric Acid: Chemistry, Function, Metabolism, and Regulation

Round 1

Reviewer 1 Report

The manuscript is an interesting review of the synthesis of tartaric acid (TA) in grapes and its relevance in grape and wine quality, biosynthetic routes, synthesis regulation as well as the influence of environmental factors, however some minor points must be addressed to improve the publication.

Line 42, please put the year.....According to Liu and Zhang....

Lines 70-72, L-(R,R)-(+)- Tartaric acid is dextrotartaric acid?, D-(S,S)-(-)-Tartaric acid is levotartaric acid?, is that right?

 In section 7 authors must include in perspetives the use of transcriptome and metabolome analysis to understand the regulation of TA in grapes, as well the use of gene editing to generate efficient grape varieties for TA synthesis versus climate warming

Author Response

Dear reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Grape tartaric acid: chemistry, function, metabolism and regulation”. Those comments are valuable and helpful for revising and improving our paper, as well as the important guiding significance to our research. We have considered all comments very carefully and made corrections to meet with approval. The manuscript was carefully revised based on editor. We also included a point-by-point response to the reviewers’ comments.

Looking forward hearing the updates.

Warmest regards,

Chun-Hua Ma

Author Response File: Author Response.pdf

Reviewer 2 Report

This article provides a review of tartaric acid accumulation and metabolism in grapevine. This topic was recently reviewed in detail elsewhere (Frontiers in Plant Science, 2021), and this should have been acknowledged more widely. It should also be pointed out that at least one sentence in the introduction – L51-52 was directly copied from the Frontiers review. Furthermore, Figure 2 looks to be adapted from the same review, without appropriate citation.

The novelty of this ms lies within the exploration of Asc metabolism in other plants, including transcriptional regulation of Asc biosynthesis genes, to inform future work on Asc and TA regulation in grape.  

The major concerns for this manuscript, are several places where findings from the literature have been misinterpreted. Examples are included throughout the detailed comments below. 

L37 (and other places) – winemaking is via fermentation, not brewing

L47-50 – a very long sentence. Should be divided into at least 2 sentences.

L89-92 – TA levels usually only decrease when considered as a concentration. When expressed as an amount per berry, TA levels generally remain stable during ripening.

L118-120 – does not make sense.

L203-304 – this comes out of nowhere, as there was no other mention of stress.

L201-211 – the location on Ch4 is irrelevant to the nomenclature VTC2. This sentence is unclear.

L268-274 – this sentence is too long and unclear. Also, the term enzyme pair is unclear, as only discussing one enzyme here. Perhaps referring to the two mutants described by Aboobucker et al.? Also, it would seem that Asc is limited by the supply of substrate for the enzyme, if L-GulL supply increases Asc synthesis (i.e. not limited by the enzyme as stated).

L282-284 –  contradictory. Increased or decreased with berry ripening? Also, Melino et al. suggested this enzyme is important during ripening while the Smirnoff-Wheeler pathway is important before ripening. This level of detail is missing here.

L286-288 – this statement is a misinterpretation. Expression of a gene during ripening does not mean it is related to colour change, and this idea was not proposed in the cited paper.

L312-316 – another very long sentence and could be clearer.

L333-334 – it is not the timing of expression that confirms the role of this enzyme, although it is important.

L341-342 – this is a misinterpretation. The “Class I” sorbitol dehydrogenase encoded by the Lidh2 gene likely does not participate in L-IDH activity at all, due to key differences in amino acid residues at the active site of the encoded protein. This is a main conclusion of Jia et al.

L343-345 – true, but another explanation for this in the Burbidge et al. review, which provides a more detailed description of this enzyme and should at least be cited.

L361 – not yet reported in plants….except in the Jia et al. (2019) paper? Again, reader could be referred to the Burbidge review for more detail on this enzyme.

