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Plant Hormone Homeostasis, Signaling, and Function during Adventitious Root Formation in Cuttings.

Druege U, Franken P, Hajirezaei MR - Front Plant Sci (2016)

Bottom Line: Adventitious root (AR) formation in cuttings is a multiphase developmental process, resulting from wounding at the cutting site and isolation from the resource and signal network of the whole plant.Though, promotive effects of auxins are widely used for clonal plant propagation, the regulation and function of plant hormones and their intricate signaling networks during AR formation in cuttings are poorly understood.Furthermore, the whole cutting should be regarded as a system of physiological units with diverse functions specifically responding to the environment and determining the rooting response.

View Article: PubMed Central - PubMed

Affiliation: Department Plant Propagation, Leibniz Institute of Vegetable and Ornamental Crops Erfurt, Germany.

ABSTRACT
Adventitious root (AR) formation in cuttings is a multiphase developmental process, resulting from wounding at the cutting site and isolation from the resource and signal network of the whole plant. Though, promotive effects of auxins are widely used for clonal plant propagation, the regulation and function of plant hormones and their intricate signaling networks during AR formation in cuttings are poorly understood. In this focused review, we discuss our recent publications on the involvement of polar auxin transport (PAT) and transcriptional regulation of auxin and ethylene action during AR formation in petunia cuttings in a broad context. Integrating new findings on cuttings of other plant species and general models on plant hormone networks, a model on the regulation and function of auxin, ethylene, and jasmonate in AR formation of cuttings is presented. PAT and cutting off from the basipetal auxin drain are considered as initial principles generating early accumulation of IAA in the rooting zone. This is expected to trigger a self-regulatory process of auxin canalization and maximization to responding target cells, there inducing the program of AR formation. Regulation of auxin homeostasis via auxin influx and efflux carriers, GH3 proteins and peroxidases, of flavonoid metabolism, and of auxin signaling via AUX/IAA proteins, TOPLESS, ARFs, and SAUR-like proteins are postulated as key processes determining the different phases of AR formation. NO and H2O2 mediate auxin signaling via the cGMP and MAPK cascades. Transcription factors of the GRAS-, AP2/ERF-, and WOX-families link auxin signaling to cell fate specification. Cyclin-mediated governing of the cell cycle, modifications of sugar metabolism and microtubule and cell wall remodeling are considered as important implementation processes of auxin function. Induced by the initial wounding and other abiotic stress factors, up-regulation of ethylene biosynthesis, and signaling via ERFs and early accumulation of jasmonic acid stimulate AR formation, while both pathways are linked to auxin. Future research on the function of candidate genes should consider their tissue-specific role and regulation by environmental factors. Furthermore, the whole cutting should be regarded as a system of physiological units with diverse functions specifically responding to the environment and determining the rooting response.

No MeSH data available.


Related in: MedlinePlus

Network of ethylene, auxin and jasmonic acid homeostasis and signaling in excision-induced AR formation in Petunia hybrida cuttings. Factors underlying the Key Concepts 1–5 are indicated by specific framing and colors. Green arrows indicate evident and hypothetic (dashed line) factors stimulating IAA and JA accumulation and inducing specific ACS, ACO, and IAA-AAH genes in the rooting zone. Red arrows indicate evident links between PAT, IAA accumulation, invertase activity, cell division and AR formation and hypothetical links (dashed arrows) between the resulting IAA level, transcriptional regulation of plant hormone (PH) action and the two phases of AR formation. Blue arrows indicate the evident link between early JA accumulation and AR formation, while the action on induction and/or formation is still unclear (dashed arrows). PID, PINOID; Me, meristemoids; M, meristems; P, primordia. The scheme integrates the two models of Ahkami et al. (2013) and Druege et al. (2014) and recent results of Lischewski et al. (2015).
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Figure 1: Network of ethylene, auxin and jasmonic acid homeostasis and signaling in excision-induced AR formation in Petunia hybrida cuttings. Factors underlying the Key Concepts 1–5 are indicated by specific framing and colors. Green arrows indicate evident and hypothetic (dashed line) factors stimulating IAA and JA accumulation and inducing specific ACS, ACO, and IAA-AAH genes in the rooting zone. Red arrows indicate evident links between PAT, IAA accumulation, invertase activity, cell division and AR formation and hypothetical links (dashed arrows) between the resulting IAA level, transcriptional regulation of plant hormone (PH) action and the two phases of AR formation. Blue arrows indicate the evident link between early JA accumulation and AR formation, while the action on induction and/or formation is still unclear (dashed arrows). PID, PINOID; Me, meristemoids; M, meristems; P, primordia. The scheme integrates the two models of Ahkami et al. (2013) and Druege et al. (2014) and recent results of Lischewski et al. (2015).

