Dataset Information

Mechano-chemical aspects of organ formation in Arabidopsis thaliana: the relationship between auxin and pectin.

ABSTRACT: How instructive signals are translated into robust and predictable changes in growth is a central question in developmental biology. Recently, much interest has centered on the feedback between chemical instructions and mechanical changes for pattern formation in development. In plants, the patterned arrangement of aerial organs, or phyllotaxis, is instructed by the phytohormone auxin; however, it still remains to be seen how auxin is linked, at the apex, to the biochemical and mechanical changes of the cell wall required for organ outgrowth. Here, using Atomic Force Microscopy, we demonstrate that auxin reduces tissue rigidity prior to organ outgrowth in the shoot apex of Arabidopsis thaliana, and that the de-methyl-esterification of pectin is necessary for this reduction. We further show that development of functional organs produced by pectin-mediated ectopic wall softening requires auxin signaling. Lastly, we demonstrate that coordinated localization of the auxin transport protein, PIN1, is disrupted in a naked-apex produced by increasing cell wall rigidity. Our data indicates that a feedback loop between the instructive chemical auxin and cell wall mechanics may play a crucial role in phyllotactic patterning.

SUBMITTER: Braybrook SA

PROVIDER: S-EPMC3595255 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Mechano-chemical aspects of organ formation in Arabidopsis thaliana: the relationship between auxin and pectin.

Braybrook Siobhan A SA Peaucelle Alexis A

PloS one 20130312 3

How instructive signals are translated into robust and predictable changes in growth is a central question in developmental biology. Recently, much interest has centered on the feedback between chemical instructions and mechanical changes for pattern formation in development. In plants, the patterned arrangement of aerial organs, or phyllotaxis, is instructed by the phytohormone auxin; however, it still remains to be seen how auxin is linked, at the apex, to the biochemical and mechanical change ...[more]

PMID: 23554870

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Project description:Lateral root (LR) formation is a vital organogenetic process that determines the root architecture in plants. The number of root branches governs the degree of anchorage, efficiency of nutrients acquisition, and water uptake. The molecular pathways involved in LR formation have been extensively studied in Arabidopsis thaliana (At). A plant hormone, Auxin, is a key regulator of root development and promotes LR formation in plants. A plethora of Arabidopsis genes have been identified to regulate LR initiation, patterning, and emergence processes. Recently, the involvement of flowering time control pathways and circadian clock pathways in LR development has come to light, but the connecting link between these processes is still missing. We have established that GIGANTEA (GI), a key component of photoperiodic flowering, can regulate the formation of LRs in Arabidopsis. GI is known to be involved in red light signaling and circadian clock signaling pathways. Here, we report that over-expression of GI enhances LR formation in red light in At. Real-time PCR analysis shows that GI positively regulates the transcription of TRANSPORT INHIBITOR RESPONSE 1 (TIR1) which is an upstream component of auxin signaling. Furthermore, gi-100 mutant downregulates the LR initiation signaling gene, AUXIN RESPONSE FACTOR 7 (ARF7), and its downstream target gene, LATERAL ORGAN BOUNDARIES-DOMAIN 16 (LBD16). Hence, GI acts as a positive regulator of IAA14-ARF7-LBD16 modules during LR initiation. We have also checked the effect of GI on the expression of NAC1 and AIR3 genes which are controlled by TIR1 during LR formation. Our results show that GI induces the NAC1 transcription and its downstream gene, AIR3 expression, which leads to the enhancement of LR initiation. Taken together, our results suggest that GI controls the expression of TIR1 to govern auxin signaling during LR formation in presence of red light and GI can act as a link between circadian clock signaling, flowering time control pathways, light signaling, and lateral root development pathways.

Project description:Background and aimsLATERAL ORGAN BOUNDARIES DOMAIN 29 (LBD29), an important molecule downstream of auxin response factors ARF7 and ARF19, has a critical role in lateral root formation in Arabidopsis thaliana. The cell cycle activation of pericycle cells and their speciﬁcation triggered by auxin are crucial for the initiation of lateral roots. In this study, we attempted to determine whether LBD29 is involved in auxin signalling and/or cell cycle regulation and to characterize the roles of LBD29 in these processes.MethodsThe impact of LBD29 on cell cycling progression in pericycle cells was investigated in lbd29 loss-of-function mutant or LBD29-over-expressing plants. The cell cycle was determined by measuring the expression of some cell cycle-related genes using in situ hybridization and quantitative real-time reverse transcription-PCR (qRT-PCR). Furthermore, the cell division in the root explants from either the lbd29 mutant, LBD29-over-expressing plants or the wild type grown in auxin-rich media was also analysed and compared by the distribution of DR5:β-glucuronidase (GUS) in the primordia or by the expression of PIN-FORMED (PIN) members and PLETHROA 1 (PLT1) which represented the auxin response by the pericycle cells.Key resultslbd29 mutation resulted in reduced numbers of lateral roots and primordia, whereas LBD29 over-expression resulted in more lateral root and primordia formation than in the wild type. More importantly, the level of LBD29 expression was found to be positively correlated with the level of expression of cell cycle-related genes and correlated with the numbers of subcellular organelles found in pericycle cells in the maturation zone. In addition, an in vitro experiment using root explants demonstrated that the presence of LBD29 was required for the maintenance of the cell division capacity of the pericycle. Furthermore, LBD29 appeared to modify PIN-dependent auxin signalling in the primordia since there was a correlated association between the expression of PINs, PLT1 and DR5:GUS and the expression of LBD29.ConclusionsThe ability of LBD29 to regulate lateral root initiation is associated with its maintenance of the cell division capacity of the pericycle in response to auxin and its involvement in the auxin signalling pathway.

Dataset Information

Mechano-chemical aspects of organ formation in Arabidopsis thaliana: the relationship between auxin and pectin.

Publications

Mechano-chemical aspects of organ formation in Arabidopsis thaliana: the relationship between auxin and pectin.

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