Abstract
Background and Aims: In some plant families, including Cucurbitaceae, initiation and development of lateral roots (LRs) occur in the parental root apical meristem. The objective of this study was to identify the general mechanisms underlying LR initiation (LRI). Therefore, the first cellular events leading to LRI as well as the role of auxin in this process were studied in the Cucurbita pepo root apical meristem. Methods: Transgenic hairy roots harbouring the auxin-responsive promoter DR5 fused to different reporter genes were used for visualizing of cellular auxin response maxima (ARMs) via confocal laser scanning microscopy and 3-D imaging. The effects of exogenous auxin and auxin transport inhibitors on root branching were analysed. Key Results: The earliest LRI event involved a group of symmetric anticlinal divisions in pericycle cell files at a distance of 250-350 µm from the initial cells. The visualization of the ARMs enabled the precise detection of cells involved in determining the site of LR primordium formation. A local ARM appeared in sister cells of the pericycle and endodermis files before the first division. Cortical cells contributed to LR development after the anticlinal divisions in the pericycle via the formation of an ARM. Exogenous auxins did not increase the total number of LRs and did not affect the LRI index. Although exogenous auxin transport inhibitors acted in different ways, they all reduced the number of LRs formed. Conclusions: Literature data, as well as results obtained in this study, suggest that the formation of a local ARM before the first anticlinal formative divisions is the common mechanism underlying LRI in flowering plants. We propose that the mechanisms of the regulation of root branching are independent of the position of the LRI site relative to the parental root tip.
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Claims 8
Claim · model-written summary
The earliest lateral root initiation event was symmetric anticlinal divisions in pericycle cell files 250-350 µm from the initial cells.
- Taxon
- Cucurbita pepo
Cucurbita pepot0 - Organ / stage
- pericycle cell filese0
- Outcome
- symmetric anticlinal divisions in pericycle cell filese0
- Value
- 250-350 µme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cucurbita pepo”
e0“The earliest LRI event involved a group of symmetric anticlinal divisions in pericycle cell files at a distance of 250-350 µm from the initial cells”
Claim · model-written summary
A local auxin response maximum appeared in sister cells of pericycle and endodermis files before the first division.
- Taxon
- Cucurbita pepoCucurbita pepot0
- Organ / stage
- sister cells of the pericycle and endodermis filese1
- Outcome
- local ARMe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cucurbita pepo”
e1“A local ARM appeared in sister cells of the pericycle and endodermis files before the first division”
Claim · model-written summary
Cortical cells contributed to lateral root development via an auxin response maximum formed after pericycle anticlinal divisions.
- Taxon
- Cucurbita pepoCucurbita pepot0
- Organ / stage
- Cortical cellse2
- Outcome
- contributed to LR developmente2
- Qualifier
- formation of an ARMe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cucurbita pepo”
e2“Cortical cells contributed to LR development after the anticlinal divisions in the pericycle via the formation of an ARM”
Claim · model-written summary
Exogenous auxins did not increase the total number of lateral roots.
- Taxon
- Cucurbita pepoCucurbita pepot0
- Treatment
- Exogenous auxinse3
- Outcome
- total number of LRse3
- Direction
- did not increasee3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cucurbita pepo”
e3“Exogenous auxins did not increase the total number of LRs and did not affect the LRI index”
Claim · model-written summary
Exogenous auxins did not affect the lateral root initiation index.
- Taxon
- Cucurbita pepoCucurbita pepot0
- Treatment
- Exogenous auxinse3
- Outcome
- LRI indexe3
- Direction
- no_changeinferrede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cucurbita pepo”
e3“Exogenous auxins did not increase the total number of LRs and did not affect the LRI index”
Claim · model-written summary
Exogenous auxin transport inhibitors reduced the number of lateral roots formed.
- Taxon
- Cucurbita pepoCucurbita pepot0
- Treatment
- exogenous auxin transport inhibitorse4
- Outcome
- number of LRs formede4
- Direction
- reducede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cucurbita pepo”
e4“Although exogenous auxin transport inhibitors acted in different ways, they all reduced the number of LRs formed”
Claim · model-written summary
A local auxin response maximum before the first anticlinal formative divisions is proposed as the common mechanism of lateral root initiation in flowering plants.
- Taxon
- Cucurbita pepoCucurbita pepot0
- Outcome
- common mechanism underlying LRI in flowering plantse5
- Qualifier
- formation of a local ARM before the first anticlinal formative divisionse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cucurbita pepo”
e5“the formation of a local ARM before the first anticlinal formative divisions is the common mechanism underlying LRI in flowering plants”
Claim · model-written summary
Regulation of root branching is proposed to be independent of the position of the lateral root initiation site relative to the root tip.
- Taxon
- Cucurbita pepoCucurbita pepot0
- Outcome
- regulation of root branchinge6
- Qualifier
- independent of the position of the LRI site relative to the parental root tipe6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cucurbita pepo”
e6“the mechanisms of the regulation of root branching are independent of the position of the LRI site relative to the parental root tip”
The same questions in other papers
class · growth · Cucurbita pepoPositive and negative results
1 in the opposite direction
- positive
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.