Plant hormone cross-talk: the pivot of root growth

Pacifici, Elena; Polverari, Laura; Sabatini, Sabrina

doi:10.1093/jxb/eru534

Cited by 197 publications

(128 citation statements)

References 97 publications

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“…In addition, the iaa20 iaa30 mutant has wider veins in its cotyledons and longer roots compared with the wild type. Wider cotyledonary and leaf veins are observed in cases of elevated auxin levels, such as under conditions of reduced auxin transport , and longer roots are seen under conditions of suppressed cytokinin signaling and enhanced auxin signaling within the root meristem (Pacifici et al, 2015). Thus, taken together, these phenotypes alone are suggestive of elevated auxin signaling in the iaa20 iaa30 double mutant.…”

Section: Regulation Of Iaa20 and Iaa30 Is Required For Normal Root Vamentioning

confidence: 98%

PHABULOSA Mediates an Auxin Signaling Loop to Regulate Vascular Patterning in Arabidopsis

et al. 2015

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Plant vascular tissues, xylem and phloem, differentiate in distinct patterns from procambial cells as an integral transport system for water, sugars, and signaling molecules. Procambium formation is promoted by high auxin levels activating class III homeodomain leucine zipper (HD-ZIP III) transcription factors (TFs). In the root of Arabidopsis (Arabidopsis thaliana), HD-ZIP III TFs dose-dependently govern the patterning of the xylem axis, with higher levels promoting metaxylem cell identity in the central axis and lower levels promoting protoxylem at its flanks. It is unclear, however, by what mechanisms the HD-ZIP III TFs control xylem axis patterning. Here, we present data suggesting that an important mechanism is their ability to moderate the auxin response. We found that changes in HD-ZIP III TF levels affect the expression of genes encoding core auxin response molecules. We show that one of the HD-ZIP III TFs, PHABULOSA, directly binds the promoter of both MONOPTEROS (MP)/AUXIN RESPONSE FACTOR5, a key factor in vascular formation, and IAA20, encoding an auxin/indole acetic acid protein that is stable in the presence of auxin and able to interact with and repress MP activity. The double mutant of IAA20 and its closest homolog IAA30 forms ectopic protoxylem, while overexpression of IAA30 causes discontinuous protoxylem and occasional ectopic metaxylem, similar to a weak loss-of-function mp mutant. Our results provide evidence that HD-ZIP III TFs directly affect the auxin response and mediate a feed-forward loop formed by MP and IAA20 that may focus and stabilize the auxin response during vascular patterning and the differentiation of xylem cell types.

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Section: Regulation Of Iaa20 and Iaa30 Is Required For Normal Root Vamentioning

confidence: 98%

PHABULOSA Mediates an Auxin Signaling Loop to Regulate Vascular Patterning in Arabidopsis

et al. 2015

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“…Although the latter are considered negative regulators of the cytokinin response, the mechanism by which type-A inhibits type-B has not been fully elucidated, especially at the protein level (Pacifici et al, 2015). Although no direct experimental evidence has been revealed, researchers have proposed that type-A RR proteins may inhibit the activity of type-B RR proteins either by competing for phosphorylation from upstream His-containing phosphotransferases or by forming inactive type-A/B heterodimers (Kim, 2008;Kieber and Schaller, 2014).…”

Section: Osrr1 Delays Flowering By Forming a Heterodimer With Ehd1mentioning

confidence: 99%

Homodimerization of Ehd1 Is Required to Induce Flowering in Rice

et al. 2016

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In plants, flowering time is elaborately controlled by various environment factors. Ultimately, florigens such as FLOWERING LOCUS T (FT) or FT-like molecules induce flowering. In rice (Oryza sativa), Early heading date 1 (Ehd1) is a major inducer of florigen gene expression. Although Ehd1 is highly homologous to the type-B response regulator (RR) family in the cytokinin signaling pathway, its precise molecular mechanism is not well understood. In this study, we showed that the C-terminal portion of the protein containing the GARP DNA-binding (G) domain can promote flowering when overexpressed. We also observed that the N-terminal portion of Ehd1, carrying the receiver (R) domain, delays flowering by inhibiting endogenous Ehd1 activity. Ehd1 protein forms a homomer via a 16-amino acid region in the inter domain between R and G. From the site-directed mutagenesis analyses, we demonstrated that phosphorylation of the Asp-63 residue within the R domain induces the homomerization of Ehd1, which is crucial for Ehd1 activity. A type-A RR, OsRR1, physically interacts with Ehd1 to form a heterodimer. In addition, OsRR1-overexpressing plants show a late-flowering phenotype. Based on these observations, we conclude that OsRR1 inhibits Ehd1 activity by binding to form an inactive complex.

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“…2015; Fisher & Sozzani 2016). Auxin and cytokinin are possibly the best studied cross‐interacting plant hormones, shown to be involved in the establishment and maintenance of the root apical meristem (Ioio et al.…”

Section: Resultsmentioning

confidence: 99%

Externally imposed electric field enhances plant root tip regeneration

2016

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In plants, shoot and root regeneration can be induced in the distinctive conditions of tissue culture (in vitro) but is also observed in intact individuals (in planta) recovering from tissue damage. Roots, for example, can regenerate their fully excised meristems in planta, even in mutants with impaired apical stem cell niches. Unfortunately, to date a comprehensive understanding of regeneration in plants is still missing. Here, we provide evidence that an imposed electric field can perturb apical root regeneration in Arabidopsis. Crucially, we explored both spatial and temporal competences of the stump to respond to electrical stimulation, by varying respectively the position of the cut and the time interval between excision and stimulation. Our data indicate that a brief pulse of an electric field parallel to the root is sufficient to increase by up to two‐fold the probability of its regeneration, and to perturb the local distribution of the hormone auxin, as well as cell division regulation. Remarkably, the orientation of the root towards the anode or the cathode is shown to play a role.

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Plant hormone cross-talk: the pivot of root growth

Cited by 197 publications

References 97 publications

PHABULOSA Mediates an Auxin Signaling Loop to Regulate Vascular Patterning in Arabidopsis

PHABULOSA Mediates an Auxin Signaling Loop to Regulate Vascular Patterning in Arabidopsis

Homodimerization of Ehd1 Is Required to Induce Flowering in Rice

Externally imposed electric field enhances plant root tip regeneration

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