Heat Shock Treatment Promoted Callus Formation on Postharvest Sweet Potato by Adjusting Active Oxygen and Phenylpropanoid Metabolism

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

Question1: Keywords: these words are usually different from the ones that appear in the title.

Response: Thanks for your valuable suggestions. We have modified the keywords as required to ensure that the modified keywords are different from the title. The modified part has been marked in red font. (Page 1, Line32-33)

 

Question2: Introduction: The pre-harvest treatment of the potatoes is very important for a better response to a postharvest treatment, so it is interesting to provide information on the crop. More details should be given about this topic.

Response: Thanks for your valuable suggestions. Indeed, we found there were some studies of potatoes and other crops pointed out that the multiple fungicide stroby sprays treatment and sodium nitroprusside treatment during preharvest process could promote the wound healing for postharvested potatoes. We have supplemented the references on the effects of preharvest treatment on some postharvest crops storage. The supplement has been marked in red. (Page 2, Line66-70)

 

Question3: Materials and methods

I believe that sampling should also have been done at 7 and 15 days more later, as potatoes are a product that is stored for a long time before being sold.

Response: Thanks for your valuable suggestions. It is inevitable that sweet potato will be damaged by external machinery during harvest, so it must be callused in a short time to resist microbial infection and water loss. Therefore, in this study, RHT technology was used as a short stimulation treatment to promote healing and then stored for 5 days to complete the callus process. The objective is to explore how RHT heat treatment can promote the rapid formation of wound callus by stimulation in a short time.

 

Question4: Other points, for future experiments, it is important to control the pre-harvest factors that have affected the potatoes in the sample.

Response: Thanks to the reviewers for their valuable suggestions, which are precise. We are conducting some research on preharvest factors affecting the postharvest storage effect of sweet potatoes, such as the effect of different preharvest water-fertilizer application methods on the storage quality and callus effect of sweet potatoes. This is also one research part of the funding that supports this research.

 

问题5： 另一个有趣的方面是，感官质量分析是必要的，以关联消费者对这些保存技术的接受程度，并观察愈伤组织形成是否会影响干扰味道的特性，从而影响消费者的接受度。

响应： 感谢审稿人的宝贵建议。确实缺乏相关研究来验证甘薯或马铃薯的愈伤组织形成是否影响可食用特性。然而，由于这次修订的时间非常短，可能无法补充感觉测试数据。如果审稿人和编辑认为有必要在本次修订的返回中加入感官评价数据，我们下次会补充数据。

 

问题6：数据统计与分析

至于统计数据，我认为将主要影响：时间和温度以及它们的相互作用也是正确的。

响应： 感谢您的宝贵建议。处理时间和温度是影响甘薯愈伤组织愈合的主要因素，但数据分析的目的是通过相关性分析，探索苯丙烷代谢与活性氧代谢之间的关键相关产物和酶的相关性。因此，我们没有将温度和时间考虑在相关性分析中。

 

问题7：否则，在我看来，这是一篇结构良好的文章，其相关结果有助于改善马铃薯的运输和储存，同时对环境和消费者都有不那么激进和可持续的方法。

响应： 再次感谢审稿人对我们研究的肯定，我们将根据您的建议详细修改文章。

Author Response File: Author Response.doc

Reviewer 2 Report

Comments to the Author: 

The research article “Heat shock treatment promoted callus formation on postharvest sweet potato by adjusting active oxygen and phenylpro- 3 panoid metabolism” by Q. Xin et al.  is a well compiled study and presented satisfactorily. I feel it does suffice and fall within the publishing criteria and scope of journal. However in the present form there are certain minor issues and clarifications which should be addressed before final acceptance. The comments are mentioned below:

1.      “Figure 2A shows that from day 1, the lignin content 104 in the sweet potato had significantly increased compared with the raw samples under 105 RHT and CK. Thus, there may be no correlation between lignin metabolism and high temperature stimulation in sweet potato” (Page3: Line 104-103)######

Author should give explanation to this and /or mention the reason behind.???

2.      Figs. 1 and 2A reveal that callus thickness was greatest under RHT at 65 °C. (Page 3: Line 110-111)########

Author should explain why?

 

3.      By contrast, the total phenol and flavonoid levels did not differ between sweet potatoes treated with RHT at 50 °C and those treated with RHT at 80 °C. (Page4: Line 127-128).#######

 

If there is any effect of temperature on structure/stability of such compounds? authors should draw the structure of some important compounds related to the crucial results highlighted in the paper.

4.      Furthermore, the accumulation of phenolic compounds may help sweet potato wounds rapidly heal and form callus tissue. (Page4-5: Line 146-147).#######

How accumulation of phenolic compounds heal wounds on sweet potato. Any mechanism? The mention in brief. Authors may give reference of any established mechanism highlighted therein.

 

5.      RHT treatment stimulated phenylpropanoid metabolism in sweet potato possibly because active oxygen metabolism occurred in the wounds (Page6-7: Line 193-194). #########

Explain or mention the reference herein? Any evidence in published reports??

 

6.      Pearson’s correlation analysis was conducted (Page8: Line 230). #########

mention the reference herein?

 

7.      The absorbance was measured at 280 nm. ######################

Why absorbance was measured at 280 nm (Page12: Line 383).

 

8.      The results of this study may provide theoretical and methodological bases for rapid callus induction in postharvest sweet potato. (Page13: Line 466). #############

What do authors mean by theoretical bases for………….

