Limits...
Sl-IAA3, a tomato Aux/IAA at the crossroads of auxin and ethylene signalling involved in differential growth.

Chaabouni S, Jones B, Delalande C, Wang H, Li Z, Mila I, Frasse P, Latché A, Pech JC, Bouzayen M - J. Exp. Bot. (2009)

Bottom Line: Sl-IAA3 expression is auxin and ethylene dependent, is regulated on a tight tissue-specific basis, and is associated with tissues undergoing differential growth such as in epinastic petioles and apical hook.Antisense down-regulation of Sl-IAA3 results in auxin and ethylene-related phenotypes, including altered apical dominance, lower auxin sensitivity, exaggerated apical hook curvature in the dark and reduced petiole epinasty in the light.The results provide novel insights into the roles of Aux/IAAs and position the Sl-IAA3 protein at the crossroads of auxin and ethylene signalling in tomato.

View Article: PubMed Central - PubMed

Affiliation: Université de Toulouse, INP-ENSA Toulouse, Génomique et Biotechnologie des Fruits, Avenue de l'Agrobiopole BP 32607, Castanet-Tolosan F-31326, France.

ABSTRACT
Whereas the interplay of multiple hormones is essential for most plant developmental processes, the key integrating molecular players remain largely undiscovered or uncharacterized. It is shown here that a member of the tomato auxin/indole-3-acetic acid (Aux/IAA) gene family, Sl-IAA3, intersects the auxin and ethylene signal transduction pathways. Aux/IAA genes encode short-lived transcriptional regulators central to the control of auxin responses. Their functions have been defined primarily by dominant, gain-of-function mutant alleles in Arabidopsis. The Sl-IAA3 gene encodes a nuclear-targeted protein that can repress transcription from auxin-responsive promoters. Sl-IAA3 expression is auxin and ethylene dependent, is regulated on a tight tissue-specific basis, and is associated with tissues undergoing differential growth such as in epinastic petioles and apical hook. Antisense down-regulation of Sl-IAA3 results in auxin and ethylene-related phenotypes, including altered apical dominance, lower auxin sensitivity, exaggerated apical hook curvature in the dark and reduced petiole epinasty in the light. The results provide novel insights into the roles of Aux/IAAs and position the Sl-IAA3 protein at the crossroads of auxin and ethylene signalling in tomato.

Show MeSH

Related in: MedlinePlus

Expression of PIAA3::GUS is associated with differential growth during hook formation and leaf epinastic response. (A) Tissue-specific expression of PIAA3::GUS and DR5::GUS in etiolated seedlings. PIAA3::GUS and DR5::GUS seedlings were dark-grown for 5 d and then treated for 48 h with air or 10 μl l−1 of ethylene in absence (left panel) or presence of NPA (right panel). The upper-panel shows the ethylene-dependent GUS staining in the apical hook of PIAA3::GUS tomato plants. The lower-panel shows GUS staining in the DR5::GUS-transformed plants used for detection of active auxin signalling in the hook. Inserts correspond to the expression of PIAA3::GUS and DR5::GUS in the root caps following ethylene treatment. (B) Expression of PIAA3::GUS in epinastic petioles. Six-week-old light-grown plants were placed in airtight chambers for 16 h in the absence (upper-panel) or presence (lower-panel) of 50 μl l−1 of ethylene. The arrows indicate the expression of GUS in the leaf nodes of the petiole. The images are representative of at least three independent experiments with n > 30 seedlings per experiment.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2657550&req=5