 L395-397 -  The decrease in TA between 82-100 days is negligible. What evidence is there that TA salts are converted to other free acids? Also, it is not well established that TA content declines linearly in late stages of ripening. TA concentration may decline as an effect of dilution as the berries enlarge during ripening. But the amount of TA per berry typically does not decrease during ripening. This statement also conflicts with earlier statement (L384-386) that endogenous TA is not metabolised during ripening.

L412-416 – another long, unclear sentence.

L417-420 – this was not the conclusion of the cited paper.

L425-427 – misinterpretation: it wasn’t really an increase in TA, rather a delay in ripening. By harvest ripeness, the TA concentrations were comparable in the presence and absence of NAA treatment.

L427-434 – cannot say whether these statements are correct interpretations as I do not have access to the cited papers.

L439 – V. vinifera is not a tree

L441-443 – 'single stem and double arm' mentioned twice. Unclear sentence.

Figure 2 – no description of the regulators in the legend.

English language was mostly fine, except a few areas where sentences were too long and unclear, as given in the detailed comments. 

Author Response

Dear  reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Grape tartaric acid: chemistry, function, metabolism and regulation”. Those comments are valuable and helpful for revising and improving our paper, as well as the important guiding significance to our research. We have considered all comments very carefully and made corrections to meet with approval. The manuscript was carefully revised based on editor. We also included a point-by-point response to the reviewers’ comments.

Looking forward hearing the updates.

Warmest regards,

Chun-Hua Ma

Author Response File: Author Response.pdf

Reviewer 3 Report

The review “Grape tartaric acid: chemistry, function, metabolism and regulation” covers the most important points of the structure, the biosynthesis the catabolism of tartaric acid. It also deals with the effect exerted by temperature and light on TA faith in ripening berries. Catabolism and agronomic effects on TA accumulation are less detailed respect to the former part. I suggest to widen these two parts (points 5 and 6).

In the text there are serious language inaccuracies that render the text, the meaning of the text, difficult to understand or non-understandable at all.

Some examples:

Lines 28-30 rephrase, the sentence is incomprehensible.

Line 40; less susceptible … respect to??

Line 44 rancidity? What do you mean? It is odd that a wine can become rancid. Detail.

Line 58-63 is too long.

Lines 71 accumulates as rather than present is.

Lines 113-123: rephrase.

Lines 173-175 rephrase.

Lines 183-186 rephrase.

Line 193: Gulose and its derivatives are not novel anymore (cited publications date back to 2003 and 2009).

Lines 240-243 rephrase.

Lines 256-259: this is a general consideration that has already been expressed and it should be eliminated or integrated in Future perspectives.

Lines 268-272 rephrase.

Line 282-285: Non-comprehensible.

Line 301: eliminate during fruit ripening in kiwifruit (already clearly stated).

Line 335-336; rephrase.

Line 349: before? Later?

Lines 391-395; rephrase.

Line 440: substitute: shaping methods with training systems.

Line 446: there is a non-comprehensible symbol. What do you mean?

Line 455: what do you mean writing ‘yield in the leaves increased’?

Part 6.3 is correctly written and it goes smooth.  

English is to revise, deeply. 

Author Response

Dear  reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Grape tartaric acid: chemistry, function, metabolism and regulation”. Those comments are valuable and helpful for revising and improving our paper, as well as the important guiding significance to our research. We have considered all comments very carefully and made corrections to meet with approval. The manuscript was carefully revised based on editor. We also included a point-by-point response to the reviewers’ comments.

Looking forward hearing the updates.

Warmest regards,

Chun-Hua Ma

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have made changes to the text in line with comments from reviewers but many of the changes contain grammatical errors.

Line 24: change cytoplasm back to tonoplast.

L141: rearrange sentence. The acid must first be synthesised before it can accumulate in the vacuole.

Still grammatical errors throughout

Author Response

Dear editors and reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Grape tartaric acid: chemistry, function, metabolism and regulation”. Those comments are valuable and helpful for revising and improving our paper, as well as the important guiding significance to our research. We have carefully considered all comments and made revisions for approval. We have carefully revised the English grammatical errors in the manuscript based on the reviewers' comments.

