The Impact of Cell Wall Feruloylation on Plant Growth, Responses to Environmental Stress, Plant Pathogens and Cell Wall Degradability

Round 1

Reviewer 1 Report

This is a comprehensive review on the topic of plant cell wall feruloylation and its effects on cell expansion, plant growth, plant’s ability adapting to biotic and abiotic stresses, and tissue degradability. The authors covered many aspects related to cell wall ferulates and diferulates, ranging from structure to functions, focusing on current strategies used for manipulation of wall deruloylation. Overall, it’s a nice piece of work, although it’s worth further emphasizing in this manuscript that manipulating the formation of ferulates and diferulates in grasses may be an approach to achieve higher digestibility or increased yield of biomass fermentation. But among most of the practical cases, the cost of this approach is the reduced amounts of biomass and susceptibility to pathogens and abiotic stresses.

Some minor concerns:

1.     The labels or numbers above each scale bar in Figure 1 are too tiny. Suggest removing these numbers. In addition, after enlargement of Figure 1, the scale bar for a is ~250 mm, for b 200 mm, for c 500 mm, & for d 500 mm, which are different from what is describe in the figure legend.  

2.     The definition in line 224 “α-(1-3)-linked arabinose residues (AX)” is not correct. It is “α-arabinose 1 to 3 linked to backbone xylopyranose”.

3.     “ferulate-polysaccharide-lignin” in line 235 is better to be “polysaccharide-ferulate-lignin” complexes.

4.     There are two places needs to modify in Figure 2: 1). Does the bottom lignin interact with AX? If not, please move the lignin away from AX. 2). The bottom two chemical structures need to move away from each other, if they are not covalently linked to each other.

5.     It’s better to add note for what the “star” in Figure 3 means in the figure legend. In addition, the figure legend labeled 1, 2, 3 for the first three structures, while the last three structures were not labeled.

6.     Need to label the bottom panel in Figure 4, as the top two panels were labeled.

7.     From the sentence between 256 and 259, it seems like that the autofluorescence of the thin sections were generated because of ferulate dimers and tetramers. However, the figure legned of Figure 4 says “autofluorescence of cell wall phenolics”. It’s misleading in this way.

8.     Please give full names of “FAXX” in line 273 when it first appears.

9.     The terms for BAHD-acyl-transferases, BAHD acyl-CoA transferase, BAHD candidate genes, etc need to be consistent in the text of Section 2-i) Pathway genes.

10.  Is “3-dehydroshikimate dehydrate” in line 673 “3-dehydroshikimate dehydratase”?  

11.  The meanings of sentences between line 797 and 807 are confusing. The listed correlations are all negative, which need more consideration. Is the correlation between diferulates and resistance against herbivores and pathogens negative? It means that the higher diferulates and lower the resistance. Is the weevil susceptibility negatively correlated with total diferulate levels in maize? Is the resistance to Puccinia coronate negatively associated with lignin and less with ether ferulate levels?

Typos

1. Line 63 “cross-linked of pectin”: cross-linked pectin

2. Line 73 “role it pays in”: role it plays in

3. Line 87 “(PD)”: (DP)

4. Line 122 “ability of Gal residues”: ability of GalA residues

5. Line 941 “t3ied”: tried

Author Response

Please find reply to each point raised as attached word file

Author Response File: Author Response.docx

Reviewer 2 Report

I was asked to assess the manuscript “The impact of cell wall feruloylation on plant growth, responses to environmental stress, plant pathogens and cell wall degradability” authored by Buonafina and Morris. 

As the title implies, the presented review article aims to cover the influences of ferulic acid coupling in cell walls (of grasses) on different plant processes which is summarized under the heading “The role of cell wall feruloylation”. Beside that, a big part of the article deals with methods to manipulate feruloylation in order to get better understanding of the biosynthetic process and/or improve utilization properties.

Both authors are experts in the field and their conclusions and insights are well referenced. The review is nicely written and easy to understand for expert and non-expert readers. I have a few minor comments on that overall well-suited manuscript for publication in the journal “Agronomy”.

1.     The format of the headings is looking a bit weird to me. It seems to be not complying to the format of MDPI which uses numbered headings. Throughout the text, the authors also used different heading styles. I recommend to use the MDPI format as it is also easier to navigate in this review article because of high numbers of subheadings and sub-subheadings (especially after page 8).

2.     I recommend to carefully check for typos. There is one “PD” in line 87 which should be “DP”. “Maüle” should be “Mäule” in line 140. Additionally, “t3ied” should be “tried” in line 941.

3.     The introduction to the different cell wall components is nicely written. In case of hemicelluloses there could be added some information on general structure. The authors used the reference [25]. In that article, Scheller and Ulvskov proposed some structural features as common to the group of hemicelluloses. In case of pectins it is stated “there are four distinctive structural classes of polymers” (ll. 114+115) but five are mentioned after that. There is a classification into “HG”, “RG-I” and “substituted HG” by the group of Debra Mohnen. As only HG is discussed in greater detail in this manuscript, this could be an option to use.

4.     If my understanding is correct, Figures 1 and 4 are own original data. I wasn’t able to find any information in the author’s guidelines whether this is allowed in this journal. I know that the other big publisher from Switzerland explicitly states that review articles containing original data are not acceptable for publication and will be rejected. In this case the authors should think about the necessity to keep that data. If they decide to keep the figures, they should clearly indicate that they are unpublished original data.

5.     In Figure 3 there is no explanation of the “stars” in the Figure legend.

6.     Where is the reference for Figure 5? Is it published in Buonafina et al. (2020) [64]? This should be clearly stated in the figure legend.

7.     Throughout the text there are some inconsistencies regarding the abbreviations which should be revised, e.g. line 539 uses “Setaria viridis”, line 543 “Setaria viridis” and line 548 abbreviates “S. viridis”. In lines 584 and 593 the abbreviation “A.n. FAE” is used and afterwards “A. nidulans FAE” in line 608. Why is it not abbreviated after the first use? An abbreviation should be used after first use of the full name.

Overall, the article is a valuable source of information in a condensed form with expert perspective on the topic. I recommend publication of the manuscript after some minor revisions.

Best regards

Author Response

See attached document.

Author Response File: Author Response.docx