fig8: Expression of PIAA3::GUS is associated with differential growth during hook formation and leaf epinastic response. (A) Tissue-specific expression of PIAA3::GUS and DR5::GUS in etiolated seedlings. PIAA3::GUS and DR5::GUS seedlings were dark-grown for 5 d and then treated for 48 h with air or 10 μl l−1 of ethylene in absence (left panel) or presence of NPA (right panel). The upper-panel shows the ethylene-dependent GUS staining in the apical hook of PIAA3::GUS tomato plants. The lower-panel shows GUS staining in the DR5::GUS-transformed plants used for detection of active auxin signalling in the hook. Inserts correspond to the expression of PIAA3::GUS and DR5::GUS in the root caps following ethylene treatment. (B) Expression of PIAA3::GUS in epinastic petioles. Six-week-old light-grown plants were placed in airtight chambers for 16 h in the absence (upper-panel) or presence (lower-panel) of 50 μl l−1 of ethylene. The arrows indicate the expression of GUS in the leaf nodes of the petiole. The images are representative of at least three independent experiments with n > 30 seedlings per experiment.

Mentions: To get more insight on the role of Sl-IAA3 in apical hook formation and epinastic response, the expression pattern of this gene was analysed in tomato lines expressing the PIAA3::GUS construct. In the absence of exogenous ethylene treatment there was minimal GUS staining associated with the apical hook in dark-grown wild-type PIAA3::GUS lines. By contrast, after 48 h ethylene treatment (10 μl l−1), a strong band of GUS staining was observed on the inner surface of the apical hook (Fig. 8A). The same ethylene treatment did not result in detectable DR5-driven GUS staining in the hook. The putative role of auxin in mediating the ethylene-associated expression of Sl-IAA3 was then investigated by performing the ethylene treatment in the presence of NPA, a known inhibitor of auxin transport. NPA completely prevented ethylene-induced apical hook formation and simultaneously suppressed Sl-IAA3 expression, suggesting that auxin is required for apical hook formation and for the expression of IAA3 in the inner side of the hook. Noteworthy, upon ethylene treatment, intense staining was present in the root tips of both transgenic lines, attesting that DR5 and IAA3 promoters exhibit similar capacity to drive GUS activity in tissues accumulating high amounts of auxin. Taken together these data suggest that the higher ethylene-induced expression of Sl-IAA3 in the inner side of the apical hook could not be ascribed only to increased auxin levels (Fig. 8A).


Sl-IAA3, a tomato Aux/IAA at the crossroads of auxin and ethylene signalling involved in differential growth.

Chaabouni S, Jones B, Delalande C, Wang H, Li Z, Mila I, Frasse P, Latché A, Pech JC, Bouzayen M - J. Exp. Bot. (2009)

Expression of PIAA3::GUS is associated with differential growth during hook formation and leaf epinastic response. (A) Tissue-specific expression of PIAA3::GUS and DR5::GUS in etiolated seedlings. PIAA3::GUS and DR5::GUS seedlings were dark-grown for 5 d and then treated for 48 h with air or 10 μl l−1 of ethylene in absence (left panel) or presence of NPA (right panel). The upper-panel shows the ethylene-dependent GUS staining in the apical hook of PIAA3::GUS tomato plants. The lower-panel shows GUS staining in the DR5::GUS-transformed plants used for detection of active auxin signalling in the hook. Inserts correspond to the expression of PIAA3::GUS and DR5::GUS in the root caps following ethylene treatment. (B) Expression of PIAA3::GUS in epinastic petioles. Six-week-old light-grown plants were placed in airtight chambers for 16 h in the absence (upper-panel) or presence (lower-panel) of 50 μl l−1 of ethylene. The arrows indicate the expression of GUS in the leaf nodes of the petiole. The images are representative of at least three independent experiments with n > 30 seedlings per experiment.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2657550&req=5