Mentions: On an anatomical scale, AR formation starts with the induction phase, which is devoid of any visible cell divisions, but involves the reprograming of target cells toward the establishment of clusters of new meristematic cells (root meristemoids). The induction phase can be further separated in the early and late phase (da Costa et al., 2013), while the early induction phase may include the dedifferentiation of founder cells as postulated by De Klerk et al. (1999). The induction phase is successively followed by the formation of the dome-shaped root primordia (initiation phase) and by the establishment of vascular connections of the new structures and root emergence (expression phase). For simplification purposes, the initiation and expression phases can be joined under the single domination of formation phase. Whereas ARs in young hypocotyls originate from pericycle cells, ARs in older hypocotyls, non-hypocotyl stems and petioles of detached leaves are initiated in other tissues in close proximity to the vascular tissues, such as phloem or xylem parenchyma cells, or interfascicular cambium cells (da Costa et al., 2013; Bellini et al., 2014). For clonal propagation, the excised leafy tip of an axillary shoot of the donor plant is the structure frequently used as cutting, where the ARs are generated in the non-hypocotyl stem base (Figure 1).


Plant Hormone Homeostasis, Signaling, and Function during Adventitious Root Formation in Cuttings.

Druege U, Franken P, Hajirezaei MR - Front Plant Sci (2016)

Network of ethylene, auxin and jasmonic acid homeostasis and signaling in excision-induced AR formation in Petunia hybrida cuttings. Factors underlying the Key Concepts 1–5 are indicated by specific framing and colors. Green arrows indicate evident and hypothetic (dashed line) factors stimulating IAA and JA accumulation and inducing specific ACS, ACO, and IAA-AAH genes in the rooting zone. Red arrows indicate evident links between PAT, IAA accumulation, invertase activity, cell division and AR formation and hypothetical links (dashed arrows) between the resulting IAA level, transcriptional regulation of plant hormone (PH) action and the two phases of AR formation. Blue arrows indicate the evident link between early JA accumulation and AR formation, while the action on induction and/or formation is still unclear (dashed arrows). PID, PINOID; Me, meristemoids; M, meristems; P, primordia. The scheme integrates the two models of Ahkami et al. (2013) and Druege et al. (2014) and recent results of Lischewski et al. (2015).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814496&req=5

