Diversity of CO2 Concentrating Mechanisms in Macroalgae Photosynthesis: A Case Study of Ulva sp.
, Chunyan Zhao 1,2,†, Shuang Zhao 1,3, Wei Dai 1, Jinlin Liu 1,4, Jianheng Zhang 1,5,*, Juntian Xu 5,6,* and Peimin He 1,5,7,*
Round 1
Reviewer 1 Report
No comments.
I would prefer if the review included an outline of methodology of CAs and CCMs assessments.
Very minor English language editing I realized.
Author Response
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Author Response.pdf
Reviewer 2 Report
This is a very well-done review on CCMs (and the processes, structures and functions related to) on Ulva sp. as a case study. The manuscript is well organized, using proper terminology in an easy-to-follow language. Still, I have some minor comments that need to be addressed:
L89-91. What about the studies by L. Axelsson, M. Björk, S. Beer on bicarbonate uptake in Ulva spp.? Did those studies not indicate the existence of CCMs in Ulva?
L105. Write the full name of the enzyme.
L62 and 325. Why to use “Enteromorpha” when now is an Ulva specie?
L188. The use of “thalli” is wrongly used here. The entire body of a macroalga is termed thallus (like Ulva). You probably are referring to the stipe?
There are several processes (CA activity and inhibitors, Rubisco functioning) explained in this review, so, it would be good to see more schematic figures representing them to make more visual this review.
Author Response
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Reviewer 3 Report
The authors try to give an overview of the CCM in Ulva species, and for the most part they have succeeded. Unfortunately some points are missing, especially the section on carbonate transporters, see for example Mallikarjuna et al (doi.org/10.1007/s12038-020-00080-z) or Santhanagopalan et al (doi.org/10.1093/jxb/erab169). Some points are generally unclear, for example the difference between Km (photosynthetic CO2) to Km (Rubisco CO2) (see below). If the errors are corrected, this manuscript can be a nice starting point for studying CCM in Ulva, covering most of the important literature. I would therefore recommend publication after revision. As a general point, images 1 and 2 are rather pretty, but completely redundant for the understanding of the content. more specific comments are below
Specific concerns:
54 not “the affinity of photosynthesis to inorganic carbon” is changed but the “availability of carbon for photosynthesis”
105 I was expecting a chapter on transporters, as stated in the paragraph starting on line 100. Why did you start with CA's?
120 CA is not a “transporter”
127 “it is catalyzed by cell wall or periplasmic CAs to convert into CO2”: These are two different points that need to be distinguished. Firstly, CAs, especially CAH1 in the periplasmatic area, convert CO2 to HCO3- and vice versa. It may function to maintain HCO3- for plasma membrane HCO3- transporters or CO2 for active CO2 uptake. Second, transport across the plasma membrane. Diffusion of CO2 and active transport of HCO3- by transporters (not by CAs).
135 2.2 and 2.3 belong together, discuss point iii) line 100 ff.
188-190 Acidification of the extracellular environment is in no way related to pyrenoids. This is misleading and should be removed.
211 please delete molecular
231 Algae are "among others" aquatic organisms
231-234 very long sentence with somehow redundant information “to adapt to the low CO2 environment in the water and maintain a high photosynthesis efficiency, most algae have evolved a CCM to ensure a supply of CO2 for photosynthesis”
244 “to compare the affinity of photosynthesis for external CO2 with the affinity of Rubisco for CO2” This is definitely not correct. See also comment on L54. Please revise this section (L242-256).
252 must read “can show its“
253 Km (photosynthetic CO2) to Km (Rubisco CO2) ???
260 must read „EZA (Ethoxzolamide)“
299 I don‘t see the point you want to adress in 3.4. Please revise this section.
316-323 Please revised this section. L316 an acquisition strategy means carbon uptake? L361 you mean options rather than “criteria” L317-319 Predicate is missing, revise sentence structure.
336 “absorption” should read “uptake”
340 “Ulva was involved in … the C3 pathway” please revise sentence
345 “use of CO2” is redundant (there is no plant that does not use CO2 for photosynthesis. Same for CA inhibitor. Either it is an Inhibitor of CA or not. If it is not tested, that’s no prove that it does not work.
359-363 long sentence, please revise. L361 what means “indirect mechanism”361 extracellular CA may always be involved. There is no connection to uptake of HCO3- or CO2 from the beginning of the sentence. What would you like to state here? 362 “inhibitory effect of CA inhibitors“ not necessarily as you stated above, there is a difference between EZA and AZA.
365 “the primary form of CA entry into the cell“ what would you like to say here? CA does not enter the cell.
367 Not important, since they never face low pH in nature.
370 “appear as inducible„ must read „appear to have inducible“
421 „Mechanism (i)“ means what? (and L428)
421 following the section starting from L384, it is confusing (and wrong) to write that Ulva always use the CO2 uptake option. Please revise.
436 section 4.2 is redundant since all mentioned facts have been discussed before in the manuscript
447 This section is very short. I would hope for more information here and possibly also conclusions for Ulva with regard to microalgae.
Especially the sentence structure and the use of verbs needs to be corrected in many places.
Author Response
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Author Response File: Author Response.pdf