fig8: Expression of PIAA3::GUS is associated with differential growth during hook formation and leaf epinastic response. (A) Tissue-specific expression of PIAA3::GUS and DR5::GUS in etiolated seedlings. PIAA3::GUS and DR5::GUS seedlings were dark-grown for 5 d and then treated for 48 h with air or 10 μl l−1 of ethylene in absence (left panel) or presence of NPA (right panel). The upper-panel shows the ethylene-dependent GUS staining in the apical hook of PIAA3::GUS tomato plants. The lower-panel shows GUS staining in the DR5::GUS-transformed plants used for detection of active auxin signalling in the hook. Inserts correspond to the expression of PIAA3::GUS and DR5::GUS in the root caps following ethylene treatment. (B) Expression of PIAA3::GUS in epinastic petioles. Six-week-old light-grown plants were placed in airtight chambers for 16 h in the absence (upper-panel) or presence (lower-panel) of 50 μl l−1 of ethylene. The arrows indicate the expression of GUS in the leaf nodes of the petiole. The images are representative of at least three independent experiments with n > 30 seedlings per experiment.
Mentions: To get more insight on the role of Sl-IAA3 in apical hook formation and epinastic response, the expression pattern of this gene was analysed in tomato lines expressing the PIAA3::GUS construct. In the absence of exogenous ethylene treatment there was minimal GUS staining associated with the apical hook in dark-grown wild-type PIAA3::GUS lines. By contrast, after 48 h ethylene treatment (10 μl l−1), a strong band of GUS staining was observed on the inner surface of the apical hook (Fig. 8A). The same ethylene treatment did not result in detectable DR5-driven GUS staining in the hook. The putative role of auxin in mediating the ethylene-associated expression of Sl-IAA3 was then investigated by performing the ethylene treatment in the presence of NPA, a known inhibitor of auxin transport. NPA completely prevented ethylene-induced apical hook formation and simultaneously suppressed Sl-IAA3 expression, suggesting that auxin is required for apical hook formation and for the expression of IAA3 in the inner side of the hook. Noteworthy, upon ethylene treatment, intense staining was present in the root tips of both transgenic lines, attesting that DR5 and IAA3 promoters exhibit similar capacity to drive GUS activity in tissues accumulating high amounts of auxin. Taken together these data suggest that the higher ethylene-induced expression of Sl-IAA3 in the inner side of the apical hook could not be ascribed only to increased auxin levels (Fig. 8A).

Bottom Line: Sl-IAA3 expression is auxin and ethylene dependent, is regulated on a tight tissue-specific basis, and is associated with tissues undergoing differential growth such as in epinastic petioles and apical hook.Antisense down-regulation of Sl-IAA3 results in auxin and ethylene-related phenotypes, including altered apical dominance, lower auxin sensitivity, exaggerated apical hook curvature in the dark and reduced petiole epinasty in the light.The results provide novel insights into the roles of Aux/IAAs and position the Sl-IAA3 protein at the crossroads of auxin and ethylene signalling in tomato.

View Article: PubMed Central - PubMed

Affiliation: Université de Toulouse, INP-ENSA Toulouse, Génomique et Biotechnologie des Fruits, Avenue de l'Agrobiopole BP 32607, Castanet-Tolosan F-31326, France.

ABSTRACT
Whereas the interplay of multiple hormones is essential for most plant developmental processes, the key integrating molecular players remain largely undiscovered or uncharacterized. It is shown here that a member of the tomato auxin/indole-3-acetic acid (Aux/IAA) gene family, Sl-IAA3, intersects the auxin and ethylene signal transduction pathways. Aux/IAA genes encode short-lived transcriptional regulators central to the control of auxin responses. Their functions have been defined primarily by dominant, gain-of-function mutant alleles in Arabidopsis. The Sl-IAA3 gene encodes a nuclear-targeted protein that can repress transcription from auxin-responsive promoters. Sl-IAA3 expression is auxin and ethylene dependent, is regulated on a tight tissue-specific basis, and is associated with tissues undergoing differential growth such as in epinastic petioles and apical hook. Antisense down-regulation of Sl-IAA3 results in auxin and ethylene-related phenotypes, including altered apical dominance, lower auxin sensitivity, exaggerated apical hook curvature in the dark and reduced petiole epinasty in the light. The results provide novel insights into the roles of Aux/IAAs and position the Sl-IAA3 protein at the crossroads of auxin and ethylene signalling in tomato.

Show MeSH
Related in: MedlinePlus