Figure 1: Network of ethylene, auxin and jasmonic acid homeostasis and signaling in excision-induced AR formation in Petunia hybrida cuttings. Factors underlying the Key Concepts 1–5 are indicated by specific framing and colors. Green arrows indicate evident and hypothetic (dashed line) factors stimulating IAA and JA accumulation and inducing specific ACS, ACO, and IAA-AAH genes in the rooting zone. Red arrows indicate evident links between PAT, IAA accumulation, invertase activity, cell division and AR formation and hypothetical links (dashed arrows) between the resulting IAA level, transcriptional regulation of plant hormone (PH) action and the two phases of AR formation. Blue arrows indicate the evident link between early JA accumulation and AR formation, while the action on induction and/or formation is still unclear (dashed arrows). PID, PINOID; Me, meristemoids; M, meristems; P, primordia. The scheme integrates the two models of Ahkami et al. (2013) and Druege et al. (2014) and recent results of Lischewski et al. (2015).
Mentions: On an anatomical scale, AR formation starts with the induction phase, which is devoid of any visible cell divisions, but involves the reprograming of target cells toward the establishment of clusters of new meristematic cells (root meristemoids). The induction phase can be further separated in the early and late phase (da Costa et al., 2013), while the early induction phase may include the dedifferentiation of founder cells as postulated by De Klerk et al. (1999). The induction phase is successively followed by the formation of the dome-shaped root primordia (initiation phase) and by the establishment of vascular connections of the new structures and root emergence (expression phase). For simplification purposes, the initiation and expression phases can be joined under the single domination of formation phase. Whereas ARs in young hypocotyls originate from pericycle cells, ARs in older hypocotyls, non-hypocotyl stems and petioles of detached leaves are initiated in other tissues in close proximity to the vascular tissues, such as phloem or xylem parenchyma cells, or interfascicular cambium cells (da Costa et al., 2013; Bellini et al., 2014). For clonal propagation, the excised leafy tip of an axillary shoot of the donor plant is the structure frequently used as cutting, where the ARs are generated in the non-hypocotyl stem base (Figure 1).

Bottom Line: Adventitious root (AR) formation in cuttings is a multiphase developmental process, resulting from wounding at the cutting site and isolation from the resource and signal network of the whole plant.Though, promotive effects of auxins are widely used for clonal plant propagation, the regulation and function of plant hormones and their intricate signaling networks during AR formation in cuttings are poorly understood.Furthermore, the whole cutting should be regarded as a system of physiological units with diverse functions specifically responding to the environment and determining the rooting response.

View Article: PubMed Central - PubMed

Affiliation: Department Plant Propagation, Leibniz Institute of Vegetable and Ornamental Crops Erfurt, Germany.

ABSTRACT
Adventitious root (AR) formation in cuttings is a multiphase developmental process, resulting from wounding at the cutting site and isolation from the resource and signal network of the whole plant. Though, promotive effects of auxins are widely used for clonal plant propagation, the regulation and function of plant hormones and their intricate signaling networks during AR formation in cuttings are poorly understood. In this focused review, we discuss our recent publications on the involvement of polar auxin transport (PAT) and transcriptional regulation of auxin and ethylene action during AR formation in petunia cuttings in a broad context. Integrating new findings on cuttings of other plant species and general models on plant hormone networks, a model on the regulation and function of auxin, ethylene, and jasmonate in AR formation of cuttings is presented. PAT and cutting off from the basipetal auxin drain are considered as initial principles generating early accumulation of IAA in the rooting zone. This is expected to trigger a self-regulatory process of auxin canalization and maximization to responding target cells, there inducing the program of AR formation. Regulation of auxin homeostasis via auxin influx and efflux carriers, GH3 proteins and peroxidases, of flavonoid metabolism, and of auxin signaling via AUX/IAA proteins, TOPLESS, ARFs, and SAUR-like proteins are postulated as key processes determining the different phases of AR formation. NO and H2O2 mediate auxin signaling via the cGMP and MAPK cascades. Transcription factors of the GRAS-, AP2/ERF-, and WOX-families link auxin signaling to cell fate specification. Cyclin-mediated governing of the cell cycle, modifications of sugar metabolism and microtubule and cell wall remodeling are considered as important implementation processes of auxin function. Induced by the initial wounding and other abiotic stress factors, up-regulation of ethylene biosynthesis, and signaling via ERFs and early accumulation of jasmonic acid stimulate AR formation, while both pathways are linked to auxin. Future research on the function of candidate genes should consider their tissue-specific role and regulation by environmental factors. Furthermore, the whole cutting should be regarded as a system of physiological units with diverse functions specifically responding to the environment and determining the rooting response.

No MeSH data available.


Related in: MedlinePlus