Responses for Reviewer #2:

Comment 1: Line 24: change cytoplasm back to tonoplast

Response: Thanks for your suggestions and recognition. There's no cytoplasm on line 24，We changed the vacuolar transporter to tonoplast in line 118.

Comment 2: L141: rearrange sentence. The acid must first be synthesised before it can accumulate in the vacuole.

Response: Thanks for your suggestions and recognition. In the revised version, we have rearranged the sentences as follows:

“Therefore, distribution of TA is related to berry maturity. TA is mainly synthesized in the cytoplasm in immature berries, and in mature berries the accumulated TA is mainly stored in the vacuole.”

Looking forward hearing the updates.

Warmest regards,

Chun-Hua Ma

Reviewer 3 Report

The manuscript has improved but, still, there are some issues. 

See the attached file. 

Comments for author File: Comments.pdf

Many sentence are still to re-write. 

Author Response

Dear editors and reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Grape tartaric acid: chemistry, function, metabolism and regulation”. Those comments are valuable and helpful for revising and improving our paper, as well as the important guiding significance to our research. We have considered all comments very carefully and made corrections to meet with approval. The manuscript was carefully revised based on editor. We also carefully checked and responded to the new comments marked in red.

Responses for Reviewer #1:

Comment 1: Lines 28-30rephrase, the sentence-is incomprehensible. OK

Response: Thanks for your suggestions and recognition.

Comment 2: Line 40; less susceptible ... respect-to??OK

Response: Thanks for your suggestions and recognition.

Comment 3: Line 44 rancidity? What do you mean? It is odd that a wine can become rancid. Detail. Still to be detailed, what do you mean with rancidity in wines?

Response: Thanks for your suggestions. If the acetic acid content in wine is excessive, it is possible that the rancidity is caused by bacteria, and the acetic acid bacteria oxidize the alcohol into acetic acid in contact with the air. When the tartaric

acid content in the berry is high, the pH value of the juice is low. Under low pH, other

conditions remain constant, the fermented wine is relatively clear, and it is not easy to

be spoiled due to the action of microorganisms.

Comment 4: Line 58-63 is too long. OK

Lines 71 accumulates as rather than present is. OK

Response: Thanks for your suggestions and recognition.

Comment 5: Line 99: move ‘TA content measured in grams’ to line 97 after TA levels.

Response: Thanks for your suggestions. We have modified in the revision.

Comment 6: Lines 113-123: rephrase. OK, it is clearer but it could be improved.

Response: Thanks for your suggestions. We have modified the sentence in the revised version (see p3, line113-123).

Comment 7: Lines 162 and following: English is not correct.

Response: Thanks for your suggestions. We have fixed the syntax error in the revised version (see p4, line162-166).

Comment 8: Lines 173-175 rephrase. OK

Lines 183-186 rephrase. OK

Response: Thanks for your suggestions and recognition.

Comment 9: Lines 191-195: English is not correct = eliminate that

Response: Thanks for your suggestions. We have redrawn the sentence in the revised version (see p5, line191-195).

Comment 10: Lines 355 -360 rephrase, non-comprehensible.

Response: Special thanks to you for your good comments. We have rephrased the sentence in the revised version (see p8, line354-358).

Comment 11: Lines 389 – 394 rephrase, non-comprehensible.

Response: Thank you very much for your outstanding comments. We have rephrased the sentence in the revised version (see p9, line390-397).

Comment 11: Line 440: substitute: shaping methods with training systems. Add s to rootstocks.

Response: Thank you very much for your comments. We have Add s to rootstocks in the revised version.

Comment 12: Lines 433 -451: interesting points but sentences are not well written; rephrase.

Response: Thanks for your suggestions. We have rephrased the sentence in the revised version (see p21, line435-448).

Comment 13: Line 472: the word light is repeated twice. Nice information added.

Response: Thanks for your suggestions. The repeated light was removed.

Looking forward hearing the updates.

Warmest regards,

Chun-Hua Ma