9.      Provide a possible mechanism of action in flow chart.

Author Response

To Referee

Question1：“Figure 2A shows that from day 1, the lignin content 104 in the sweet potato had significantly increased compared with the raw samples under 105 RHT and CK. Thus, there may be no correlation between lignin metabolism and high temperature stimulation in sweet potato” (Page3: Line 104-103)

Author should give explanation to this and /or mention the reason behind.???

Response: Thanks for the valuable suggestions. Here are the writing mistakes. In order to avoid reading ambiguity, this sentence has been deleted in the revised manuscript.. (Page 3, Line105-106)

 

Question2：Fig. 1 and 2A reveal that callus thickness was greatest under RHT at 65 °C. (Page 3: Line 110-111) Author should explain why?

Response: Thanks for the valuable suggestions. This may be due to the lack of understanding of the callus mechanism here. The callus is composed of cross-linked stacks of lignin and polyphenol suberin. The higher the amount of the two substances produced, the thicker the callus. Therefore, by measuring the lignin content (Fig. 1) and combining with the suberin deposition thickness (Fig. 2A), it can be judged that within 65 °C RHT the callus thickness is the largest. We have added a discussion of the callus mechanism here (Page 3, Line110-115). A flow chart (Fig. 7) of sweet potato callus mechanism has been added, which has been marked in red.

 

Question3：By contrast, the total phenol and flavonoid levels did not differ between sweet potatoes treated with RHT at 50 °C and those treated with RHT at 80 °C. (Page4: Line 127-128). If there is any effect of temperature on structure/stability of such compounds? authors should draw the structure of some important compounds related to the crucial results highlighted in the paper.

Response: Thanks for the valuable suggestions of reviewers. First, the content of the key phenolics was less in harvested raw sweet potato before heat treatment. Therefore, the effect of temperature on the stability of polyphenols and flavonoids in sweet potato under RHT treatment was low and could be almost ignored. Secondly, as a method of callus promoting, RHT treatment mainly stimulates the reactive oxygen species and phenylpropane metabolic pathways of sweet potato, thereby producing a large amount of polyphenols and flavonoids, and synthesizing cork layer to resist stress. In addition, we have added the chemical structural formulas of four polyphenolic compounds in Fig. 3. (Page 6, Fig. 3)

 

Question4：Furthermore, the accumulation of phenolic compounds may help sweet potato wounds rapidly heal and form callus tissue. (Page4-5: Line 146-147).

How accumulation of phenolic compounds heal wounds on sweet potato. Any mechanism? The mention in brief. Authors may give reference of any established mechanism highlighted therein.

Response: Thanks for the valuable suggestions of reviewers. Phenylpropane, fatty acid and reactive oxygen species metabolism are key pathways for the formation of sweet potato callus. Under thermal stimulation, reactive oxygen species metabolism is activated. Then a large number of phenolic compounds induced by phenylpropane metabolism are catalyzed to synthesize polyphenolic suberin. In addition, monophenolic compounds can form a large number of lignin monomers. The continuous stacking of polyphenol suberin and lignin is the cause of callus. An explanation of this mechanism is described in Discussion Part.

 

Question5：RHT treatment stimulated phenylpropanoid metabolism in sweet potato possibly because active oxygen metabolism occurred in the wounds (Page6-7: Line 193-194).

Explain or mention the reference herein? Any evidence in published reports?

Response: Thanks for the valuable suggestions. We have added references here, which discuss the mechanism of the association between reactive oxygen species metabolism and phenylpropane metabolism during sweet potato callus, that is, products such as superoxide anions of reactive oxygen species metabolism can promote the progress of phenylpropane metabolism. Modified parts were marked in red font. (Page 6, Line 194-196)

 

Question6：Pearson’s correlation analysis was conducted (Page8: Line 230).

mention the reference herein?

Response: Thanks for the valuable suggestions. In this study, Pearson's correlation analysis was used to analyze the key enzymes and key substances in sweet potato callus formation. Hence, this is the highlight of this paper that is different from other related studies to find out the key factors how RHT promotes sweet potato callus. In addition, we have added some discussion and references to the Results section of Pearson's correlation analysis. We also added a flow chart (Page 11, Fig. 7) of the mechanism of RHT treatment promoting callus formation in sweet potato. The newly added parts were marked in red font. (Page 8, Line 244-250)

 

Question7：The absorbance was measured at 280 nm.

Why absorbance was measured at 280 nm (Page12: Line 383).

Response: Thanks for the valuable suggestions. This section has been fixed in the Methods 4.3 due to a composing error. Revised parts were marked in red font. (Page 12, Line 379)

 

Question8：The results of this study may provide theoretical and methodological bases for rapid callus induction in postharvest sweet potato. (Page13: Line 466).

What do authors mean by theoretical bases for.

Response: Thanks for the valuable suggestions. This question is similar to question 5. Previous studies on the mechanism of sweet potato callus generally discussed the mechanism of phenylpropane metabolism, but did not deeply explore the relationship between reactive oxygen species metabolism and phenylpropane metabolism. In this experiment, by measuring the products and enzyme activities of the two metabolic pathways in the process of sweet potato callus, and conducting correlation analysis, the mechanism of action of the two parts and the key products were discussed. Therefore, it can provide a certain theoretical basis for subsequent in-depth exploration. We have also added the RHT treatment to promote sweet potato callus flow chart in the Discussion section (Page 11, Fig. 7)

 

Question9：Provide a possible mechanism of action in flow chart.

Response: Thanks for the valuable suggestions. We have added a flow chart on the mechanism of RHT treatment promoting sweet potato callus in the Discussion section. (Page 11, Fig. 7)

Author Response File: Author Response.doc