AtABCG14: A Long-Distance Root-to-Shoot Carrier of Cytokinin
Round 1
Reviewer 1 Report
In this short manuscript of communication from Kaur and Mishra, the authors summarized a paper published on the Plant Physiology by Zhao et al in April 2021 that AtABCG14 functions in unloading and distribution of root-synthesized cytokinin in phloem and its effect on shoot phenotype in Arabidopsis.
However, this manuscript seemed not so timely as it is at least more than one year since Zhao’s paper published, which is a lone time that many progress can be made in plant research area. Moreover, the title of this manuscripts, ‘AtABCG14: a long-distance root to shoot carrier of cytokinin’, is not appropriate for the story that Zhao’s paper told. Zhao et al found that atABCG14 played an important role in phloem unloading and distributing cytokinin synthesized in root through the apoplastic pathway in shoot. atABCG14 worked more like an unloader rather than a long-distance carrier in Zhao’ story. Besides, some of the writing is not clear in the manuscript. Here are some additional comments:
1. Line 38: what is “enhanced AtABCG14”? Did the authors mean ‘enhanced expression of AtABCG14?
2. Line 58: ‘14C’ should be ‘14C’; 2H5 should be “2H5”.
3. The experiments such as split-root assay to demonstrate the retrograde transport of root-synthesized tZ-type cytokinins to the roots are important to understand the function of atABCG14 and the phenotype of reciprocal grafting between WT and mutant. However, it was not touched in this manuscript except that in the figure 1 legend. Please add this section to the manuscript.
4. Line 61: what is ‘tZ expression’? tZ-type cytokinins is mainly synthesized in the roots and transfer to shoot. Did authors mean tZ distribution or delivery?
5. Figure 1: What does the blue rectangle in the shoot panel stand for?
6. Line 114: There is no need to show what are ‘PCC’ and ‘PC’. ‘PCC’ and ‘PC’ cannot be found in the image.
Author Response
- Line 38: what is “enhanced AtABCG14”? Did the authors mean ‘enhanced expression of AtABCG14?
Corrected; enhanced AtABCG14 -> ‘enhanced expression of AtABCG14
- Line 58: ‘14C’ should be ‘14C’; 2H5 should be “2H5”.
Corrected ‘14C -> 14C’ and ‘2H5 -> 2H5’
- The experiments such as split-root assay to demonstrate the retrograde transport of root-synthesized tZ-type cytokinins to the roots are important to understand the function of atABCG14 and the phenotype of reciprocal grafting between WT and mutant. However, it was not touched in this manuscript except that in the figure 1 legend. Please add this section to the manuscript.
It is now added from line 66- 70.
- Line 61: what is ‘tZ expression’? tZ-type cytokinins is mainly synthesized in the roots and transfer to shoot. Did authors mean tZ distribution or delivery?
Corrected “expression -> delivery”
- Figure 1: What does the blue rectangle in the shoot panel stand for?
It shows that the phloem companion cell mentioned in the figure legend.
- Line 114: There is no need to show what are ‘PCC’ and ‘PC’. ‘PCC’ and ‘PC’ cannot be found in the image.
Corrected by removing from line 114 “PCC, Pholem companion cells; PC, pericycle cells
Reviewer 2 Report
The subject of this research is very interesting and important for plant biology. Being attached to the substrate, plants must be able to adjust the growth of shoots and roots to changing environmental conditions. Transport of root- synthesized cytokinins to shoots via xylem is one of the means of "communication" due to which the shoot receives information about the root environment.
In my opinion this communication is worth it to be published, but after some edits.
1) In the abstract you write “In present study it has been identified that AtABCG14 protein mediates phloem unloading of cytokinins through the apoplastic pathway” (Lines 11, 12). However almost the same postulate we can find in the paper Zhao et al., 2021 which you cite. It seems to me that it is better to write that in your research you confirmed the participation of the transporter in the phloem unloading and in the cytokinin distribution in the shoot. For example, you can use the words “It has been proved…” instead of “It has been identified…”
2) When discussing the results, nothing is mentioned about other possible cytokinin transporters. For example, you write: “Reduction in diameter of rosette leaves, number of siliques, shoot apical meristem activity was also observed in the order of atabcg14/atabcg14 > atabcg14/WT > WT/atabcg14, compared to WT/WT.” (Lines 43-46). A reduction in the growth of the aerial part of plant in atabcg14/WT occurred to a lesser extent comparing with atabcg14/atabcg14. Does this mean that other cytokinin carriers may be involved in phloem unloading? And does this mean that the distribution of root-derived cytokinins in the shoot can occur without the participation of hormone translocation into the phloem and its subsequent unloading?
3) Could you take a look at the beginning of the Abstract (Line 7)? There are missing space and extra bold font.
Comments for author File: 
Comments.docx
Author Response
1) In the abstract you write “In present study it has been identified that AtABCG14 protein mediates phloem unloading of cytokinins through the apoplastic pathway” (Lines 11, 12). However almost the same postulate we can find in the paper Zhao et al., 2021 which you cite. It seems to me that it is better to write that in your research you confirmed the participation of the transporter in the phloem unloading and in the cytokinin distribution in the shoot. For example, you can use the words “It has been proved…” instead of “It has been identified…”
Corrected
2) When discussing the results, nothing is mentioned about other possible cytokinin transporters. For example, you write: “Reduction in diameter of rosette leaves, number of siliques, shoot apical meristem activity was also observed in the order of atabcg14/atabcg14 > atabcg14/WT > WT/atabcg14, compared to WT/WT.” (Lines 43-46). A reduction in the growth of the aerial part of plant in atabcg14/WT occurred to a lesser extent comparing with atabcg14/atabcg14. Does this mean that other cytokinin carriers may be involved in phloem unloading? And does this mean that the distribution of root-derived cytokinins in the shoot can occur without the participation of hormone translocation into the phloem and its subsequent unloading?
Added to line 47-52
3) Could you take a look at the beginning of the Abstract (Line 7)? There are missing space and extra bold font.
Corrected
